The study results from the TIM Performance Metric Adoption Campaign (9) showed that participants in 16 metropolitan areas reported using a definition for ICT consistent with FHWA’s definition, although some of the consistency had only recently been achieved. Under FHWA’s definition of ICT, the time at which an incident has been cleared is determined when the last responder has left the scene. Results from the TIM Performance Metric Adoption Campaign show that the definition of “last responder” varies among metropolitan areas, and sometimes from incident to incident. The last responder may include transportation, law enforcement, or towing and recovery personnel. For example, TIM personnel in Greensboro, North Carolina; Minneapolis, Minnesota; and Portland, Oregon consider an incident to be cleared when the last transportation agency responder—often an FSP operator—has left the scene.
Comparatively, TIM personnel in Cincinnati, Cleveland, and Columbus, Ohio consider an incident to be cleared when either the last transportation agency responder or the last law enforcement agency responder has left the scene. In Salt Lake City, Utah and Baltimore, Maryland the last responder may include transportation, law enforcement, or towing and recovery personnel. In Providence, Rhode Island the incident is considered to be cleared when “most” responders have left the scene; therefore, this may exclude a single law enforcement officer who remains on-scene to complete reporting functions. Finally, recorded ICTs sometimes include the time for queue dissipation, as was indicated by participants from Los Angeles and Salt Lake City.
Cincinnati, Cleveland, Columbus, Greensboro, Nashville, Portland, and San Diego reported an overall ICT target of less than 90 minutes. In Salt Lake City, performance targets for ICT were reportedly distinguished by incident severity: less than 90 minutes for an incident involving a fatality, less than 60 minutes for an incident involving an injury, and less than 30 minutes for an incident involving property damage only. In Houston, the goal for the SafeClear Program was to remove 98 percent of disabled vehicles from the roadway within 90 minutes and 70 percent of disabled vehicles from the roadway within 20 minutes. TIM personnel in Fort Lauderdale, Florida adopted a letter grade scheme for representing the performance with respect to incident clearance—incidents cleared in less than 60 minutes receive an “A,” and incidents requiring more than 120 minutes to clear receive an “F.” Distinct, increasing time ranges between 60 and 120 minutes are assigned corresponding to “B,” “C,” and “D” letter grades.
As the calculation of ICT and RCT are based on the same start time – the first recordable awareness of an incident – the same challenges exist with calculating ICT as they do with RCT, including the determination of the “first recordable awareness of the incident” as well as the nature and extent of the data available to calculate ICT. In Houston, Texas a collection of data to support the calculation of ICT was limited to the SafeClear Program (Houston’s freeway service patrol) and was defined as the time between when the SafeClear tow operator is notified of an incident and the time the disabled vehicle is removed from the roadway. An additional challenge identified by TIM personnel relates to the accuracy of last responder departure times from the scene. While these data are often captured through routine communications or closed-circuit television (CCTV) surveillance, delays in reporting or observing departure of the last responder can produce inflated ICTs.