How the region will measure performance for congestion management and emissions reduction


This post has been updated to include the draft targets the TPB will be considering for approval at the June meeting.

In June, the TPB will be setting targets for the region’s traffic congestion and emissions. They will provide starting points to assess progress going forward. (Bossi/Flickr)

Each year, the US Department of Transportation (USDOT) distributes funds to the states specifically for funding projects that address interrelated congestion and environmental issues, known as the Congestion Management and Air Quality, or CMAQ, program.

CMAQ funding is used for a range of projects, from buying cleaner transit buses to ride-sharing campaigns to building bike lanes. CMAQ projects are reported in a public access system (PAS) database by our region’s state departments of transportation: the District of Columbia DOT (DDOT), Maryland DOT (MDOT), and Virginia DOT (VDOT). Besides implementing these projects, DDOT and MDOT also choose the CMAQ projects for this region, while VDOT works with the local jurisdictions through their role in the Northern Virginia Transportation Authority to identify projects for that part of the region.

As part of the most recent federal surface transportation law, known as the FAST Act, performance-based planning and programming provisions required USDOT to craft new rules. These rules mean state departments of transportation and metropolitan planning organizations (MPOs) must collect data and set targets for three performance measures tied to the CMAQ program to support performance-based decision-making.

RELATED: New federal performance rules for MPOs, explained

In June, the TPB, as the MPO for the region, is expected to adopt an initial set of performance targets for traffic congestion and emissions reduction for the two-year period 2018-2019 and the four-year period 2018 to 2021. The region’s DOTs will act first, adopting targets to meet a May 20 deadline. MPOs then have up to 180 days to set targets. In the case of the traffic congestion targets, however, these must be the same targets. TPB staff have been closely coordinating with state DOT colleagues to reach agreement on a process for setting the same targets.

Measuring traffic congestion

Two performance measures are being used to assess traffic congestion. Both measures apply to the Washington, DC urbanized area, as defined by the U. S. Census Bureau. The first measure, peak hours of excessive delay, is the cumulative hours of excessive delay (travel time less than 20 miles per hour or 60% of the posted speed limit) experienced per person during peak periods for the year.

The second measure, the mode share of non-Single Occupancy Vehicles (non-SOV), is a measure of all trips being taken by carpool, van, public transportation, commuter rail, walking, or bicycling as well as telecommuting.

Data for the peak hours excessive delay measure is coming from a national database, the National Performance Management Research Data Set (NPMRDS). The NPMRDS is a monthly archive of average travel times, reported every 5 minutes when data is available, across the National Highway System. The travel times are based on vehicle probe-based data and assembled into an archive of speed and travel time data with associated location referencing information, that was collected from smart phones and other sources of information to accurately capture travel speeds and delays over time. This is the first time the region has used some of this recently available data to measure travel and traffic congestion.

The data for non-SOV travel comes from the U.S. Census Bureau. The American Community Survey collects representative data from the population, and in this case the performance measure uses commuting (journey to work) data from the survey.

To arrive at targets for these two performance measures for the next four years, TPB staff considered several methods, and arrived at a mathematical combination of information from two sources: first, using extrapolated trends of the past four years’ worth of data, and second, applying rates derived from the TPB’s travel demand model (which incorporates data on population and employment changes as well as transportation projects that will be opening, such as the Silver Line phase two extension to Dulles Airport and into Loudoun County). By averaging the trends in the recent actual performance and the long-term trends reflected by the travel demand model, TPB staff anticipates that future performance will be close to the targets being set now.

Measuring emissions reduction

The TPB will also approve a target for the performance measure for CMAQ emissions reductions, which applies to the Washington, DC area as this region is considered in non-attainment for ozone. For this region, ozone precursors volatile organic compounds (VOC) and nitrogen oxides (NOx) are the only emissions for which the region needs to report in the CMAQ emissions reduction performance measure.

The data for the performance measure comes from emissions reductions reported for projects in the CMAQ Public Access System. These emissions reductions are estimates arrived at during the CMAQ project planning process. There is no requirement that these estimates be calculated however, so some projects funded in this region do not have calculated emissions reductions.

To arrive at targets for the future, the three state DOTs developed projections of anticipated CMAQ projects programmed over the next four years to be built or implemented in this region. The emission reduction targets were then arrived at by adding the DDOT, MDOT, and VDOT projections together.

The above charts display draft targets for emissions and congestion for the region. At its June meeting, the TPB will be considering these targets for approval. (TPB)

What happens next?

At its June meeting the TPB will consider approving targets to be set as the region’s traffic congestion and emission reductions targets. These targets will provide a starting point to assess performance going forward. These targets will be revisited in 2020 and every other year thereafter for data-driven and performance-based decision-making.

In the next months, the TPB will be setting targets for performance measures in the areas of highway system performance and highway pavement and bridge condition. A report will be prepared as part of the Visualize 2045 long range plan for submission to the federal highway administration and federal transit administration. Performance-based planning and programming requirements will lead to a stronger linkage between funded projects and how the region’s transportation system performs.

TPB Engineer Eric Randall contributed to this article.

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