Re: FN-FORUM: [OT] Speed cameras and speed camera detectors

date posted 1st June 2003 10:07

Tony Jones wrote:
> James Fidell wrote:
>
>>Then why do fewest accidents happen where the speed limits are highest?
>>
>
> Well ....... that's probably because it's a relatively safe, hazard free
> section of road ..... hence the higher permissible speed limit :)
>
> However, referring to Ray McGinty's post:
>
>>Speed limits aren't there to spoil your day or to increase police
>>revenue, but to make roads safer for everyone (not just drivers).

This is an interesting question, that was anwered when my girlfriend was
sent on an "speed awareness training course" as an alternative to being
busted. She went off to the course as anyone would, feeling rather
cynical about it, but she came back as a much wiser and safer driver.

Basically, speed limits are mainly applied according to the chance of
vehicles hitting each other head on (other factors such as pedestrian
density also count, but not nearly as much). Apparently most road
fatalities occur due to head-ons - your boy racer who loses control,
leaves the road, and simply collides with the environment has a much
greater chance of survival. Sure, you've got your crumple zones, seat
belts, and airbags, but the human body can only withstand so many G's
before internal organs and blood vessels are torn apart. The forces
experienced when decelerating from 60 mph to zero by hitting an
immovable object are survivable. This is equivalent to two cars
colliding head on. As the cumulative speeds of two colliding vehicles
exceeds 70mph, death due to becomes almost inevitable.

A speed limit on a road is effectively a gamble - how frequently will
two cars collide head on, on a particular stretch of road? To put it
another way, let's say you can tolerate 0.2 fatalities a year (i.e. 1
every five years) on a given stretch of road. What speed limit needs to
be applied to meet this target? For example, on a motorway, the traffic
is segregated, there's a miniscule chance that you'll hit anything going
the other way, so the limit is 70mph.

If anyone wants to argue or to know more, I'm afraid I can't oblige, as
I only know what I was told. Also, before anyone starts quibbling about
G forces, I'm guessing that Jensen Button hitting a tyrewall is not the
same as a head on collision between two road vehicles.

Chrid

--
http://www.chridmeister.co.uk