A404 Weight-Activated Automatic Signaling

High Wycombe Safety Scheme

This integrated system is designed to warn heavy vehicles of a steep decline as they travel down a steep hill on the A404, leading into High Wycombe. The steep hill has been the cause of several serious accidents caused by runaway heavy vehicles.

At the apex of the hill SSL have deployed a real time weigh in motion system that collects vehicle data including vehicle weight and speed. When vehicle weight exceeds a configurable threshold, three LED signs commissioned by SSL are activated alerting the vehicle driver as the vehicle passes down the hill. The LED signs warn the driver to get in low gear, and emphasize the hazards associated with steepness of the hill. Only one sensor system is needed for all three signs; the bespoke system software calculates the optimum interval for activating the signals from the measured vehicle speed.

The system is also able to activate the signs based on a combination of speed and weight parameters or just speed. E.g., only trigger the displays for heavy vehicles traveling at a potentially hazardous speed.

The bespoke control and monitoring software application was written by SSL. It is designed for ease of use at the roadside and includes an IP rated touch-screen / membrane keypad user interface. The application creates logs of event data, including vehicles, sign activation events, plus faults and statistics. The application can be remotely monitored and daily log files downloaded for offsite analysis.

Although this was an innovative project and the first UK system to combine vehicle activated signing with real time weigh in motion, it was completed rapidly by SSL with very little trouble. The system was installed and commissioned within 3 months of receiving the order from Buckinghamshire County Council.