HomeMy WebLinkAboutTISGuidelines2020MULTIMODAL TRANSPORTATION
IMPACT STUDY GUIDELINES
June 2020
2nd Edition
City of San Luis Obispo 2035 Circulation Element
iTransportationImpactStudyGuidelines
June 2020
TABLE OF CONTENTS
I. Introduction ...................................................................................................................1
Process ...............................................................................................................................1
When Transportation Impact Studies Are Required ...............................................................2
Transportation Impact Study Scoping ...................................................................................2
II. Baseline Conditions ........................................................................................................4
Existing Volumes .................................................................................................................4
Cumulative Volumes ...........................................................................................................5
Project Volumes ..................................................................................................................6
III. Form & Content of Impact Study Document ....................................................................6
IV. CEQA Analysis Methods and SIgnificance Thresholds .......................................................8
Vehicle Miles Traveled ........................................................................................................8
Traffic Safety & Access Management .................................................................................. 12
Consistency with Adopted Policy & Plan for CEQA Analysis .................................................. 13
V. Multimodal Traffic Operations Analysis Methods & Policy Assessment .......................... 13
Multimodal Level of Service and Capacity ........................................................................... 14
Analysis Software .............................................................................................................. 14
Neighborhood Traffic Analysis ........................................................................................... 18
Moda l Priorities ................................................................................................................ 18
VI. Addressing CEQA Impacts and Operational Deficiencies for Local Policy Conformance .... 19
Approach .......................................................................................................................... 19
CEQA Mitigation Strategies for VMT Impacts ...................................................................... 19
Strategies for Addressing Local Policy Deficiencies .............................................................. 20
Equitable Share Responsibility ........................................................................................... 21
Appendices:
A. VMT Screening Maps
B. SLO TDM Technical Guide - Calculating VMT (Cambridge Systematics)
WARNING TO PRACTITIONERS**
Please contact the City Transportation Division before initiating preparation of a
transportation impact study to confirm that you are using the latest edition of these guidelines
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I. INTRODUCTION
The City of San Luis Obispo’s General Plan 2035 Circulation Element establishes key
transportation policies to accommodate growth and balance travel modes. Compared to older
versions of the Circulation Element, t he 2035 Circulation Element places greater e mphasis on
bicycles, pedestrians and transit in order to achieve a system of complete streets and a
multimodal community. Transportation Impact Studies (TIS) are a critical component of the
development review process, including but not limited to studies required under the California
Environmental Quality Act (CEQA). In ad dition to the City’s general plan policies , Senate Bill 743
established changes to how transportation impacts are measured for CEQA purposes, shifting
from auto Level of Service (LOS) and other congestion-related metrics, to analysis of vehicle
miles travelled (VMT) as the primary metric for evaluating transportation impacts . These
guidelines prescribe the methodologies for conducting Transportation Impact Analyses under
both CEQA criteria consistent with SB743 and separate operational policy analysis, whic h is not
subject to CEQA.
These guidelines are periodically updated to reflect changes in City policies, the regulatory
environment, industry best practices for the evaluation of transportation impacts .
Process
Due to potential conflicts of interest private development applicants are not permitted to
conduct or commission their own official Transportation Impact Studies. However, private
development applicants are welcome to conduct or commission peer review and comment on
City-initiated studies before the documentation is finalized.
When a development application or infrastructure project is submitted, the City of San Luis
Obispo’s Transportation Department will determine whether or not a transportation study is
required based on CEQA guidelines and City policy. If a transportation impact study is required,
the study should be initiated with the following steps .
1. City notifies applicant of transportation study requirement as part of comments on
application.
2. Applicant submits a request to the City to initiate the study and City staff drafts a scope
of work.
3. City staff advertises the scope of work among the City’s certified on-call traffic
consultants which are selected bi-annually thru a competitive RFQ/RFP process.
4. City staff selects a traffic consultant based on their proposal, schedule, and cost
estimate.
5. City staff submits the scope, consultant proposal, and draft reimbursement agreement
to the applicant for review and approval.
6. The applicant signs the reimbursement agreement, deposits the funds with t he City, and
work on the study begins.
A 30% City administrative fee is applied to the consultant ’s total cost estimate, with any
remaining funds at the end of the contract refunded to applicant. If out of scope work is needed
during the course of the study, an amendment to the consultant’s proposal and applicant’s
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reimbursement agreement is required. The Transportation Manager at their sole discretion may
apply a time & materials administrative fee in lieu of the 30% in special circumstances.
When Transportation Impact Studies Are Required
The decision to require a Transportation impact study will be made by the City’s Transportation
Manager. Traffic impact studies, either as part of environmental impact reports or a s part of
local policy analysis, must be prepared by a registered Traffic Engineer (TE), Certified
Professional Traffic Operations Engineer (PTOE), or Certified Transportation Planner (PTP or
AICP CTP). Traffic impact studies may be prepared by a registere d Civil Engineer (PE) that has
demonstrated appropriate expertise to the satisfaction of the Transportation Manager.
Transportation impact studies are required whenever there is the potential for inconsistency
with local transportation policy or a potentia l impact under CEQA. The following are examples of
when a Transportation Impact Study maybe required.
Any project that has the potential to increase regional VMT beyond adopted thresholds.
Any project that would generate 100 or more peak hour automobile trips or 150 or
more peak hour person trips.
Any project that increases density where the prior use(s) generated less than 100 peak
hour automobile trips or 150 peak hour person trips and the existing + proposed use
exceeds this peak hour trip threshold.
An y project that proposes frontage improvements, new or modified access points, or
adds trips to an intersection in a manner that could increase or exacerbate the
propensity for traffic collisions based on adopted standards and best practices.
Any project that has the potential to degrade bicycle , p edestrian, transit or auto level of
service standards below City adopted minimums.
Any project that would generate transit demand beyond current service capacities.
Any project that is inconsistent with adopted Tra nsportation Plan, policy, or standard.
When the original impact study is more than two years old.
Transportation Impact Study Scoping
Depending on the scale and extent of the proposed project , the scope of a transportation
impact study could range from a focused study, such as a simple intersection control type
selection analysis for a proposed intersection, to a large-scale study, such as a complete analysis
of all transportation facilities wi thin a defined study area. The impact study scope will be drafted
by the City and collaboratively reviewed and refined by traffic consultant, applicant teams, and
other affected public agencies. Advanced analysis such as travel demand model updates, project
specific trip generation rate development, and micro simulation may be required for certain
studies.
Extents of Study
The TIS study area should include transportation facilities that could reasonably be foreseen to
be impacted by physical changes or trips generated by the project. This is generally determined
by conducting an initial trip generation and distribution assessment to gauge the volume and
extent of traffic a project would generate . A general rule of thumb for scoping st udy
intersections and roadway segments is to include any facilities where a proposed project would
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add 10 or more peak hour auto, bike or pedestrian trips per lane. City staff will prepare an initial
scope of work on a project-by-project basis and identify the preliminary extents of the study, in
consultation with other affected public agencies, for the purposes of advertising and awarding
the traffic impact study contract.
Once the authorization to proceed has been given t he first order of work for the consultant
team is to conduct a refined trip generation estimate, select zone analysis using the City’s Travel
Demand Model (SLO TDM), and recommend to City staff any modifications to the scope based
on a preliminary assessment of the volume and distribution of project traffic.
Any modifications will be formalized through a development services amendment with the
project applicant.
Analysis Scenarios
Analysis scenarios shall be determined on a case -by-case basis depending on the unique
characteristic s of each project. Each scenario will include an evaluation of multimodal
intersection and roadway segment LOS, induced traffic and safety analysis. VMT analysis will be
conducted for the analysis scenario consistent with current CEQA Guideli nes and technical
direction published by the California Governor’s Office of Planning and Research. If the project
as the potential to impact neighborhood traffic thresholds or modal priorities as established in
the City’s general plan an analysis of those will also be required:
1. Existing Conditions – The most recent available traffic conditions and existing
transportation network.
2. Existing + Project Conditions – Existing Conditions plus project-generated trips and
changes to the transportation network.
3. Cumulative Conditions – Future year traffic conditions reflecting land use and
transportation improvements anticipated to be complete with build out of the City’s
General Plan.
4. Cumulative + Project Conditions – Cumulative Conditions plus project-generated traffic
and changes to the transportation network.
Near term analysis maybe scoped for individual project s as deemed necessary when significant
near term development or infrastructure improvements are planned within the vicinity of the
project.
Analysis Periods
The determination of time periods for operational analysis will depend on the travel modes
being evaluated and the time periods that are most applicable to the uses proposed in the
project. For most uses, the analysis may include daily, pea k period, and/or peak hour conditions.
Final determination shall be made in consultation with City staff. For recreational or other uses
that do not coincide with typical weekday peak hours, consideration will be given to analyzing
weekday afternoon, weekday late evening, or weekend time periods. Based on the land use of
the proposed project and upon consultation with City, the study shall analyze traffic operations
during the peak hour of the following time periods:
Weekday morning peak (7:00 – 9:00 AM)
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Weekday evening peak (4:00 – 6:00 PM)
For some projects, the City may substitute or require additional peak hour analysis for the
following time periods:
Weekday afternoon peak (2:00 – 4:00 PM)
Friday evening peak (5:00 – 7:00 PM)
Weekend midday peak (11:00 AM – 1:00 PM)
Weekend evening peak (4:00 – 7:30 PM)
The determination of study time periods should be made separately for each proposed project
based upon the peaking characteristics of project -generated traffic and peaking characteristics
of the adjacent street system and land uses. The time period(s) that should be analyzed are
those that exhibit the maximum combined level of project -generated traffic and adjacent street
traffic.
II. BASELINE CONDITIONS
The City of San Luis Obispo’s Transportation Division ma intains a master Synchro Network of
existing AM, MID, and NOON peak hour conditions for most existing intersections within the
City. This network is generally updated for geometric, signal timing and multimodal volumes
every two years. This master network is the primary source of peak hour transportation data to
be used for impact studies. The City also collects 48 -hour segment counts on most roadways
within the City. Data at specific locations not already collected by the City will need to be
collected as part of individual impact studies, consultants should inventory what data is already
available and scope any necessary data collection.
Existing Volumes
Average Daily Traffic (ADT) segment counts are collected in 15 - or 5-minute intervals for a
period of no less than 48 hours. Volumes used for segment analysis should be based on the
average of the entire count period. Peak hour intersection movement counts are collected in 15-
minute intervals during the required peak hours identified from the segment counts. All traffic
volumes are collected during clear environmental conditions, during regular school session, with
no adjacent construction activities or spe cial events. It is the responsibility of the consultant to
validate traffic counts prior to their use in the analysis. Unless otherwise approved by the
Transportation Manager, traffic data used for transportation impact analyses shall be no more
than two years old at the time the study is initiated.
Vehicle Volumes
Peak hour intersection vehicle movements are collected in UTDF (Universal Traffic Data Format).
In order to calculate pedestrian intersection levels of service, intersections with
protected/permissive phasing shall have the volume of permissive left turns by each left turn
movement counted in addition to the total left turn volumes. At intersections where right turns
on red (RTOR) are permitted, the volume of right turns on red by each right turn movement
counted in addition to the total of right turn volumes. If any form of testing or research indicates
pedestrian LOS is not sensitive to the expected volume of permissive left or right turn on red
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movements, these volumes may be estimated based on professional judgment in lieu of
counting.
Bicycle Volumes
Peak hour intersection bicycle volumes are collected by the approach direction to the
intersection (i.e. EB, WB, NB, SB). If any form of testing or research indicates that bicycle LOS is
not sensitive to the expected volume of bicycles, these volumes may be estimated based on
field observations and professional judgment in lieu of counting.
Pedestrian Volumes
Segment pedestrian flow rates can either be counted or estimated based upon adjacent peak
hour intersection movements. Pedestrian movements shown in the figure below need to be
counted or estimated in order to calculate pedestrian level of service. If any form of testing or
research shows that pedestrian LOS is not sensitive to the expected ped estrian volumes, these
volumes may be estimated based on field observations and professional judgment in lieu of
counting.
Figure 1: Peak Hour Pedestrian Volumes Should Be Collected for All Movements
Cumulative Volumes
The City of San Luis Obispo’s Transportation Division maintains a Cumulative Year scenario
within the SLO TDM TransCAD model, which reflects forecasted build out of the City and region
2035 for City SOI, 2040 for remaining County areas). ADT and Peak Hour multimo dal volumes
are to be derived from this model consistent with forecasting methods established in NCHRP
255. This model is only a tool for estimating future volumes, professional judgment shall be used
in determining the appropriate estimates to be used in the technical analysis. Any assumptions
or modification to model inputs or outputs should be explicitly documented in final reports.
Vehicle, Bicycle, and Pedestrian Volumes
Daily and Peak hour segment & intersection volumes are to be estimated based on the results of
the model forecast and “Process Turns” tool embedded within the model and calibrated as
necessary based on professional judgement. In addition right turn on red, permissive left turns,
and permissive right turns shall be estimated based on the proportionality of those movements
in the existing counts with projected traffic counts. Manual adjustments to the volumes
produced by the travel demand model shall be reviewed and documented as appropriate.
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Project Volumes
Vehicle Volumes
Motor vehicle t rip generation is to be estimated using the most recent edition of ITE Trip
Generation Manual. Upon approval from the Transportation Manager, local trip generation
rates are also acceptable and preferred if those rates are developed following the method
established in the current version of the ITE Trip Generation Handbook and appropriate
validation is provided to support them.
Pedestrian, Bicycle, and Transit Volumes
Non automobile trips shall be calculated by first estimating person trips based on ITE ve hicle trip
generation and average vehicle occupancy rates. Mode split assumptions should be derived
based on data from the SLO TDM, US Census or American Community Survey, and existing
multimodal traffic counts within the vicinity of the proposed project.
Project Trip Distribution
Project trip distribution should be derived from the SLO TDM by conducting a select zone
analysis of the TAZ in which the project is contained. In some cases, trip distribution may need
to be estimated manually, such as when estimating trip distribution for pedestrian and bicycles,
in these cases the assumptions and methodology must be documented in the report.
III. FORM & CONTENT OF IMPACT STUDY DOCUMENT
Per SB 743, auto LOS or other measures of traffic congestion or delay are no longer acceptable
metrics for analysis of transportation impacts under CEQA. However, the City General Plan
Circulation Element will continue to retain local performance threshold s based on multimodal
LOS and analysis of motor vehicle traffic operations will continue to be required outside of CEQA
analysis for purposes of assessing conformity with local policies and to guide transportation
system and access planning. For this reaso n, transportation impact studies shall be divided into
two components:
Part 1: CEQA Transportation Impact Analysis
Part 2: Multimodal Traffic Operations Report and Policy Assessment
The typical format and content required for an impact study is summarized as follows:
Introduction
I. Executive Summary
a. Project Description and Study Scenarios
b. Summary Table of CEQA Impacts & Mitigations
c. Summary Table of Multimodal Operational Deficiencies & Recommended
Conditions of Approval to Offset Deficiencies
II. Table of Contents
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PART 1: CEQA Transportation Impact Analysis
III. Project Description
a. Project Location, Land Uses, Phasing & Site Plan
b. Proposed Frontage Geometrics & Access and Internal Circulation
IV. CEQA Transportation Analysis
a. Environmental Setting
i. Describe Existing Study Area Circulation Network (Existing Roadways,
Pedestrian, Bicycle and Transit Facilities)
ii. Reference applicable local, regional and state plans and regulatory
policies
iii. Analysis Assumptions, Methodologies and CEQA Thresholds of
Significance
b. VMT Analysis
c. CEQA Safety Analysis (per CEQA Guidelines)
d. Assessment of Emergency Vehicle Access
e. Assess Conflicts with Applicable Plans, Programs, Ordinances
f. Induced Travel Analysis of Auto Capacity increasing project components
V. CEQA Conclusions and Recommendations
a. Summary of potentially significant CEQA impacts and proposed mitigations
b. Summary of Measures of Effectiveness before and after mitigation
c. Cost Estimates and Fair Share Calculations for Mitigation (if applicable)
PART 2: Multimodal Traffic Operations Analysis & Policy Assessment
VI. Operations Analysis Approach
a. Analysis Scenarios
b. Study Facilities
c. Assumptions, Methodologies and Local Thresholds of Significance
VII. Baseline Analysis (Existing, Near Term, Cumulative)
a. Intersection & Roadway Geometrics
b. Intersection & Roadway Volumes
c. LOS Analysis
iv. Intersections (Auto, Bike, Ped)
v. Segments (Auto, Bike, Ped, Transit)
d. Intersection Queueing
VIII. Project Analysis (Existing+Project, Near Term+Project, Cumulative+Project)
a. Project Traf fic Generation by Mode
b. Project Trip Distribution & Assignment
c. Intersection & Roadway Geometrics
d. Intersection & Roadway Volumes
e. LOS Analysis
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vi. Intersections (Auto, Bike, Ped)
vii. Segments (Auto, Bike, Ped, Transit)
f. Intersection Queuing
g. Traffic Safety & Access Management Analysis (per local guidelines)
h. Neighborhood Traffic Analysis
IX. Operations Analysis Conclusions and Recommendations
a. Summary of changes in multimodal traffic operations
b. Proposed improvements/actions to offset project -related deficiencies
c. Cost Estimates and Fair Share Calculations for Mitigation (if scoped)
X. Appendices
d. Traffic Data Summary and Source
e. Worksheets Used in Analysis
IV. CEQA ANALYSIS METHODS AND SIGNIFICANCE THRESHOLDS
The following section describes analysis methods and significance th resholds for evaluation of
transportation impacts under CEQA. These analyses inform Part 1 of the final Transportation
Impact Study document: CEQA Transportation Impact Analysis.
Vehicle Miles Traveled
VMT analysis shall be consistent with current CEQA Gui delines, latest SB 743 Technical
Advisories published by the California OPR, and per City standards as described below. All
quantitative VMT analysis shall be conducted using the City of San Luis Obispo Travel Demand
Model (TDM). Alternate analysis tools, such as the SLOCOG TDM or sketch planning tools, shall
only be used at the approval of the Transportation Manager.
Baseline VMT
Baseline (without project) VMT shall be de rived using the latest SLO TDM base year land use and
transportation network inputs. Appendix B includes technical guidance for extracting VMT from
the SLO TDM. Baseline VMT data shall be summarized as follows:
All Projects
o Total Regional (County) VMT
Residential Development Projects (Single-Family, Multi-Family, Mobile Homes)
o Regional (County) average Residential VMT Per Capita (home-based trip
productions only)
Employment-Based Development (Office, Industrial, Manufacturing, etc.)
o Regional (County) average Work VMT Per Employee (home-based work
attractions only)
Where proposed land use projects are inconsistent with currently adopted City and Regional
long-term plans, such as the City General Plan or SLOCOG Regional Transportation Plan (RTP)
and Sustainable Communities Strategy (SCS), baseline Cumulative VMT , calculated using the SLO
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TDM, may also be required for evaluating Cumulative land use and transportation network
impacts.
Attachment A contains detailed guidance for extracting VMT data from the SLO TDM.
VMT Impact Analysis for Land Use Projects
Per OPR guida nce, land use projects that meet the following screening thresholds may be
assumed to result in a less-than-significant transportation impact under CEQA, and will not
require a detailed quantitative VMT assessment.
Screening Criteria for Land Use Projects Exempt from VMT Analysis
Project Type OPR Recommended Threshold
Small
Development
Projects
Projects anticipated to generate < 110 daily vehicle trips (11 peak hour vehicle trips)
may be assumed to cause a less -than-significant impact, unless substantial evidence
indicates that a project would generate a potentially significant level of VMT or create
inconsistency with the SLOCOG RTP Sustainable Communities Strategy (SCS).
Medium-Sized
Residential &
Employment-
Based (Office,
Business Park,
Industrial, etc.)
Development
Projects
Map-based screening may be used for projects that generate < 100 peak hour vehicle
trips. Baseline VMT per capita/employee heat maps are developed based on data
from the SLO TDM, showing existing average Residential and Work VMT for each area
of the City. (See Appendix A for VMT Screening Maps)
Where proposed projects that generate < 100 peak hour trips are located within areas
of the map with existing VMT at least 10% below adopted thresholds, and are
generally similar to existing uses within that area (i.e. density, mix of uses, access to
multimodal transportation), these projects can be assumed to cause a less -than-
significant transportation impacts.
Local Serving
Retail & Public
Facilities
Retail development projects with 50,000 sqft. gross floor area with reasonable
justification that uses will be local -serving may be assumed to cause a less -than-
significant impact.
Similarly, local-serving public facilities, such as Police and Fire Stations, libraries,
neighborhood parks without sporting fields, etc., may be assumed to cause a less -
than-significant impact.
Affordable
Housing
Adding affordable housing in infill locations generally improves jobs -housing balance,
in turn shortening commutes and reducing VMT. A project consisting of a high
percentage of affordable housing (>50%) may be assumed to cause a less -than-
significant impact on VMT if located within a low-VMT area per the City’s VMT
screening maps (see Appendix A) or where supporting evidence is provided that
demonstrates low VMT-generating characteristics of similar affordable housing sites
within the City.
Transit-Oriented
Development2
Per CEQA Guidelines, residential, retail, office and mixed -use projects that are located
within a ½ mile of an existing major transit stop or an existing stop along a high -
quality transit corridor may be assumed to cause a less -than-significant impact on
VMT (see Note 2 below). If project -specific or location-specific information indicates
that the project would still generate significant levels of VMT, focused VMT analysis
may still be required. No locations within the City of San Luis Obispo currently mee t
these transit service levels.
Notes:
1. A “major transit stop” is defined as a site containing an existing rail station, a ferry terminal serviced by bus or
rail transit, or the intersection of two or more major bus routes with a frequency of 15 minutes o r less during
commute periods. A “high-quality transit corridor” refers to a corridor with fixed -route bus service with
frequencies of 1 minutes or less during peak commute hours.
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VMT screening maps for residential and employment-based development projects are provided
in Appendix A.
For land use projects that cannot be screened from requiring VMT analysis, Existing + Project
VMT shall be estimated using the base year SLO TDM and summarized as follows:
Residential Development Projects (Single-Family, Multi-Family, Mobile Homes)
o Net VMT Increase/Decrease with Project
o Project Residential VMT Per Capita (home-based trip productions only)
Employment-Based Development (Office, Industria l, Manufacturing, etc.)
o Net VMT Increase/Decrease with Project
o Project Work VMT Per Employee (home-based work trip attractions only)
Mixed-Use Development Project (include internal capture reductions)
o Summarize Residential and Work VMT as shown above
o Summarize Net Increase/Decrease in Retail VMT
All Other Projects
o Total City VMT (use City Limits, not total City Sphere of Influence)
o Total Regional (County) VMT
o Net VMT Increase/Decrease with Project
Project VMT impacts shall be determined based on the following thresholds of significance:
VMT Thresholds of Significance for Land Use Projects
Project Type Evaluation Criteria Threshold1
Residential 15% below baseline Regional (County) average
Residential VMT per capita. Applies to single-family,
multi-family and mobile homes
14.25 VMT per capita
Office / Business
Park / Industrial /
Warehousing /
Manufacturing
15% below existing regional (County) average Work
VMT per employee.
12.45 VMT per employee
Retail /
Hotel /
School
Net increase in total Regional (County) VMT. Small
local-serving retail may be presumed to cause less -
than-significant impacts. Larger, regional-serving
retail will require quantitative analysis using the
SLO TDM and project-specific information, such as
market studies or analysis of anticipated customer
travel behavior.
No set threshold, increase
in total VMT would trigger
impact
Mixed-Use Evaluate each component of a mixed-use project
independently, applying significance threshold for
each land use type. Alternately, the City may
choose to analyze VMT for only the dominant use.
Analysis should take credit for internal capture
between uses.
Apply Residential, Office &
Retail Thresholds above
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Project Type Evaluation Criteria Threshold1
Redevelopment
Projects
Where a development replaces an existing VMT-
generating land use, if the replacement total VMT
leads to a net overall decrease in VMT, the project
is assumed to have a less -than-significant impact. If
net new VMT exceeds the existing land use, apply
the thresholds described above.
No set threshold
Other
Development
Projects
City may apply adopted residential, office or retail
VMT thresholds to other development projects that
have predominant operating characteristics similar
to those uses. Alternately, City may use more
location-specific information to develop specific
thresholds for other land use types. In doing so,
analysis should consider the information described
in the CEQA Guidelines (Section 15064.7) on the
development of thresholds of significance.
No set threshold. Evaluated
on case-by-case basis based
on OPR guidance
Notes:
1. Quantitative thresholds will be updated as required with subsequent updates to the City Travel Demand Model
and/or per revisions to CEQA Guidelines or OPR Technical Advisory on VMT analysis.
Transportation Projects Exempt from VMT Analysis
Transportation projects that would not likely lead to a substantial or measurable increase in
vehicle travel can be presumed to have a less-than-significant transportation impact. Such
projects include, but are not limited to:
Road diets (reducing or narrowing vehicular travel lanes)
Installation of roundabouts or traffic signals
Roadway rehabilitation and maintenance
Safety improvements that do not substantially increase auto capacity
Installation or reconfiguration of la nes not for through traffic (addition of left/right turn
lanes, etc.)
Addition of roadway capacity on local and collector streets, providing the project also
substantially improves conditions for pedestrians, cyclists or transit
Timing of traffic signals
Removal of on-street parking
Addition or enhancement of pedestrian, bicycle and transit facilities and services
Projects that fall within the abovementioned categories can be considered exempt from
conducting a quantitative VMT analysis.
Transportation Projects Requiring VMT Analysis
Development- and City-initiated roadway capacity projects that involve infrastructure
improvements that may result in a measurable and substantial increase in vehicle travel, such as
the addition of through lanes on existing or new highways and arterial streets, should be scoped
for analysis of induced traffic demand. Where roadway capacity projects may result in increases
to vehicle travel, the estimated change in VMT should be quantified using the SLO TDM or other
approved analysis tools. No standard significance thresholds have been adopted for induced
traffic analysis; thus, potential impacts shall be evaluated on a case-by-case basis consistent
with CEQA Guidelines and applicable technical guidance while ensuring that the analysis
addresses:
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Direct, indirect and cumulative effects of the transportation project , including potential
for induced demand (CEQA Guidelines, § 15064, subds. (d), (h))
Near-term and long -term effects of the transportation project (CEQA Guidelines, §§
15063, subd. (a)(1), 15126.2, subd. (a))
The transportation project’s consistency with state greenhouse gas reduction goals
Pub. Resources Code, § 21099)34
The impact of the transportation project on the develop ment of multimodal
transportation networks (Pub. Resources Code, § 21099)
The impact of the transportation project on the development of a diversity of land uses
Pub. Resources Code, § 21099)
For transportation projects that have already been evaluated f or VMT at a programmatic level,
such as within a General Plan or Specific Plan EIR, project-level analysis may tier from that
programmatic analysis.
Traffic Safety & Access Management
Evaluation of the project’s effect(s) on traffic safety shall include:
1. An assessment of the project’s potential effect on each study intersection and segment s that
has been identified as a high-priority safety locations as part of the City Annual Traffic Safety
Program.
2. A preliminary geometric and sight distance assessment of the project and its frontage s
including access points, other existing & planned future driveways, and existing and planned
future intersections up and downstream of the project. Evaluate proposed site access and of f-
site circulation with the Access Management policies published in the Chapter 1010 of the City’s
Engineering Standards.
3. A queueing and functional area assessment of each study intersection.
Project impacts are considered significant if any of the following findings are made:
1. The project is projected to exacerbate an existing collision pattern at a high priority
safety location as identified in recent editions of the City’s Annual Traffic Safety Report
based on professional engineering judgement .
2. The project substantially increases hazards due to a geometric design features, such as
frontage or access improvements that include a ny features that are inconsistent with
applicable geometric design standards or that could obstruct adequate sight distance for
pedestrians, bicycles, buses, or automobiles.
3. The project’s proposed access point(s) are unrestricted and within the functional area of
an intersection or conflict with adjacent driveways within close proximity.
4. Project traffic extends, or exacerbates ext ension, of the functional area of study
intersections past existing driveways or into the functional area of other intersections.
5. Project traffic extends, or exacerbates extension, of queue lengths beyond turn pocket
storage length into thru travel lanes increasing the propensity for rear-end collisions.
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Instances where project traffic increase queue lengths by less than one car length (25’)
shall be considered insignificant.
It is important to note that for the purposes of CEQA analysis, queueing concerns that do not
result in a contextually significant hazards in terms of traffic safety should not be used as a proxy
for justifying increases in roadway capacity. Engineering judgement shall be practices to clearly
distinguish safety concerns from capacity-related queuing issues, which should not be used as
the basis for transportation mitigation under CEQA.
Consistency with Adopted Policy & Plan for CEQA Analysis
The project, its frontages, and any facilities constructed by the project shall be evaluated for
proposed implementation consistency with adopted
plans as well as project compatibility with future
transportation infrastructure contemplated in adopted
plans not to be constructed by the project.
The projec t and its traffic generation effect on
multimodal modal level of service, excluding
automobiles, shall be conducted for all scenarios.
Assessment of Consistency with General Plan Policy
shall include an assessment of the project’s impacts on
Pedestrian, Bicycle, and Transit Level of Service
standards as well as Neighborhood Traffic Management
standards.
Threshold of Significance:
Project impacts are considered significant if any of the
following findings are made:
The project proposes to implement transportation infrastructure inconsistent with adopted
plans, policies, or standards.
The proposed project impedes or constrains future planed transportation infrastructure ,
including planned enhancements to pedestrian, bicycle and transit facilities and services .
Project traffic or characteristics result in VMT increases that exceed City thresholds.
Project traffic added to neighborhood streets exceeds or exacerbates traffic volumes level
beyond adopted General Plan Thresholds.
Note that local policies that esta blish performance objectives based on measures of vehicle
congestion or delay shall not be used for the purposes of defining CEQA impacts.
V. MULTIMODAL TRAFFIC OPERATIONS ANALYSIS METHODS & POLICY
ASSESSMENT
The following section describes analysis methods and significance thresholds for evaluation of
transportation deficiencies based on local policy conformance. These analyses inform Part 2 of
Applicable Plan and Policies include:
1. SLO General Plan
2. Specific Plan
3. Bicycle Transportation Plan /
Active Transportation Plan
4. Short or Long Range Transit
Plan
Other plans that maybe applicable include
5. SLOCOG Regional
Transportation Plan
6. SLO County General Plan
7. Cal Poly Master Plan
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14TransportationImpactStudyGuidelines
the final Transportation Impact Study document: Multimodal Traffic Operations Analysis &
Policy Assessment. Findings of these analyses can be used to identify policy deficiencies, but
measures involving vehicle congestion or delay shall not be used to define impacts or guide
mitigation strategies for CEQA analysis.
Multimodal Level of Service and Capacity
All intersection and segment analysis shall be based upon the current version of the Highway
Capacity Manual (HCM), unless otherwise approved by the Transportation Manager. Analysis
periods should be confirmed by the Transportation Division in scoping the study . Existing a nd
Near Term (with and without Project) analysis scenarios should assume actual traffic signal
timing s unless otherwise directed. Cumulative analysis may assume optimized signal timings
using reasonable timing inputs consistent with traffic engineering standards and best practices.
Analysis models should be geometrically correct and include peak hour factors recorded with
the traffic counts.
Peak hour factors shall be applied for Existing and Near T erm analysis scenarios by intersection
approach only if using the same 15 -minute period to calculate the factor for each approach.
Otherwise, the average peak hour factor for the full intersection shall be applied to each
approach. A peak hour factor of 0.92 may be assumed for Cumulative analyses where supported
base on engineering judgement.
Analysis Software
The City uses a toolbox of software programs for conducting and reviewing traffic impact
studies. Unless otherwise approved, the most current version of following programs are to be
used:
TransCAD: City of San Luis Obispo Travel Demand Model (TDM) for all VMT analysis,
volume forecasting and trip distribution estimation.
Synchro / SimTraffic: Primary operational and micro -simulation model for intersec tion
analysis.
McTrans: Multimodal LOS analysis tool for street segments
SIDRA Intersection: Preferred analysis tool for roundabout control intersections
VISSIM: Secondary micro -simulation model for complex analyses or multi-modal
simulation.
In addition to the abovementioned software tools, roadway segment level of service and
capacity can be calculated manually or using other approved spreadsheet applications. It is the
responsibility of the consultant to ensure that models are properly calibrated and val idated for
the study area prior to use.
Automobiles
Signalized Intersections Level of service and delay at signalized intersections should be reported
for the overall intersection. The maximum Volume to Capacity ratio (V/C) for the overall
intersection sho uld be reported as well as for any deficient approaches or movements. Vehicle
queues should be reported for each lane or lane group with a dedicated turn pocket. Project-
related deficiencies are identified where:
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A. Project traffic causes minimum LOS standards to be exceeded or further degrade s
already exceeded LOS standards and the V/C ratio is increased by .01 or more.
B. Project causes or exacerbates 95th percentile turning movement queues exceeding
available turn pocket capacity by one car length (25’) or more and presents a
contextually significant safety hazard.
C. Project proposes roadway geometry changes that cause minimum LOS standards to be
exceeded or further degrades already exceeded LOS standards for the overa ll
intersection or individual lane groups.
Roundabout Intersections Level of service and delay at roundabouts should be reported for the
overall intersection and for each approach. Vehicle queues should be reported for each lane or
lane group. Project-related deficiencies are identified where:
A. Project traffic causes minimum LOS standards to be exceeded or further degrades
already exceeded LOS standards and the V/C ratio is increased by .01 or more.
B. Project causes or exacerbates 95th percentile turning movement queues to the point
where turn poc ket turn pocket capacities are exceeded by at least one car length (25’)
and presents a contextually significant safety hazard.
C. Project causes or exacerbates 95th percentile queues by at least one vehicle length (25’)
at an adjacent intersection to the po int where queues spill back into the roundabout
functional area.
D. Project proposes roadway geometry changes that minimum LOS standards to be
exceeded or further degrades already exceeded LOS standards.
Unsignalized Intersections Level of service for unsigna lized intersections should be reported for
minor street approaches as well as any major street turn movements. The maximum Volume to
Capacity ratio (V/C) for the overall intersection should be reported as well as any deficient
approaches or movements. If an unsignalized intersection exceeds minimum level of service
standards a signal warrant analysis shall also b e conducted. Project-related deficiencies are
identified where:
A. Project traffic causes minimum LOS standards to be exceeded OR further degrades
already exceeded LOS standards , and all of the following three conditions are met:
a. V/C ratio is increased by .01 or more; and
b. The project adds at least 10 trips to the critical approach/movement; and
c. The intersection satisfies a traf fic signal warrant analysis. It should be noted that
that satisfaction of signal warrants alone does not dictate that a traffic signal
would be the required solution to address operational deficiencies .
B. Project proposes roadway geometry changes that minimum LOS standards to be
exceeded or further degrades already exceeded LOS standards.
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Roadway Segments Level of service should be reported for scoped street segments utilizing
AADT-based Level of Service thresholds as adopted in the City general plan.
A. Project traffic causes minimum LOS standards for either direction to be exceeded , or
further degrades already exceeded LOS standards and the volume-to-capacity (v/c) ratio
increases by at least 0.01 with the Project.
B. Project proposes roadway geometry changes that minimum LOS standards to be
exceeded or further degrades already exceeded LOS standards.
Bicycles & Pedestrians
Bicycle and pedestrian level of service analysis should follow the methodologies established in
the current Highway Capacity Manual (HCM), unless alternate methodologies are approved by
the Transportation Manager. For the purposes of forecasting LOS calculations, pavement
condition rating should be assumed at 3.0 unless there are other overriding circumstances. It is
acknowledged that under certain high vehicle volume conditions , the HCM methodology for
bicycle and pedestrian level of service estimation can be insensitive to improvement measures,
therefore may not always be appropriate to define project-related deficiencies under these
circumstances. In cases where MMLOS results are non-intuitive or inappropriate, alternative
analysis techniques may be approved at the discretion of the Transportation Manager.
Intersections Bicycle & Pedestrian level of service analysis should be conducted at intersections
scoped in the traffic study. Pedestrian & Bicycle level of service score and grade should be
reported for each intersection approach or crosswalk. HCM intersection LOS analyses may not
be sensitive to operational characteristics of Class I multiuse paths at intersections. If a parallel
Class I path present, LOS shall be qualitatively assessed based on engineering judgement.
Project-related deficiencies are identified where:
A. Project traffic causes minimum LOS standards to be exceeded.
B. Project proposes modifications to roadway geometry that causes minimum LOS
standards to be exceeded or conflicts with engineering best practices for design of safe
intersection and driveway crossings.
C. Project-related traffic or geometric modifications further degrades already exceeded
LOS standards and there is contextual significance to the impact. Contextual sig nificance
may be evaluated qualitatively, and can generally be interpreted as a project-related
action that results in a negative change to the bicycle/pedestrian environment that is
likely to be noticeable to the average user. (i.e. a decrease in the effe ctive buffer width
between motor vehicle and bicyclists/pedestrians, addition of traffic adjacent to a
bicycle/pedestrian facility that would be noticeable during a typical walk/bike trip,
significant increases in crossing delays, etc.)
Segments Pedestria n level of service analysis should be conducted on public Collectors and
Arterials that front or are internal to the project , or where a project adds at least 20 peak hour
motor vehicle or person trips to the facility. Bicycle level of service should be co nducted on
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existing or planned bikeway routes, as adopted in the City’s Bicycle Transportation Plan/Active
Transportation Plan, that front or are internal to the project, or where a project adds at least 20
peak hour motor vehicle or person trips to the fa cility. At the discretion of the Transportation
Manager, bicycle segment analysis may be conducted using Bicycle Level of Traffic Stress (LTS) in
lieu of HCM level of service methodologies. Where LTS analysis is used, the following LTS-to-LOS
equivalencies shall be assumed for identifying operational deficiencies:
LOS A = LTS 1
LOS B/C = LTS 2
LOS D = LTS 3
LOS E/F = LTS 4
As with intersections, if a separate adjacent and parallel bike or pedestrian facility is present LOS
shall be assumed as follows:
LOS A (LTS 1) where Class I paths have a width of 12 feet or more, and are separated
from the adjacent motor vehicle traveled way by at least 10 feet or with a vertical
element, such as a railing or landscaping.
LOS B (LTS 2) where Class I paths have a width less than 12 feet, or are separated from
the adjacent motor vehicle traveled way by less than 10 feet with no vertical elements.
Project-related deficiencies are identifie d where:
A. Project traffic causes minimum LOS/LTS standards to be exceeded.
B. Project proposes modifications to roadway geometry that causes minimum LOS /LTS
standards to be exceeded or conflicts with engineering best practices for bicycle and
pedestrian facility design, including safety at intersection and driveway crossings .
C. Project-related traffic or geometric modifications further degrades already exceeded
LOS/LTS standards and there is contextual significance to the impact. Contextual
significance may be evaluated qualitatively , and can generally be interpreted as a
project-related action that results in a negative change to the bicycle/pedestrian
environment that is likely to be noticeable to the average user. (i.e. a decrease in the
effective buffer width between motor vehicle and bicyclists/pedestrians, addition of
traffic adjacent to a bicycle/pedestrian facility that would be noticeable during a typical
walk/bike trip, etc.)
Transit
Segments Transit level of service analysis should be conducted at segments scoped in the traffic
study that have current or planned transit service. Transit frequency, load factor, and LOS score
should be reported for transit routes servicing the project. A map should also be provided
depicting the project and servicing transit stops with 1/8- and ¼-mile mile bands around those
stops.
Project-related deficiencies are identified where:
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A. Project traffic causes minimum LOS standards to be exceeded or further degrades
already exceeded LOS standards and there is contextual significance to the deficiency.
B. Project proposes businesses or dwellings that are beyond 1/4 mile in existing developed
areas and/or beyond 1/8 mile of employment -intensive uses or medium to high density
residential uses in City expansion areas.
If approved by the Transportation Manager, a streamlined transit analysis may be performed in
lieu of detailed segment HCM LOS calculations. A streamlined analysis would include a summary
of existing transit load factors and evaluation of whether project -generated transit ridership
would cause load factors to exceed 0.83, or add ridership to routes where existing load factors
already exceed 0.83.
Neighborhood Traffic Analysis
Projects which include new local residential streets or have trips forecasted on local residential
street will typically be required to evaluate the impact of neighborhood traffic conditions.
Project impacts are considered significant if the maximum neighborhood ADT or speed
thresholds established in Table below, of the Circulation element, are exceeded or the project
adds traffic to a neighborhood already exceeding the ADT threshold.
Street Classification Maximum ADT Maximum Speed
Local Residential 1,500 25 mph
Residential Collector (Minor) 3,000 25 mph
Residential Collector (Major) 5,000 25 mph
A monitoring program shall be a standard condition of approval for all projects with a potentially
significant impact on neighborhood traffic conditions. Because it’s not feasible to estimate
speed impacts, follow-up monitoring programs will be the primary method for estimating
impacts on neighborhood speeds. Unless there are any documented events or conditions that
could affect observed baseline speeds it shall be assumed that any increase in neighborhood
speeds after the project is occupied is attributed to the project.
Modal Priorities
In addition to maintaining minimum levels of service, the City’s Circulation Element establishes
priorities for various modes such that construction, expansion, or improvements to one mode
should not degrade the level of service of a higher priority mode. Where i mprovements required
to offset project-related LOS deficiencies for one travel mode would result in the degradation of
a higher priority mode, that shall be considered a residual deficiency and should be addressed as
well.
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VI. ADDRESSING CEQA IMPACTS AND OPERATIONAL DEFICIENCIES FOR
LOCAL POLICY CONFORMANCE
Approach
Overall, CEQA mitigation measures and recommended improvements/actions to correct local
policy deficiencies caused by a project, should follow the City’s Circulation Element Goals &
Objectives of supporting environmentally sound technological advancement, supporting a shift
in modes of transportation, and establishing beautiful & livable street corridors. For example if a
project creates a level of service deficiency at an intersection or roadway, measures that would
reduce vehicle demand generated by the project, such as enhanced bike and pedestrian
facilities or improved transit service, should be considered before measures that would increase
vehicle capacity. Similarly, mitigations recommended to address VMT impacts should support
existing City plans and policies to reduce dependence on single -occupant motor vehicle use,
such as improving transit service consistent with the Short -Range Transit Plan or constructing
bicycle facilities consistent with the Ci ty’s adopted Bicycle Transportation Plan/Active
Transportation Plan.
CEQA Mitigation Strategies for VMT Impacts
When significant VMT impacts are identified as part of the traffic impact analysis , mitigation
measures shall be included to address those impa cts. The impact study should establish the
legal nexus between the project and the mitigation measures. Per current CEQA Guidelines and
OPR technical guidance, potential strategies for addressing project VMT impacts include, but are
not limited to:
Implementation of a Transportation Demand Management Program (TDM).
Improve or increase access to transit.
Incorporate a mix of land uses to increase access to common goods and services, such
as groceries, neighborhood retail, schools and childcare services.
Loca te project in lower-VMT areas of the City.
Improve or increase access to active transportation facilities within the project vicinity,
or construct planned active transportation in other areas of the City that improve cross -
town mobility and safety for act ive transportation users.
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Provide car-sharing, bike-sharing, ride-sharing, neighborhood electric vehicle charging
stations, or other on-site amenities to increase access and use of greenhouse gas
reducing transportation modes.
The traffic study’s description of each mitigation measure should include the following:
1. Figure schematically depicting location and nature of each mitigation measure and
description of implementation feasibility (i.e . right-of-way requirements,
constructability, etc.).
2. Quantitative estimate of anticipated VMT reduction and supporting summary
documenting the tools and methodology used to develop this estimate. Where feasible,
the same tool used to establish the City’s VMT thresholds and for project -level VMT
analysis (i.e. SLO TDM) shall be used to quantify VMT reductions with mitigation.
3. Comparison table of VMT with and without mitigation.
4. If scoped, provide a planning -level cost estimate of each mitigation measure,
timing/phasing of measures, and equitable share calculat ions.
Strategies for Addressing Local Policy Deficiencies
When a proposed project is anticipated to create or exacerbate deficiencies related to local
policy objectives, such as instances where minimum MMLOS standards are exceeded,
improvements and/or actions shall be recommended to offset these deficiencies and inform
development of project conditions of approval. The study should establish a legal nexus
between the project and recommended strategies and include the following:
1. Figure schematically depicting location and nature of each improvement/action and
description of implementation feasibility (i.e. right-of-way requirements,
constructability, etc.).
2. Comparison table(s) showing deficient study locations with and without recommended
improvements.
3. If sco ped, provide a planning -level cost estimate of each improvement
recommendation, timing/phasing of actions, and equitable share calculations.
Intersection Control Type Selection
Circulation Element policies 7.0.2 Street Network and 9.1.6 Streetscapes & Major Roadways
establish roundabouts as the City’s preferred intersection control type where feasible. Per these
policies, roundabout control should be the first and preferred improvement strategy where
right-of-way issues, environmental factors, or other design constraints allow.
When roundabout control is infeasible, consideration and evaluation of multi -way stop control
or signalized control should utilize the California MUTCD’s Multi -Way Stop and Traffic Signal
warrants. Detailed consideration should be given when determining the applicability of
individual warrants.
For example, the MUTCD chapter on Peak Hour Signal Warrant s states “This warrant shall only
be applied in unusual cases, such as office complexes, manufacturing plans, industrial complexes,
or high-occupancy vehicle facilities that attract or discharge large numbers of vehicles over a
short time”. The peak hour warrant should only be used when the volume in a peak hour
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exceeds 45% or more of the 24 -hr volume and should not replace the need for a more
comprehensive engineering study when confirming the need for signalization.
Transit Deficiencies
Transit operations are typically dynamic, can change over time given funding and policy
circumstances, and are largely outside the control of individual private projects. Potential
strategies to address project-related transit operations deficiencies include, but are not limited
to:
Fair share financial contribution towards expanding the transit fleet, which allows for
future service improvements
Construction of new transit stops, or upgrades to benches, shelters or other amenities
at existing transit stops.
Installation or fair share financial contribution towards transportation system
improvements that improve transit operations, such as equipment for transit signal
priority or queue jumps at congested intersections.
Bicycle and Pedestrian Deficiencies
Potential strategies to address project-related bicycle and pedestrian safety and LOS deficiencies
include, but are not limited to:
Installation of sidewalks where none currently exist
Installation of facilities physically-separated from motor vehicle traffic, such as Class I
multi-use path) or Class IV (cycle track) bikeways.
Addition of elements that further buffer pedestrian facilities from motor vehicle traffic,
such as installation of street trees and/or landscaped parkways.
Traffic calming or other improvements that reduce motor vehicle speeds adjacent to
bicycle and pedestrian facilities.
Major intersection crossing upgrades, such as construction of roundabouts, protected
bicycle intersections, or pedestrian hybrid beacons (PH B).
Minor intersection crossing upgrades, such as addition of lead crossing signal intervals,
dedicated bicycle or pedestrian “scramble” signal phases, bike boxes, curb extensions
bulbouts), median refuge islands or rapid rectangular flashing beacons (RR FBs).
Addition of signage and/or striping modifications that impro ve safety at conflict points
with motor vehicles.
Equitable Share Responsibility
For level of service and capacity deficiencies, equitable share responsibility for improvements
shall be calculated based upon the percent of project trips forecasted on the impacted facility
for the corresponding analysis and time period. In cases where the impact is primarily attributed
to a specific component of the facility, such as a left turn lane, it may be more appropriate to
calculate the percent of project trips forecasted on the specific impacted component of the
facility as opposed to the whole facility.
Equitable share calculations are not applicable to safety and neighborhood impacts. Also , i n
circumstances where the project is receiving substantial benefit from the identified mitigation
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measure and that measure would not have otherwise been considered if the project was not
proposed, the project should take full share responsibility. Examples of the se types of
circumstances include but are not limited to.
A new access point for a project where upgraded control and/or associated striping at
that intersection is an identified mitigation measure.
A mitigation measure is identified within a generally bui lt out area where there are no
planned transportation improvements.
Appendix A:
VMT Screening Maps
City of San LuisObispoResidentialVMTScreening Map
Residential VMT Per Capita
CityLimit
85% of Average VMT
85% - 100% of Average VMT
100% - 115% of Average VMT
115% of Average VMT
Regional Average = 16.7685% of Regional Average (Impact Threshold) = 14.25
Too Little Data - Further Analysis Needed
Data Source: City of San Luis Obispo Travel Demand Model
Last Updated: 6/1/2020
0 2,500 5,0001,250
Feet
City of San LuisObispoWorkVMTScreeningMap ±
0 2,500 5,0001,250
Feet
Work VMT Per Employee
CityLimit
85% of Average VMT
85% - 100% of Average VMT
100% - 115% of Average VMT
115% - 130% of Average VMT
Regional Average = 14.6585% of Regional Average (Impact Threshold) = 12.45
Too Little Data - Further Analysis Needed
Data Source: City of San Luis Obispo Travel Demand Model
Last Updated: 6/1/2020
130% of Average VMT
Appendix B:
SLO TDM Technical Guide Calculating
VMT Cambridge Systematics)
February 27, 2020 www.camsys.com
City of San Luis Obispo Travel Demand Model
Technical Guidance
Calculating VMT
prepared for
City of San Luis Obispo
prepared by
Cambridge Systematics, Inc.
Draft Guide
draft guide
City of San Luis Obispo Travel
Demand Model Technical Guidance
Calculating VMT
prepared for
City of San Luis Obispo
prepared by
Cambridge Systematics, Inc.
1801 Broadway, Suite 1100
Denver, CO 80202
date
February 27, 2020
SLO TDM Technical Guidance
Cambridge Systematics, Inc.
i
Table of Contents
1.0 Introduction ........................................................................................................................................ 1-1
2.0 VMT Required Files ............................................................................................................................ 2-1
3.0 VMT Calculation Procedure .............................................................................................................. 3-1
3.1 Create Empty Matrix Files for Calculations................................................................................ 3-1
3.2 Sum Vehicle Trips ...................................................................................................................... 3-3
3.3 Calculate VMT by Zone Pair ...................................................................................................... 3-5
3.4 Summarize Total VMT for One or More Zones ......................................................................... 3-7
4.0 Employment Calculation ................................................................................................................. 4-11
4.1 Determine Total baseline employment .................................................................................... 4-11
4.2 Distributing Employment to TAZ .............................................................................................. 4-11
4.3 Project Level Employment ....................................................................................................... 4-11
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1.0 Introduction
This document provides a brief technical description of how to calculate VMT generated by one or more
zones using SLO Model outputs and the TransCAD menu system.
Note that this guide includes a simplification to make the calculations straightforward. The VMT tool uses
distance skims for the peak (AM and PM) and off-peak (MD and NT) periods. This guide makes a
simplification and uses peak skims to define trip length.
This guide provides instructions on computing home-based VMT and on computing total non-residential
VMT. Similar concepts can also be used to compute commute VMT by summarizing home-based work
HBW) attractions (HBW matrix column sums).
The SLO Model utilizes a land use-based model to compute trip attractions. For this reason, TAZ-level and
even city-level employment is not a direct input to this model. This guide also provides guidance on
calculating employment at the TAZ level based on model outputs.
2.0 VMT Required Files
Only a subset of model outputs are required to perform VMT calculations. This set of files is listed in the
table below.
Files required for VMT Calculations
File Name Notes / Description
ModeTrip\Trip_[PURP]_ [PK/OP].mtx These files contain production/attraction vehicle
trips output from mode choice.
Skim\skim_pk.mtx This file contains the peak period drive alone
shortest paths. Note: off-peak skims are
available as well, but not used in this guide.
TripGen\SocioBV.bin This file contains socioeconomic data totals,
including total population and employment.
SLO_TAZ.dbd This geographic file contains the TAZ definitions.
3.0 VMT Calculation Procedure
This step will produce a pair of matrix files. The first will include all home-based vehicle trips in production to
attraction format. The second will include all trips in production to attraction format, including non-home-
based trips.
3.1 Create Empty Matrix Files for Calculations
This step will create a pair of empty matrix files that can be used to perform calculations.
1. Open a trip table
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a. This guide uses Trip_HBO_pk.mtx, but any trip table will work.
2. Choose Matrix Copy from the TransCAD Menu
3. Select only the DA matrix core
4. Save the matrix in a convenient location
a. Save the copy in a new folder named Analysis within the model run folder.
b. Use the filename HB_VMT_Analysis.mtx.
c. Change the matrix label to Home-Based VMT Analysis when saving the file.
5. Close all files, then re-open the newly created matrix. This will help prevent accidental changes to the
original file.
6. From Matrix > Contents, add two new cores to the matrix.
7. Rename the three matrix cores to “Trips” “Length (Skim)” and “VMT”. This can be done from Matrix
Contents.
8. Clear the first matrix core in the home-based trip matrix. This can be done from Matrix Fill.
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9. Make a copy of the home-based analysis file.
a. Name the copy AllTrip_VMT_Analysis.mtx.
b. Change the matrix label to All Trip VMT Analysis.
3.2 Sum Vehicle Trips
This step will populate the Trips matrices for both home-based and all trips.
1. Close all files to start with a clean workspace
2. Open the Trip_[PURP]_ [PK/OP].mtx files for home-based purposes only. This can be done by
selecting all of the relevant files from the TransCAD File Open dialog.
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3. Open the recently created HB_VMT_Analysis.mtx file.
4. Fill the HB_VMT_Analysis matrix with the total home-based vehicle trips
a. Make sure that the Trips matrix is active and that the HB_VMT_Analysis.mtx window is active.
b. Choose Matrix Fill ( ) from the TransCAD menu or toolbar.
c. Select the Formula tab.
d. Click the Sum Matrices ( ) button.
e. Select the matrices for [DA], [SR2] and [SR3] and add them to the Selected Cores list, then click
OK.
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f. Select the Treat missing values as zeros checkbox, then click OK to generate a formula.
g. Click OK again to populate the Trips matrix core with the sum of all home-based vehicle trips.
5. Close all files, then use a similar procedure to fill the AllTrips_VMT_Analysis.mtx file with all trips.
a. This can be accomplished by repeating the steps above, but also including the WBO and OBO trip
matrices when opening the summary matrix files.
3.3 Calculate VMT by Zone Pair
1. Close all files to start with a clean workspace
2. Open the HB_VMT_Analysis.mtx file and the skim_pk.mtx file.
3. For convenience, populate the [Length (Skim)] core in the HB_VMT_Analysis.mtx file with the
corresponding matrix core in the skim_pk.mtx file.
a. Select the Length (Skim) core in the matrix.
b. Use Matrix Fill and the Formula tab as shown below. The source matrix can be selected from
the Matrix List.
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c. Close the skim matrix when done
4. Compute VMT by multiplying trips by length.
a. Select the VMT core in the matrix.
b. Use Matrix Fill and the Formula tab as shown below.
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5. Repeat the steps above using the AllTrips_VMT_Analysis.mtx file instead of the home-based file.
3.4 Summarize Total VMT for One or More Zones
1. Open the TAZ Layer in TransCAD (e.g., SLO_TAZ.dbd). It may be best to work with a copy, since this
process will modify the file, and a mistake could overwrite important data.
2. Add fields to the TAZ dataview, setting field types to Real (8 bytes):
a. ResVMT to hold Residential VMT
b. NonResVMT to hold non-residential VMT
3. Populate the Residential VMT field.
a. Open the HB_VMT_Analysis.mtx file.
b. Select Matrix Fill Dataview ( ) from the TransCAD menu or toolbar.
c. Fill the ResVMT field with the VMT Row Sum.
d. Close the HB_VMT_Analysis.mtx file.
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4. Populate the Non-Residential VMT field
a. Open the AllTrip_VMT_Analysis.mtx file.
b. Select Matrix Fill Dataview ( ) from the TransCAD menu or toolbar.
c. Fill the NonResVMT field with the VMT Column Sum.
Close the AllTrip_VMT_Analysis.mtx file.
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5. Summarize VMT, population, and employment for a set of zones
a. Open the SocioBV.bin file.
b. Join the socioeconomic data view to the TAZ layer.
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c. Select zones to summarize either by pointing or using a selection query (Selection Select by
Condition or ).
d. Activate the joined view and show only the selected records.
e. Choose Dataview Summary Statistics ( ) from the TransCAD menu or toolbar.
f. Obtain residential VMT (Res_VMT), non-residential VMT (NonRes_VMT), population (HH_POP),
from the summary dataview.
6. Calculate residential VMT per capita
a. Calculate residential VMT per capita as Res_VMT / HH_POP from the summary view.
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4.0 Employment Calculation
The SLO Model uses land use inputs in terms of development square footage, not based on employees,
which is required to compute VMT per employee. To calculate commute VMT per employee, it is necessary
to determine the number of employees at the TAZ level. This can be done using the procedure described
below.
4.1 Determine Total baseline employment
The first step is to determine the total employment within either the City or SOI. This example will consider
City employment. Application for the SOI is similar, but it is important to properly account for employment at
CalPoly when determining employment for the SOI as a whole.
At the time of writing, total employment for the City is assumed to be 42,794.
4.2 Distributing Employment to TAZ
The model can be assumed to produce a consistent number of home-based work attractions per employee
at each non-residential location. The number of employees in each TAZ can be calculated using the
equations shown below.
Conversion Factor] = [Total City Employment] / [Total City HBW Attractions]
TAZ Employment] = [Conversion Factor] * [TAZ HBW Attractions]
The necessary information can be obtained from the following locations:
Total City Employment: External input described in Section 4.1.
Total City HBW Attractions: Row Sum of the file HBW_A column in the model output file
ZonePABalanced.bin.
TAZ HBW Attractions: Value in the HBW_A column for the selected TAZ in the model output file
ZonePABalanced.bin.
4.3 Project Level Employment
In model application, it may be necessary to add a new land use to the model and calculate the resulting
commute VMT per new employee. This requires computing employment for a specific project. Due to the
nature of trip balancing, new employment cannot be determined by simply subtracting total HBW attractions
in no-project model from a project model run. Instead, HBW attractions must be converted to employment at
the TAZ level.
One way to approach this is to isolate a new development in a single TAZ. Alternately, TAZ-level
employment with and without project can be computed and subtracted to arrive at project employment. TAZ
level employment can be computed using the process described in Section 4.2. When performing this
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calculation, the [Conversion Factor] should be based on the no-project model even when computing project
level employment.