This report presents the final results of a multi-year research programme to investigate the crashworthiness of transit buses and to support evidence-informed approaches to enhancing occupant protection.
Five frontal offset transit bus crash tests were conducted with decommissioned buses at 40 km/h and a 40 %, driver-side offset. The test parameters for the two pairs of crash tests (Test 1 & Test2; and Test 3 & Test 4) were matched except for some structural strengthening that was added to the front end of one striking bus from each pair. Test 5 was a non-matched test conducted to supplement the dataset, and study the influence of seatback geometry.
The strengthening of the bus reduced the intrusion into the driver occupant space and resulted in a redirection of load to the upper body and a reduction of loading to the legs of the driver. The strengthening resulted in negligeable changes in peak acceleration (<2 g) of the passenger compartment of the bus. In all tests the acceleration of the striking bus never exceeded 10 g. All dummies placed in the passenger compartment of the striking bus (with the exception of a restrained dummy in a wheelchair) either impacted the seat in front with the head or were ejected from the seat.
A sled buck representing a section of a transit bus passenger compartment was constructed so that, through controlled sled testing, the dummy responses could be examined in greater detail. The similarity of dummy motions between the bus crashes and the sled tests suggests that the dummy motions observed in the buses can be reproduced on the sled. Crash pulse severity, the dummy posture and seat placement (inboard vs. outboard) were all found to influence the response of the dummies.
The sled data was used by the University of Waterloo to develop and validate a finite element model to compare the simulated motions of the human body model to the physical dummies. Impact of the neck with the handrail which was observed in the physical testing cannot be detected by the instrumentation of the physical dummy. Simulation of the neck impact with the human body model however identified a risk of injury to the larynx.
The study demonstrates that there are important potential opportunities to improve the protection of occupants in low to moderate severity bus collisions. Modifications to the structure of the bus will not be sufficient to reduce the risk of head impacts. Resources should instead be directed towards optimizing the interior of the bus to provide better energy absorption when the head strikes occur to improve passenger protection in the most common transit bus collisions.