A model of truck speed profiles on short upward slopes

Abstract

Truck speed reduction on upward slopes increases the crash risk. Existing speed–distance models estimate speed reduction on upward slopes by assuming that the resistive forces equal the tractive forces. In this case, the truck speed is a minimum and is called the crawl speed. This paper describes the calibration of a speed–distance model on short upward slopes using data obtained with a GPS device. The calibration was performed for trucks with a weight-to-power ratio of 95–160 kg/kW and for operating speeds of 70–93 km/h at the beginning of the upward slope. The results show that on short upward slopes, the minimum speed was 1·15 times higher than the theoretical crawl speed. The model was also used to obtain the required length for a speed reduction of 15–40 km/h, which is useful for establishing the need to provide climbing lanes on short upward slopes.