Road design, safety and Vision Zero

[danbrotherston]

I mean, the whole point is NOT to do that in order to slow traffic lol. For a turbo roundabout maybe a little contouring is expected. FWIW, I think islands on the four lane road would be appropriate, crossing four lanes of traffic is pretty dangerous. And I'm not sure of the scale, the crossings feel pretty far from the circle.

I'm curious, what did you use to create this? It looks excellent!

As drawn, trucks would be simply unable to navigate it at all. But on the other hand, slowing traffic at the pedestrian crossings is I think supposed to be a goal of roundabouts. So the splitting/curving should be done with both goals in mind, not just to make motor vehicles move smoothly.

What we really need is a design where the radius experienced by trucks is larger than the radius experienced by passenger vehicles (but still not so large that they can blow through without slowing significantly). I don’t have any brilliant ideas on how to make that work.

This is actually pretty simple to do, what it's called is "truck aprons", basically a curb where trucks are allowed to drive up but cars are not. They are already used in some places with traffic signals in the region (and much more broadly outside the region): https://www.google.com/maps/@43.4062017,...384!8i8192

They can be used in roundabouts as well if needed. Our roundabouts already use the mountable centre median to "allow" trucks to navigate which are too large for the roundabout.

I don't like these options all that much though...they don't provide a safe refuge for peds, and drivers tend to ignore them and just drive over them. They might allow our engineers the ability to make better designs, but only because they're insanely conservative already. For example, the intersection I linked can easily manage all but the largest of oversized vehicles without the truck apron, even without using the second lane, and given there is a second lane to swing into extremely oversized vehicles should just use that.

The same situation applies for our roundabouts. Unless they are literally moving a wind turbine blade, even the largest semi-trucks never mount the center median, so why did we spend money paving it?! What a waste!

I would point that out in Bytor's design as well, we don't know what lane widths are in use here, but even the conservative Dutch roundabouts use 5 meter lanes. So if that was the case in Bytor's design, and mountable curbs are used, I would argue even a large semi truck could navigate it, using both lanes as is but if a significant fraction of the traffic was large vehicles like semi-trucks, small affordances could make it navigable by semi-trucks using a single lane, if those trucks use both entrance lanes, which is also reasonable.

And if you need to accommodate the largest of oversized vehicles, you can again use an apron in the centre.

But when it comes to it, this insistence on accommodating the very largest of vehicles in the normal lanes (without using multiple lanes) is again, part of why our roads are so unsafe, our engineers (and other road users) should get used to oversized trucks using more of the road than would normally be permitted.