Determining pre-impact acceleration and braking performance values is an important aspect of reconstructing collisions. Collision analysts may have to rely upon performance testing of an exemplar vehicle for reliable data to use in traffic collision reconstruction cases. These performance characteristics are well documented for many vehicle classes, but are limited when discussing urban transit style buses. The constant stop and go urban driving conditions in which they operate constantly challenge the vehicle components. Because of the heavy weights and operating conditions, auxiliary braking systems are often installed to prolong the life of the service brakes.
A series of idle acceleration, maximum acceleration, and maximum braking tests were conducted using urban transit style buses that are currently in-service in a large metropolitan area. The initial braking target speed for these braking tests was 64 kph (40 mph). The idle acceleration data was collected at measured distances to determine both acceleration values and top speed achieved due to idle acceleration. Data was collected using onboard instrumentation, video, and ground measurements. Both straight and articulated buses were tested using the same test methodology.
The results of these tests are reported in this paper. Some performance characteristics documented during these tests were then compared with results of other similar performance testing of comparable buses. This data will assist traffic collision reconstructionists with determining reasonable base values in analyzing collisions involving these types of heavy vehicles.