Roadway Clearance Time (RCT)

Roadway Clearance Time Definition

Of the 40 metropolitan areas participating in the Performance Metrics Adoption Campaign, 22 were collecting data to measure RCT. Of these 22 areas, 20 (91 percent) reported using a definition for RCT that was consistent with FHWA’s definition of RCT. In most cases, the collection of data to calculate RCT was motivated by a program, agency, or multi-agency policy for quick clearance—typically called an “Open Roads” program. An Open Roads program consists of legislation, policies and guidelines, and a range of services that enable a jurisdiction or operating agency to carry out safe and timely removal of obstructions, including vehicles and loads from roadways. Open Roads policies in Atlanta, Georgia; Indianapolis, Indiana; Miami, Florida; Minneapolis, Minnesota; Orlando, Florida; and Tampa, Florida included a roadway clearance target of “less than 90 minutes.” An additional target of “less than 35 minutes” was defined for minor incidents in Minneapolis. Traffic incident management personnel in Nashville, Tennessee reported a similar roadway clearance target of 30 minutes for minor incidents.

Comparatively, TIM personnel in Seattle, Washington aimed to maintain or reduce a 155-minute average for major incidents with durations exceeding 90 minutes. Roadway clearance targets in New Orleans, Louisiana and San Francisco, California included proportional qualifiers. In New Orleans, TIM personnel reportedly strive to clear the roadway within 30 minutes for 75 percent of all incidents. Similarly, the target RCT for TIM personnel in San Francisco was 90 minutes for 50 percent of all incidents. With few exceptions, participants in the TIM Performance Metric Adoption Campaign reported that roadway clearance performance targets were developed using convenient thresholds rather than more sophisticated methods based on historical performance data. In some areas—including Kansas City, Missouri; Pittsburgh, Pennsylvania; and St. Louis, Missouri—a desired “decreasing trend” in RCT is specified in place of a numeric performance target.

In order to calculate RCT, accurate determination of the “first recordable awareness of the incident” is needed. In the areas measuring RCT, this information was often obtained through the synchronization of or dual access to law enforcement (CAD) systems and transportation agency advanced traffic management systems (ATMS). In the case of dual access to CAD and ATMS systems, the earlier of the two notification times was used to indicate the first recordable awareness of an incident. At the time of the completion of this study, none of the metropolitan areas had fully integrated CAD-ATMS systems. Transportation agencies in metropolitan areas that do not have the data to support the first recordable awareness of an incident may be in a position to capture a modified measure of RCT. This modification reflects the time between when a transportation agency is first made aware of an incident and the first confirmation that all travel lanes are available for traffic flow. While a call for assistance to a 911 dispatch center is presumed to be the first recordable awareness for most incidents, transportation agency notification of the incident may occur take a few minutes, may be delayed, or may not occur at all depending on the nature of the incident. However, transportation agency notification typically occurs within a just a few minutes of a 911 call, leading to RCT estimates only modestly lower than the estimates derived using FHWA’s definition of RCT. Numerous participants from the TIM Performance Metric Adoption Campaign indicated a capability to begin collecting this modified measure of RCT almost immediately.

It should be recognized that a significant challenge to reporting RCT is that transportation agencies may not capture data for all incidents, rather they may only have data for those incidents that are reported directly to them. In Washington, for example, transportation agency personnel were estimated to respond to just 63 percent of all incidents. Incident data may also be limited to:

  • Distinct TIM programs, such as freeway service patrols (FSPs) or expedited tow programs.
  • Hours of transportation agency operation—many do not operate 24-7 and hence will not capture data for after-hours incidents.
  • Major incidents that typically require extended traffic control or involve roadway infrastructure/appurtenance repair or replacement.

Differences in the nature and extent of the data available to calculate RCT can result in a wide range of values among metropolitan areas. For example, an average RCT for major incidents will vary greatly from an average RCT for incidents handled by an FSP program. In Ohio’s three major metropolitan areas, TMC operators reported recording only “estimated” incident start and end times to support the Statewide Buckeye Traffic traveler information system, which is less exact than that needed to support improvements in TIM operations. When developing a national reporting system and database for RCT, these differences in the nature and extent of data forming the basis for RCT estimates should be carefully distinguished.