Comment by IshKebab

It is very hard to think clearly about driving too fast given both how much fun it is and the monumental amounts of money that the car industry has pumped over decades into promoting their empty road, drive fast without consequences propaganda within our societies.

However, as with tobacco, the evidence cannot be papered over forever and there are many studies that indicate they are a bad idea (tm) in urban environments. And in particular with respect to the setting of speed limits that they should be lower than many of us have been influenced to think because the rate of injury and death increases disproportionately with speed.

For instance https://www.who.int/news-room/fact-sheets/detail/road-traffi... states that a "1% increase in mean speed produces a 4% increase in the fatal crash risk and a 3% increase in the serious crash risk". And that for pedestrians "The risk of death for pedestrians hit by car fronts rises rapidly (4.5 times from 50 km/h to: 65 km/h.".

So yes, slower is safer - not in some reductio ad absurdum sense that implies '0mph', but in a public health sense where a fair and practical compromise should be sought.

To my mind, 15 - 20mph in urban areas is that compromise.

It allows practical vehicle use, while also respecting the rights of other road users - especially pedestrians and cyclists - to exist and move about without significantly elevated risk.

The idea that some people should be granted the ability to move through shared space at speeds that make them dangerous beyond anyone else simply because they're encased in a car is not just unfair - it creates noisy, dangerous, and ultimately unliveable environments.

My problem with the 20mph speed limits in the UK is that they seem to be imposed fairly randomly.

There are many cases where wide roads with good visibility and few pedestrians crossing have 20mph limits. In one egregious case I experienced recently near identical stretches of the same road (it was a main road, I think an A road, passing through a built up area) switched between 20 and 30 mph limits. If anything it created a significant distraction keeping track of the limits.

There are a number of other roads like that have 20mph limits. On the other hand narrower side roads in the same areas has 30mph limits.

My road has a 20mph limit. On the bit I live on it makes no difference - narrower, parked cars etc. means you drive very slow anyway. Further down the road is broader and clearer. I think the reason maybe to encourage people to use the bypass instead of driving through the village so it may be reasoned- although I suspect the speed bumps are more effective at doing that.

20-to-30 causes a step change in pedestrian outcomes, so no, the logical conclusion isn't 0mph. Also the average speed on 30mph roads before the changeover was around 20mph.

It improves traffic flow and reduces pollution too.

My only objection is that it's been applied in a somewhat blind way. Long sections of road with no houses and no reported accidents should probably be 30, or even 40mph.

I think we do in practice apply 0mph (i.e. banning cars) in some major cities, turning roads into pedestrian areas! 0mph happens!

It's obviously a trade between various participants, who have their own interests. 30km/h limits have had good success. If people think the number of fatalities is a problem, there's a solution waiting for you.

> But if "slower is safer" is the only argument for 20mph then the logical conclusion is 0mph.

Hilariously wrong. Kinetic energy is equal to mass times velocity squared divided by half. That squaring of velocity kills your argument.

Speed, of course, affects not just how many accidents there are but also how bad they are. A key argument for 20mph is that collisions with pedestrians at this speed are mostly survivable. https://publications.parliament.uk/pa/cm200102/cmselect/cmtl...