METHODOLOGY

Performance measures studied included Roadway Clearance Time (RCT) and Incident Clearance Time (ICT), as well as Response Time (RT). These performance measures were calculated for IMT responders for 320 incidents in 2018 and 289 incidents in 2020. In addition, data regarding the affected volume (AV) associated with incidents, the excess travel time (ETT) accumulated due to incidents, and the excess user cost (EUC) associated with incident congestion were gathered. In 2018, 188 incidents were analyzed for these user impacts, and in 2020, 144 incidents were analyzed. Data collection of the traffic incidents occurred from March to August in both years on I-15, US 89, I-80, SR-87, I-215, US-6, US-40, and I-84 highways in Utah. Statistical analyses were conducted to compare IMT performance between the two years and explore the associations of the AV, ETT, and EUC with IMT.

FINDINGS

• The results showed that with a 208 percent increase in coverage area due to the IMT expansion, IMT was able to respond quicker to incidents. The percentage of incidents that IMTs responded to within 15 minutes of a crash occurring increased from 58.8 percent in 2018 to 65.9 percent in 2020, for a 12.1 percent improvement.
• The statistical analyses estimated that for each minute of RT in 2020, 14.66 minutes of ETT and $394.93 of EUC were saved. These savings translated to approximately 32,985 hours of ETT and $53,315,550 of EUC, with a median response time of 15 minutes.
• The results of the statistical analysis estimated a percent reduction in the averages of AV, ETT, and EUC, as shown in Table 1. Table 2 shows that a one-minute reduction in response, roadway clearance, or incident clearance time with associated savings in ETT and EUC. Overall, this study found that having a greater number of IMTs available does have direct benefits in reducing ETT and EUC.

Table 1: Average User Impacts for 2018 and 2020

Table 2: ETT and EUC Savings