It has certainly happened to you that you were driving by a sigh saying the speed limit is 40 while you were driving 45, but it’s probably not because you were inattentive. Talking about lane width and visual/physical geometry, I’ll help you understand why we tend to drive over the authorised limit.
Image of someone driving over the speed limit
The width of a car is of about 2 meters. A highway lane’s is of about 3.6 meters. This width allows us to travel at high speeds without being scared of getting out of our lane. Logistically, to reduce speeds, you’d want to narrow down the road, so drivers get scared of getting out of their lanes, therefore getting them to go slower.
Unfortunately, this detail is often forgotten about. In my hometown of Alma, in Quebec, a regular residential street often has a width of about 11m, or 5.5 meters per direction. It’s half wider that a highway lane, while expecting us to drive 3 times slower. The city put in signs to say the speed limit is 40km/h as opposed to the 50 it was, but most drivers are ignoring them and driving 50 to 55km/h.
Photo of a pilot project in Newmarket, North of Toronto, in Ontario
In the summer, the city places bollards to narrow down the road, and it works! This goes to show that narrowing roads slows down drivers. But how to incorporate this principle on a bigger scale, all while keeping the street looking nice?
A popular solution in North America is what we call a road diet; basically, paint more lanes and lines, like by adding a dedicated left turn center lane, or by adding white lines do the right sides of the road that could be used as cycling paths, sidewalks, or parking spaces. Those solutions don’t cost a lot, though they don’t change the road profile either.
Another often used solution in America or Europe is to change the road profile entirely, often by adding trees to separate the sidewalk/ cycling path from the road, all while making it look better, and slowing down cars.
Van Brunt Street, New York City
Indeed, a good way to narrow down a road and add a cycling path is to separate both by a green patch. Like on the picture. This modification makes the landscape prettier while reducing speeds and augmenting it’s capacity, as a bike takes way less space to transport the same number as 77.5% of cars in North America, as they’re only used by solo drivers.