The Development of a Wet Weather Speed Limit Trial on a NSW Freeway
An analysis of crashes on the 6 km section of the Sydney to Newcastle or F3 Freeway north of the
Hawkesbury River Bridge to Mount White between 2000 and 2004 has shown that there were a total
of 134 crashes. Long term climatic data from the nearby Bureau of Meteorology Automatic Weather
Station showed that on average 32% of days each year experience rain in this area. In contrast 57% of all crashes in this area occur in the rain, this is substantially higher than what would be expected.
Almost 60% of all crashes occurring in this area when it is raining have had speeding identified as a contributing factor to the crash compared to only 27% of crashes that occurred in fine weather.
A key outcome of the New South Wales Road User?s Summit held in March 2005, was for the NSW Roads & Traffic Authority (RTA) to develop a Wet Weather Speed Limit trial on the northbound lanes
of the Sydney to Newcastle Freeway between the Hawkesbury River and Mount White.
The demonstration project utilises Variable Speed Limit (VSL) signs, weather stations, pavement
moisture detectors and static signs to reduce the speed limit to 90 km/h limit when raining. The 90
km/h wet and 100 km/h dry speed limits are enforced by a new fixed speed camera.
Major challenges in introducing a wet weather speed limit included the high cost of electronic VSL signs, calibration of equipment, incidence of electrical storms in the area and remote monitoring of the geographically isolated scheme by the RTA?s Transport Management Centre in Sydney.