Overview of Vehicle Miles Traveled (VMT) Measures For Prince George’s County Climate Action Commission, May 2021 How local governments can use VMT metrics ●
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Transportation impact studies for development projects (focus of this memo) o
These studies are prepared by developers for projects of a certain minimum size.
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The studies identify current conditions at the site and its vicinity (roadway, pedestrian, bicycle, transit, freight) and future conditions with the new development.
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Based on the study, County staff identify needed improvements to serve the development and address added demand to the vicinity transportation network. In some cases, the County and developer identify alternative mitigation measures or modifications to the development plans.
General performance measures – jurisdictionwide or small areas o
Countywide metric related to emissions, livability, auto-dependence, availability of other transportation options.
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Used by Prince George’s County as one of the “Indicators of Success” in evaluating implementation of PLAN 2035
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Some states and localities are setting targets for VMT reduction in climate action plans and transportation plans 1 – and use other metrics like travel time, job accessibility, mode share.
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See CSG memo “Recommended Transportation & Land Use GHG Mitigation Strategies” and our climatetransportation report for more information.
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Within Prince George’s County, there are significant differences in how much households need to drive, even inside the Beltway (“Developed Tier”) part of the County.
Average VMT per Household Source: H+T Affordability Index, accessed May 2021.
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to VMT, jurisdictions use indicators of mobility and equity of the transportation system, such as travel time, job accessibility, safety, mode share, proximity to transit, etc.
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Advantages of VMT for use in Transportation Impact Studies ●
Measuring estimated VMT generated by a new development assesses the overall impact on the transportation system and climate emissions – VMT factors in car trip distances on the road network rather than just localized effects of each trip.
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See this clear 3-minute video on the change to VMT from relying heavily on Level of Service (LOS) measures by the city of Los Angeles.
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Traditional LOS measures, without other measures, can inadvertently penalize development in compact walkable areas with shorter driving distances.
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Measuring VMT can inform the jurisdiction about overall VMT-reducing potential for some types of development that could otherwise be disincentivized by other metrics.
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A number of jurisdictions in California use both LOS and VMT to inform impact analyses.
What Prince George’s County Currently Uses ●
Transportation Review Guidelines (2012), Prince George’s County Department of Planning
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Assesses localized impacts of trips generated by new development on road, pedestrian, bicycle and transit facilities. Also looks at facilities needed to serve the new development.
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Level of Service (LOS) for vehicle traffic at roadway intersections and segments.
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Uses County Tiers (Developed, Developing, Rural) for roadway LOS thresholds. Moderately more tolerance of congestion in Developed Tier (inside the Beltway).
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Transit-Oriented Development projects in designated Centers and Corridors credited with less car traffic generation if they meet guidelines for walkability (e.g., Intersection Density), density, and mix of uses. See excerpt below.
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Specific levels of pedestrian and bicycle facilities and accommodations are required in Centers and Corridors (part 2 of the Guidelines).
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The County’s updated subdivision regulations establish two new LOS categories for the zones that are Transit Oriented. These new LOS categories permit higher thresholds for installing new roadway infrastructure.
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Thus, current County Transportation Review Guidelines differentiate among certain types of locations at a very broad level (tier, centers/corridors, TOD zoning districts). However, other factors also affect resulting VMT and transportation impacts beyond the immediate vicinity of new development that are not captured in LOS metrics.
Source: Excerpt from Prince George’s County Transportation Review Guidelines, Part 1, Section 4, 2012.
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How measured, what developments ●
Exempted developments: small developments, those in low-VMT areas (e.g., near frequent transit, job centers, activity centers, walkable areas), or exemptions for special uses like affordable housing.
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Local governments typically have VMT calculator tool calibrated for local conditions that proposed developments use.
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Larger developments use the local jurisdiction or regional travel model (often required in traditional traffic studies).
Typical types of mitigation measures for new development ●
Impact threshold typically set based on regional or local jurisdiction average per capita VMT for residential development or average per job VMT for commercial uses.
San José, CA VMT Map for Residential Development Notes: - Green areas do not require VMT analysis – are below 15% of City average VMT - Yellow and Orange areas require VMT analysis - Red areas major new development projects not allowed except certain special uses (note: some of these areas have other conditions (e.g., low-lying) that already limit new development) - Exemptions, special conditions provided for certain industrial projects
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Mitigation measures – example below from large fast-growing California county with range of suburban and rural areas:
Source: Placer County, CA Transportation Study Guidelines, November 2020
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How this is typically implemented at the local level (e.g., subdivision, zoning ordinances, traffic impact study guidelines, any state coordination needed, etc.) ●
Transportation Review Guidelines (2012), Prince George’s County Department of Planning o
Update based on the Approved Countywide Master Plan of Transportation in 2009
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County will be updating its Master Plan of Transportation beginning Fall 2021
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Coordination with Zoning Ordinance and Subdivision Regulations
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County will begin process of updating its Master Plan of Transportation later this year
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Implementation challenges of VMT metrics for Transportation Impact Studies o
Requires original research by the jurisdiction to understand its local VMT patterns
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Based on averages of typical uses; may require other tools for proposed special uses
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More applicable to larger developments
Alternative Metrics ●
Total number of parking spaces provided by a new development is used by some cities to quantify mitigation needed for new car trips and VMT.
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Some jurisdictions waive LOS standards in dense urban areas and focus on multimodal demand and access.
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For an overview of new approaches see Modernizing Mitigation: A Demand Centered Approach (2018) by the State Smart Transportation Initiative and the Mayors Innovation Project for an overview on the topic.
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Walkability metrics like intersection density are used in development design and also in comprehensive planning to prioritize areas for new development and improved local policies and infrastructure. Example: Chicago regional planning maps and methodology.
Examples of places that use this, looking into it ●
California Senate Bill 743 – overview and in-depth resources and implementation assistance have been provided by the firm Fehr & Peers.
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Some places outside of California looking into using VMT or similar measures in Transportation Impact Analysis of new development: o o o
Minneapolis, MN City of Cambridge, MA Fairfax County, VA
Local experts for more information on VMT, new Transportation Impact Study Metrics: Mr. Kwasi Donkor Prince George’s County resident DC Office Director, Fehr & Peers transportation consultants K.Donkor@fehrandpeers.com 202.854.2737
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