Posted speed limit signs advise motorists as to the maximum speed considered safe for travelling on roadways under normal operating conditions. They establish the speed limit in which motorists can react to potential driving problems that they may encounter.
Each year, municipalities receive numerous requests to have stop signs or traffic control signals installed to reduce speed.
However, contrary to popular belief, the purpose of stop signs and traffic control signals is to assign the right-of-way at intersections — not to control speed.
In general, it is very difficult to control speed. Speed limit signs do not slow down traffic, reduce collisions or increase safety.
Research has shown that most drivers travel at a speed they consider to be comfortable, regardless of the posted speed. Studies undertaken "before" and "after" revised speed limit signs have been posted, have shown that there are no significant changes in average vehicle speeds.
In effect, speed limits between 50 km/h and 80 km/h are determined based on traffic engineering surveys. These surveys analyze roadway conditions, collision history and vehicle operating speeds. A safe and reasonable speed limit is usually set at or below the speed at which 85% of drivers travel. Installing the inappropriate control device or arbitrarily lowering the posted speed limit will result in drivers speeding between control devices to make up for lost time.
Traffic flowing at a uniform speed increases safety and results in fewer collisions. Drivers are less impatient, pass less often, and are less likely to tailgate.
Lowering speed limits beyond the recommended levels produces a more dangerous situation. There is a wider range of speeds between those driving the posted limit and the majority of motorists driving at what they feel is reasonable for the road characteristics.
The posting of the appropriate speed limit simplifies the work of enforcement officers, since most of the traffic is moving at the posted speed. Blatant speeders are easily spotted, safe drivers are not penalized, and police officers are not asked to enforce and defend unrealistic and arbitrarily posted speed limits.