Factor in speeds for turn penalties

[PinkDuck]

e.g. from 52.673645,0.957841 to 52.672091,0.945735 (https://goo.gl/maps/7ufJJ2FC7tC2)

While legal to make a U-turn in the above instance, it would involve slowing from 70 mph to <5 mph to cross wide hatchings then accelerate back up to 70 mph. A rather dangerous thing to do, yet the chosen route above from the public web demo.

Does the route timing currently factor in the need to slow down to make such a sharp turn?

Should such high back angle turns on high speed road simply be avoided through a separate penalty or implicit restriction?

Yes, I could add a no U-turn restriction to OSM, but it is legally possible to do it as exemplified by the emergency services.

[danpat]

We do have a turn penalty included in the car.lua profile now:

https://github.com/Project-OSRM/osrm-backend/blob/develop/profiles/car.lua#L439-L447

But it does not take into account the current speed. You're right, a U-turn at the location above looks like a bad idea.

We should probably think about factoring the speed values into the turn penalty for cases like this.

[TheMarex]

but it is legally possible to do it as exemplified by the emergency services.

You can also add exceptions for this case http://wiki.openstreetmap.org/wiki/Relation:restriction I'm not sure about traffic laws in England but this definitely looks like it should not be allowed for general traffic.

[PinkDuck]

The England traffic laws permit u-turns anywhere except where explicitly restricted by signage. Just that most drivers would realise that it is too risky to consider under normal driving. I could add restrictions but then this is quite a universal thing for any near 180 degree turn from 70 mph to 70 mph speed limit, so worth considering as a system factor.