Truck adaptive following distance based on threat assessment under variable conditions

Vehicle-stopping distance and recommended following distance are important factors for heavy-duty truck safety. The practical vehicle stopping-distance is affected by several factors beside vehicle dynamics: current speed, braking system retardation force, road slip and road grade. One of the purposes of truck onboard monitoring is to provide real-time feedback to the driver that could have two forms: a warning to the driver for any threat of frontal collision; or advisory information. Both are based on threat assessment and thus are equivalent in theory. Most previous work in the literature only provides threat assessment and warning under ideal cases that is, flat, straight, dry and concrete road surface conditions. The authors systematically investigate vehicle stopping distance under variable conditions, based on which the corresponding recommended following distance is generated. Although it is difficult for the driver to estimate the following distance visually, sensor detection plus appropriate feedback to the driver can achieve the same goal. Practical implementation issues and field test results are also presented. They show how significantly the environmental factors affect the threat assessment and the recommended following distance. The results are readily applicable to the development of safety systems for other types of vehicles.