Are Variable Speed Limits Worthwhile?

Over the holidays, we drove from Vancouver, over the Coquihalla Highway (Highway 5), for a ski trip to Big White, just east of Kelowna. The summit of the Coquihalla is renowned for its steep grades on approach to the summit, the great bear snowshed that protects a section of the road from avalanches, chain up areas, high snowfall, dangerous driving conditions, and many collisions as a result of all of that. The BC Ministry of Transportation and Infrastructure recently installed variable speed limit signs along part of the route. The goal was to "improve driver safety during unfavourable weather conditions and to reduce serious crashes in areas where weather patterns are prone to change quickly, making driving conditions dangerous". Here are my thoughts on it after driving through in less than ideal conditions.

The BC MOTI Website explains how the system works...

"A regular posted speed limit is a maximum speed set for ideal conditions. Variable speed limit signs display the legal speed limit when road and weather conditions change, for example, during snow or rain events.

Static message signs at the entrance to each corridor inform travellers they are entering a variable speed zone. A Digital Message Sign (DMS) at the beginning of each corridor warns drivers of changing weather conditions.

Flashing lights installed above each variable speed limit sign are activated when a reduced speed limit is in effect.

​Traffic, pavement and visibility sensors monitor real-time traffic speeds as well as road and weather conditions to provide recommended reduced speeds back to operations staff who then adjust the electronic signs to let drivers know what speed they should be travelling for the current conditions.

All signs and sensors have backup power, but should a power outage occur, or a speed sign is blank, drivers are to maintain the speed of the last posted speed sign.

Even with a variable speed limit system, it is important that drivers know to travel to the conditions of the road, their vehicle, and their abilities."

When the conditions are good, the posted and variable signs show a 120 km/h maximum speed. This time on a snow covered roadway the signs were being used to reduce the speed limit and on our way into the interior of BC, the signs were showing a speed limit of 60 to 70 km/h over the pass.

Regardless of the signs, the speed limits shown were about the speed I was travelling. Makes sense given that vehicle speeds are used to set the posted variable speed. With a desire not to end my life, my wife's, or others nearby through bad driving, or even just a desire not to damage our car, I was driving to the conditions more than the signage.

On the way back home, travelling westbound on partially snow covered roads, the speed limits varied from 80 to 100 km/h and I was likely driving a little slower than the signs suggested. My feeling here was that these speeds were not comfortable. The traditionally posted static speed limit is a limit in ideal conditions and not a recommendation for all conditions. With the variable signs, given they are based on the conditions they are essentially saying it’s safe to travel at the speed shown. In all likelihood it would have been, but in the conditions, I wanted more margin for error.

So based on my brief time driving through the corridor on snow covered roads, my assessment is that most people with a reasonable level of self-preservation will drive at a sensible and safe speed regardless of signage. That speed will vary slightly based on experience, confidence, vehicle and tire capability.
Those that exceed the posted speed in good conditions may well exceed the variable speed in poor conditions unless it is enforced. I don’t think the guying going 140 in the summer will go 140 in winter, but he may still go 20 above the variable speed. I’m not sure the signage will have a great effect on driver behaviour.

Also, while speed is often a significant contributor in many collisions, bad tires, poor judgement, impairment and distraction will continue to result in collisions regardless of speed.

​Will the new signs make a difference to safety, I predict it will be very small, but I guess time will tell...