Wednesday, February 3, 2016

Pedestrian fatality risk as function of car impact speed

quick post today: Mikefc has created a very nice interactive chart showing pedestrian fatality risk as function of car impact speed using multiple risk models. Some of you might find it useful, specially for those involved in discussions/studies on road speed limits.


2 comments:

Fabio Storino said...

The biggest change seems to be when reducing from 50 km/h to 40 km/h.

In my city the "40 km/h zones" have been increasing in number. But with our historical lack of capacity for enforcement, this is bound to be dead letter (like so many other good laws) and runs the risk of being reverted by future (and less visionary) mayors.

I struggle to understand why we don't replace our speed radars, which are increasingly easy to bypass with technology (and also increase the risk of rear-end collisions), with a method of calculating the average speed on a said road.

We already have the plate readers in place, it's a simple calculation! And there's no reasonable way of beating it!

Dave H said...

Removing all signage and hierarchy for the use of road space has been noted to have the effect of slowing down most drivers in an area which requires a negotiated priority of movement to between 15 and 20mph.

There is also an evolved ability for the eye-brain interface to manage the images and angle of vision over which this is captured. As speed increases the focus narrows and cuts out close and peripheral detail.

We also have some pretty rough bits in a healthy adult - work in the late 1940's established that in a 'flat' 20mph impact the skull is only at 30% of its impact capacity.

All would appear to point to an evolved unaided operating speed of 15-20mph for homo sapiens - which is effectively the limit of fast running. Specimens who got badly damaged running into things or falling over did not reproduce, and equally operating at speeds up to running speed would appear to be the limit for safe mixing of all modes in a shared space. As the speeds go seriously above this level the transport systems need to be managed to increasingly tighter limits (ie rail = faster but guided more rigidly and on closely controlled system) and separated .