Congestion Dashboard

Regional Trends


Travel Time Index (TTI), defined as the ratio of actual travel time to free-flow travel time, measures the intensity of congestion. The higher the index, the more congested traffic conditions it represents, e.g., TTI = 1.00 means free flow conditions, while TTI = 1.30 indicates the actual travel time is 30% longer than the free-flow travel time.

Planning Time Index (PTI), defined as the ratio of 95th percentile travel time to free flow travel time, measures travel time reliability. The higher the index, the less reliable traffic conditions it represents, e.g., PTI = 1.30 means a traveler has to budget 30% longer than the uncongested travel time to arrive on time 95% of the times (i.e., 19 out of 20 trips), while TTI = 1.60 indicates that one has to budget 60% longer than the uncongested travel time to arrive on time most of the times.


Inspired by various agency and jurisdictional dashboard efforts around the country (e.g., the Virginia Department of Transportation Dashboard), driven by the MAP-21 legislation and the emerging probe-based traffic speed data from the I-95 Corridor Coalition Vehicle Probe Project, this quarterly updated National Capital Region Congestion Report takes advantage of the availability of rich data and analytical tools to produce customized, easy-to-communicate, and quarterly updated traffic congestion and travel time reliability performance measures for the Transportation Planning Board (TPB) Planning Area. The goal of this effort is to summarize the region's congestion and the programs of the TPB and its member jurisdictions that would have an impact on congestion, to examine reliability and non-recurring congestion for recent incidents/occurrences, in association with relevant congestion management strategies, and to prepare for the MAP-21 performance reporting. For more information and technical details, please see the full report.

News & Multimedia

Results: 35 found.
  • Thanksgiving2016_flickr-Bossi_cropped2

    Pre-Thanksgiving traffic slowdowns reached their worst point Tuesday evening

    December 1, 2016

    TPB traffic researchers looked at how traffic conditions on area roadways played out in the days leading up to Thanksgiving Day. Their analysis points to the...

  • SeptShock2016_flickr_Bossi_600

    Get ready for traffic to pick back up as part of "September Shock"

    August 30, 2016

    Next week marks the beginning of what area traffic experts have dubbed “September Shock,” the month-long phenomenon in which traffic delays on the region’s...

  • News

    Analysis Quantifies Drop in Roadway Congestion During Recent Papal Visit

    October 21, 2015

    A Transportation Planning Board analysis has quantified the traffic effects of Pope Francis' recent visit to the Washington region. The analysis, which showed...

  • Isiah Leggett

    County Executives Call for Greater Cooperation to Strengthen Regional Economy

    June 11, 2015

    Greater cooperation across borders on a variety of issues will be critical to the National Capital Region’s future economic success according to Prince George’s...

  • News

    Memorial Day Holiday Traffic Expected to Peak on Thursday, Not Friday

    May 19, 2015

    Traffic on Washington area highways ahead of the upcoming Memorial Day holiday weekend is expected to reach its worst point on Thursday afternoon, running...

  • News

    Researchers Identify Busiest Times, Roadways for Thanksgiving-Week Drivers

    November 18, 2014

    Using newly available, minute-by-minute traffic information from one recent Thanksgiving, researchers at the Transportation Planning Board have identified the...

  • News

    On Current Funding Trajectory, Metro Crowding and Reliability to Worsen

    January 14, 2014

    Barring any major changes to current funding trajectories, the region’s Metrorail system will face more crowding and less reliability in coming years, which...

Results: 35 found.