Closed Loop and Pilot Field Study Assessed the Safety Impacts of ATMA for Florida Work Zones Using Dashcam Recordings, ATMA Log Files, Drones, and Manual Inspection.
Automated Truck-Mounted Attenuators (ATMA) offer potential benefits for safety and operational improvements in mobile work zones by eliminating the need for a worker to operate an impact protection vehicle. The automated (driverless) ATMA system operates in a multi-vehicle leader-follower configuration where the truck-mounted attenuator truck is retrofitted with a variety of sensors and cameras that enable its automated capability. The human-driven leader vehicle transmits navigation data to the follower (driverless) ATMA vehicle using Vehicle-to-Vehicle (V2V) communications. This project piloted a demonstration of the ATMA technology on June 23, 2020, and evaluated its operational and safety functions in a closed loop course, as well as testing the feasibility of ATMA in active mobile work zones throughout Gainesville, FL, over a course of several weeks. A benefit-cost ratio was calculated based on crash reduction potential of ATMA over traditional Truck-Mounted-Attenuators (TMA), using crash data for Missouri, from 2012 to 2017, and crash cost data from Florida DOT (FDOT) from 2012 to 2016. For cost estimates, vendor-provided equipment, installation, and maintenance cost items were considered for FDOT’s pilot ATMA deployment.
In this project, FDOT’s Gainesville maintenance and regional transit system bus depot was selected as the closed loop site, where a total of 26 test cases were designed to test safe following accuracy (without crashing and without going off the intended path) of the driverless ATMA vehicle on straight, slalom style, and circular paths, going forward and in some cases in reverse. In addition, six sites of active work zones were selected for field tests, where the study deployed the ATMA technology to shield the Falling Weight Deflectometer (FWD) test equipment. Dashcam recordings, ATMA log files, drones, and manual inspection were used to collect a variety of data including time, location, speed of the follower and leader vehicles, traffic characteristics, and behavioral data. The benefit of the ATMA was calculated based on yearly mitigated crashes.
- The results from the benefit analysis revealed savings of $273,080 due to reduced crashes by using ATMA instead of TMA, assuming 50 operational TMA vehicles with a life cycle of five years and an estimated total of 3,520 average yearly number of work-zone-related crashes (potentially mitigatable and avoided by deploying ATMA) for FDOT.
- The closed loop test results revealed that, among the 26 tests, the ATMA performed as expected in 23 scenarios (88.5 percent success rate). In one of the three unsatisfactory tests there was a critical error due to emergency stop failure and the ATMA vehicle going off track.
- The results from the field tests showed that, three out of the six total tests were completed as expected (50 percent success rate), however, there were exceptions to three others due to the ATMA vehicle drifting off the intended path and misinterpretation of a hard brake as a collision.
- The results from the benefit-cost analysis revealed an estimated benefit-to-cost (B/C) ratio of 0.93 (a B/C ratio less than one means costs exceed benefits) considering the present values of benefits and costs in an illustrative scenario of 50 TMAs being operational. The reason for the low value of the benefit-to-cost ratio could be attributable to the outdatedness of the input data used for the benefit-cost analysis and to the use of Missouri based TMA related crash percentages due to the lack of detailed FDOT TMA crash data.