Comment 99808

By kevlahan (registered) | Posted April 04, 2014 at 10:43:41 in reply to Comment 99804

By freeway speeds, I meant the 70-100km/h design speed of the major arterials. And these city streets are obviously not actually safe to drive at 100km/h, even if the lane widths, lack of controlled intersections make it possible!

And even the minor arterials, at a design speed of 70km/h is designed for typical highway speeds (80km/h).

There can be a bit of an extra margin (say 10km/h), but designing a major arterial for up to double the legal speed limit is a recipe for disaster: there is just no way this speed is safe, especially for pedestrians and cyclists who have to share this road!

The danger of these high speeds in a dense urban setting is just basic physics ... and, in case you are wondering I do have a PhD in applied math and physics ... my research area is applied mathematics and scientific computation for physical phenomenon such as fluid flow and fluid-structure interaction (and I am an associate member of the mechanical engineering department at McMaster).

You don't need to be a traffic engineer to understand that roads designed for double the speed limit will encourage speeding, or that the risk increases with the speed squared (i.e. a driver speeding at 70km/h is at least 2.5 more dangerous than a driver obeying the speed limit at 45km/h both because reaction times are less increasing the chance of a collision, and because the energy is higher making the collision more damaging).

And in some countries, like Australia and the UK, the posted speed limits are actually rigorously enforced.

Comment edited by kevlahan on 2014-04-04 10:55:13

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