How often do you drive the posted speed limit? If you’re like most drivers, not often.

Why do we speed?

This is probably a more complex question than my short summary will answer, but in the following is a lot of truth.

People drive their vehicles to just under their tolerance of risk. If a road is in great shape and the geometrics (curvature, sharpness of hills and sags, curve super-elevation, etc.) are good, we drive according to these conditions. We often complain about the slow driver (who is obeying the posted speed) clogging up the roadway.

In the political jurisdictions where I live, highways and a lot of roads are purposefully designed to a higher standard than the posted speed limit. The advisory speeds are also set lower than the geometric design.

I’d say typically. Freeway design speeds are 20 km/h above posted. Trucks are speed limited to 5 km/h above posted and probably the majority of cars drive close to 15 km/h above posted. Secondary routes are a bit trickier. Primary two lane highways most likely have the 20 km/h cushion. Regional roads will be designed with anywhere from speed limit plus 20 km/h to as low as speed limit plus 0 km/h.

There is a clause in the Ontario Design Manual that states “A design speed equal to the maximum posted speed is acceptable …. for minor collector and local roads.” A common Canadian design manual recommended posted speed plus 10 km/h. Assuming you can safely drive 20 km over the posted speed is not a given.

At what speed do the police ticket speeders? This probably varies depending on time of month, traffic, etc., but I heard from the horse’s mouth that often freeway speeds up to 19 km over the posted limit are not bothered.

It appears that the condition of our roads, the allowance permitted by our law enforcement, the fact that truck speed limiters are set higher than our posted speed plus our propensity to drive to the edge of risk all lead to most of us breaking the legally established speed limits. Speed limits as presently set do encourage law breaking.

There are some jurisdictions that have increased freeway speed to somewhere just below the road’s design speed. The actual average speed increases less than 2.5%. This is as a result of those who actually obeyed the lower speed limit now moving at the new “reasonable” speed limit. Also, the accident rate has not increased.

With the speed limit was set properly, there would be no assumption that a driver can speed safely.

In order not to promote law breaking, speed limits should reflect the road’s geometrics. If the speed limit is reasonably set, the police then should enforce it. No exceptions. With cruise control, we can keep a steady speed. With the low cost of GPS units, we can know our speed accurately (I have a vehicle where I think the manufacturers set my speedometer wrong on purpose).

There is no need for anything but say 3 km/h leeway. The police should be out there, visible (ie no hiding – entrapment) and tagging anyone speeding.

Speed limits should encourage compliance not promote law breaking.

The Plaidneck