Exploration of the factors associated with a parked unattended vehicle failing to remain stationary: brake cooling effects

ECE regulation 13H specifies that a laden vehicle must be capable of being held on a 20% gradient for 5 minutes with a maximum force of 400N applied at the manually operated hand lever. (1). However, anecdotal reports suggest that when an unattended vehicle fails to remain stationary, the period of time which has lapsed may be more than 5 minutes, and the gradient on which the event occurs may be less than 20%. A survey of drivers and driving instructors indicated that as many as 13% of respondents had experienced such an event (4). The aim of this study is to explore whether rear brake type and the effects of brake cooling affects the ability of the parking brake system to hold the vehicle stationary in real life driving conditions. The relevance of this in relation to driver interaction with the parking brake system and parking practice is then considered. [Continues.]