At its July meeting, the TPB will be setting the final set of performance targets the board will adopt before Visualize 2045. These two targets for highway infrastructure and system performance will help provide the region with a starting point to assess future performance.
About Performance Based Planning and Programming
The two most recent surface transportation laws, MAP-21 and the FAST Act, included provisions requiring the US Department of Transportation (USDOT) to create new rules for state departments of transportation (DOTs) and metropolitan planning organizations (MPOs) to collect data and set targets to support performance-based decision making. These targets are to be attainable, data driven, and realistic.
Since last year, TPB staff have been collaborating with the District of Columbia, Maryland, and Virginia departments of transportation. Together they have been analyzing, forecasting, and establishing performance targets in the areas of safety, maintenance, and system performance.
Having already set highway safety targets at the start of this year, the TPB is now finishing the analysis on several topics everyone can relate to, the condition of our bridges and pavement, and the reliability of the highway systems. For this set of performance targets, the TPB is creating its own quantifiable four-year targets based on information for the region. The region’s DOTs established statewide targets to meet a May 20 deadline. The TPB now has up to 180 days to set regional targets.
Pavement and Bridge Condition
The pavement performance measure applies to both interstate and non-interstate roadways within the TPB planning area. The measure is straightforward with an assessment of the percent of pavement that is in good condition and in bad condition. The Highway Performance Monitoring System (HPMS) field manual which considers the roadways’ roughness, cracking, rutting, and faulting, determines the metrics to assess the condition of the pavement.
The bridge performance measure only applies to the deck area (the portion used by vehicles and cyclists). The National Bridge Inventory (NBI) determines these criteria of structure length, deck width, or approach roadway width. As with the pavement performance measure the assessment is the percent of bridge deck area that is in good condition and in poor condition. The NBI condition ratings classify the bridge deck area which establishes the level of condition.
To arrive at targets for these two performance measures, TPB staff relied on the established state pavement and bridge targets. The statewide targets included construction projects that are anticipated in the next few years and future budget appropriations. With those, TPB staff calculated the total lane miles and the total bridge deck surface area for each state’s portion located within the TPB planning area. Next, TPB staff applied the statewide targets to the respective lane mileage and deck area within the TPB planning area, producing four-year targets. TPB staff expects that future performance will be close to the targets being set now.
Travel Time Reliability (TTR) and Truck Travel Time Reliability (TTTR)
Travel Time Reliability (TTR) and Truck Travel Time Reliability (TTTR) performance assess the reliability of the system performance of both the National Highway System (NHS) and Interstate System.
TTR is defined as the percent of person-miles on the interstate and non-interstate National Highway System roadways that are reliable. TTTR deals with freight movement on the Interstate System. Rather than a percentage, it is measured on the TTTR Index, the lower the number the more reliable truck travel is considered.
Both measures relied on the analysis of data from the National Performance Management Research Data Set (NPMRDS) collected by TPB staff. This resource serves as the baseline dataset needed for these newly established congestion and freight related performance measures. The NPMRDS, updated monthly, holds archival average travel times. 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, which, captured from smart phones and other sources of information, accurately illustrates travel speeds and delays over time. This is the first time this data will be used to measure travel and traffic congestion.
When developing future year targets for these two performance measures, 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 forecasts of 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 expects that future performance will be close to the targets being set now.
At its July meeting the TPB will consider approving the targets for highway infrastructure and highway system performance. This will mark the final set of performance measure targets set by the TPB and they will serve as a starting point for assessing future performance. The main goal of this new data-driven process is to instill a culture of performance-based decision-making and better efficiency of resources. TPB staff will prepare reports as part of Visualize 2045, the region’s new long-range transportation plan. Performance-based planning and programming requirements will lead to a stronger linkage between funded projects and how the region’s transportation system performs.
Matthew Gaskin is a TPB Transportation Planner