[IshKebab]

> The results are basically universally in favour of speed enforcement reducing motor vehicle collisions, reducing injury and cost.

Yeah this argument comes up a lot in the UK from people advocating 20mph speed limits everywhere. It's a super dumb argument though. Obviously increasing speed is never going to decrease danger. But if "slower is safer" is the only argument for 20mph then the logical conclusion is 0mph.

Clearly there are other factors at play, but the 20mph people never acknowledge that for some reason...

(To be clear I'm not advocating for 30mph everywhere. I feel like 25mph is actually the best trade-off for most suburban roads.)

[lonelyasacloud]

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.

[IshKebab]

> 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.

This is precisely my point. None of the "slower is safer" people even acknowledge that it is a compromise. Their entire argument is "slower is safer" which does lead to 0mph.

It's impossible to have a proper debate if some people are saying "I know slower is safer but I don't want to go at 20mph everywhere" and others are saying "but... it's safer!"

[graemep]

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.

[Mawr]

> There are many cases where wide roads with good visibility and few pedestrians crossing have 20mph 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.

Make up your mind ;)

[Dylan16807]

There are many cases, and the bit where they live is not one, but a nearby bit is one.

If you're making a joke I don't get it. Can you explain it?

[pbhjpbhj]

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.

[Dylan16807]

https://ars.els-cdn.com/content/image/1-s2.0-S00014575193010...

I don't really see a step change between 32kph and 48kph.

[IshKebab]

> the logical conclusion isn't 0mph

Yes it is. If the only thing you consider is safety then 0mph is the safest. That's unarguable.

The point is that you can't only consider safety. There are other factors, but they are often deliberately ignored.

[pbhjpbhj]

Well also we need to kill everyone so noone can die, the only logical conclusion.

If that's your best argument _against_ saving lives through road traffic controls then at least we know it's not wrong...

I hope your computer is completely unsecured, because if you cared about security you wouldn't even use the web.

[rtpg]

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.

[Mawr]

> 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.

[lukan]

Can you explain what you mean?

The argument is, going 0 mph, meaning not driving at all is safer than even slow driving. Meaning the argument is, there has to be a compromise, all driving is dangerous.

[gmac]

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...

[IshKebab]

> mostly survivable

Collisions at 15mph would be even more survivable though.