Bridges

Collisions of over-height vehicles with low clearance bridges is a worldwide problem. They have caused injuries, fatalities and serious damages to infrastructures. To mitigate risks, laser or infrared based detection systems, in conjunction with visual warnings such as flashing lights, illuminated signage or water curtains have been proposed and implemented. Nevertheless, some drivers ignored these visual warnings and collisions continue to occur. This paper presents a novel concept of collision prevention system which makes use of a series of smart, motorized rumble strips. These rumble strips span across a certain distance ahead of the low clearance bridge. Under normal conditions, these rumble strips are lowered and the pavement is flat. When an over-height vehicle is detected, a mechanism is triggered which elevates the rumble strips. The noise and vibrations produce a vigorous alert to the driver. They also increase effective friction of the road surface, thus assist to slow down the vehicle and shorten the stopping distance. The strips will be lowered after a certain time has lapsed, thus minimizing their effects on other vehicles. To illustrate the concept, a scaled model using ultrasonic detectors and electrical actuator is presented. The circuitry and mechanical design of motorized rumble strip system is discussed. It is demonstrated that the proposed new system is viable and envisage a full-scale study.