Heavy-Vehicle Gap Control for Bridge Traffic Loading Mitigation

The study of traffic congestion has principally emphasised the effects on traffic operation and control, safety, economic and environmental issues. The effects of traffic congestion on road infrastructure, however, have not received as much attention. The development of Intelligent Transportation Systems has the potential of drastically reducing bridge loading and extending the lifetime of ageing structures. This work proposes and investigates the benefits of a warning system that alerts heavy-vehicle drivers when the gap to the front vehicle falls below a certain threshold. Such a gap control system may be applied to mitigate bridge loading or improve safety in tunnels. The traffic stream has been modelled by means of traffic micro-simulation through an ad-hoc formulation of the car-following Intelligent Driver Model. The benefits of the gap control system in bridge loading mitigation have then been analysed. The minimum gap between trucks should be adjusted according to site-specific traffic features and to the safe load the bridge is able to carry. The results show that a 10% compliance of trucks to the gap control system instructions reduces the total traffic loading on a 200-m span by about 10%. A near-50% reduction of the total load can be attained when 90% of the trucks are compliant. Hence, the proposed system represents a promising and effective alternative to the traditional sign-posted bridge weight limits, thereby enabling significant savings in avoided freight traffic restrictions and structural maintenance costs.