This paper examines the in-service braking behaviour of heavy vehicle drivers to provide information for use in the development of design rules, which would improve tractor/trailer braking compatibility under routine braking regimes. Results show that while braking is required every 500 m under heavily trafficked urban driving conditions, on roads with high levels of service this can reduce to once every 11 km on average. Under the right road and traffic conditions, heavy vehicles were shown to travel up to 90 kms between brakings. Average braking duration was between 6 and 9 seconds with average deceleration rates of between 0.4 and 0.7 m/s2. These decelerations are considerably less than the 0.25 g accepted as the limit of comfortable passenger car braking, as well as those within which the current Australian Design Rules for truck braking are framed.
Abstract