3 ms·
20mph is considered to be good for survivability, but is not really good from a speed/travel perspective. I believe OP meant maybe 40mph is a good balance betw
by Closi 4y ago
20mph is considered to be good for survivability, but is not really good from a speed/travel perspective.
I believe OP meant maybe 40mph is a good balance between the two factors of speed (higher is better) and survivability (higher is better) from a corporate risk / insurance perspective.
Raising one of these lowers the other - so the actual threshold depends on how you value speed / convenience vs accident survivability / risk, and what you want to market your car as able to do (few consumers will see a 20mph self-drive speed limit as a viable self driving system).
- zip1234 4y ago20mph is within populated areas and not on a main road. In the US, the norm is 25mph, which isn't that far off.
- hgomersall 4y ago25mph is >150% of the energy at 20mph. It's a big increase.
- FabHK 4y agoAnd not only that. In a situation where, with 20 mph, you can just come to a complete stop before the child, with 25 mph initially you'd hit it with 15 mph. vr = (c^2 - 1)^0.5 v1 where v1 is the original slow speed with which you'd come to a standstill just before the obstacle, and v2 = c*v1 is the faster speed, and vr the speed with which you hit the obstacle coming in with the faster speed (assuming you hit the brakes at the same spot, and constant deceleration).
- hgomersall 4y agoIndeed, as an interesting aside it's a 3-4-5 triangle. 25^2 - 20^2 = 15^2
- Closi 4y agoThat comes with it’s own challenges - ie limiting speed to 20mph in the UK would realistically mean it can only be used in areas where there are schools and lots of pedestrians - ie less chance of an incident being fatal but possibly more chance of an incident.