Dynamic speed display signs are popping up beside B.C.'s Highways. They display the speed of passing vehicles above a sign showing the posted speed limit. Are these signs useful in persuading drivers to keep to the limit and if so, how effective are they?
According to a Ministry of Transportation and Infrastructure Highway Safety Engineer "These displays have shown effectiveness at reducing overall vehicle speeds shortly following installation. However, the effectiveness of speed reader boards is limited and decreases shortly after drivers pass the board. Longer term effectiveness has not yet been determined." Some studies have shown continuing effectiveness, while others show that success varies. In any case, combining the signs with law enforcement produce the best result.
An example is the sign on the Trans Canada Highway south of Nanaimo that precedes an intersection in an 80 km/h zone with a recurring collision problem. Prior to the installation of a speed reader board the 85th% speed was 96 km/h. Six months after installation, a before/after speed data comparison was carried out and indicated an 85th% speed of 90 km/h. In addition, the data showed that 53% of drivers were travelling less than the posted speed limit.
Hopefully these signs will prove to be a worthwhile investment on their own and coupled with regular speed enforcement contribute to a reduction in collisions.
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