A collision at a lower speed is less severe: simple as that.

A less severe collision lowers the chance of a fatality and lowers the severity of other injuries.

Arguing that an imperfect (or partially effective) measure shouldn't be implemented is disingenuous.

That ignores that they are specifically targetting the highest risk roads, which would likely increase the likelihood of being in that 15%.

I don't really understand this Matthew-Wilson guy's argument:

"Speed cameras seem like a magic solution, but they're not: they alienate ordinary motorists without affecting the behaviour of the tiny minority who cause most fatal crashes," he said. "The sad fact is: the idiots who cause most fatal accidents tend to ignore speed limits anyway." A 2009 AA analysis of fatal accidents found these crashes were caused by "people who don't care about any kind of rules. These are men who speed, drink, don't wear safety belts, have no valid licence or WoF – who are basically renegades."

And then he says

Matthew-Wilson said he favoured speed advisory signs, which simply show motorists what speed they're doing, without issuing a ticket.

"The fact is, most drivers will slow down if you remind them that they're going too fast."

So he's saying people obey road signs, and speeding is only really done by these special outlaw people who dgaf about anything we do so there's no point in even trying?

I kind of wonder what he's basing this theory on.

He cites that study from 16 years ago but if they are able to categorize these people then surely catching them and taking them off the roads would be a good idea?