Highway 7 - Kitchener to Guelph

[ijmorlan]

De facto speed limit 120km/h

But regardless, there needs to be some difference between the design specification and the actual for safety factor. You don’t want routine usage to be running right at the limit.

Of course I don’t expect the interchange ramps to support 100km/h, although I suppose some of them could.

That kind of logic makes sense if you treat traffic engineering like bridge engineering, which quite frankly is exactly what traffic engineers do.

The problem with that is the load is not a physical mass, it's a group of people operating vehicles.

So yes, the road should be forgiving to a higher speed than the speed limit, bUUUUUT that's a far more subtle thing than the "design speed".  Specifically, the "apparent" design speed should be the speed limit, if you want people to travel at the speed limit.  

The same applies here as applies to residential areas.  The only real difference is the "innocent people" put at risk by drivers who drive too fast on the highway is almost exclusively people in other cars, as opposed to pedestrians, cyclists, and after this morning, building occupants.

I do suspect that highways are far harder to make the apparent design for a given speed, and speed limits and enforcement become more important.

Yes, excellent point, and I would agree that a big problem with our cities is that we allow traffic engineers, in effect, to design many aspects of the city. Whereas instead the road design and drivers should have to live with what is good for the city as a whole. Example that occurs to me: on the highway I understand signs are designed to break off in the event of a collision, and this is good design. Whereas in the centre of the city, I think it would be preferable if poles would stop a car dead before it hits a pedestrian. If that’s a problem for its occupants, they shouldn’t have been driving that fast.