Simulator Study of Heavy Truck Air Disc Brake Effectiveness During Emergency Braking

In crashes between heavy trucks and light vehicles, most of the fatalities are the occupants of the light vehicle. A reduction in heavy truck stopping distance should lead to a reduction in the number of crashes, the severity of crashes, and consequently the numbers of fatalities and injuries.

This study made use of the National Advanced Driving Simulator (NADS). NADS is a full immersion driving simulator used to study driver behavior as well as driver-vehicle reactions and responses. The vehicle dynamics model of the existing heavy truck on NADS had been modified with the creation of two additional brake models. The first was a modified S-cam (larger drums and shoes) and the second was an air-actuated disc brake system. A sample of 108 CDL-licensed drivers was split evenly among the simulations using each of the three braking systems. The drivers were presented with four different emergency stopping situations. The effectiveness of each braking system was evaluated by first noting if a collision was avoided and if not the speed of the truck at the time of collision was recorded.

The results of this study showed that the drivers who used the air disc brakes had fewer collisions in the emergency scenarios than those drivers using either standard S-cam brakes or those using the enhanced S-cam brakes. The fundamental result that this research validates can be phrased as: “Reducing heavy truck stopping distance decreases the number and severity of crashes in situations requiring emergency braking.”