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...

30 km\h limit in densely populated and heavily used by pedestrians first\last 2-5 minutes of your travel does what? Extends your travel time by 1 minute? At the same time making it nearly impossible to kill a kid, cat, dog or human in these places.

Same goes with the right of way in these places. You're in a car, you're getting where you're going much faster anyway, so you let pedestrians go first. On pedestrian crossings, and often even without them in such "last leg" places.

It's completely logical. You don't go faster in places where somebody can suddenly walk out from behind a parked car, bush, whatever. But it's a cultural thing in Scandinavia.

There was a study [0] in Paris that demonstrates a signifiant life expectancy and positive benefit/risk ratio of bicycling or commuting by public transports: the effect on physical and psychic health largely outweighs (sometimes to x30) the risk of accidents and pollution disease.

> without transport

Nobody argues to remove all cars altogether, and certainly not other forms of transport. However we certainly can rethink the millions of individual cars in each cities: does everybody needs its own 1ton vehicle to bring food back from the local supermarket? To go to work 2-20km away?

[0] (2012, french) https://www.ors-idf.org/nos-travaux/publications/les-benefic...

It's almost as if a balance could be achieved, both by reducing the number of cars and increasing the number of trains/busses.

Since there really are no traffic jams in Finland, my experience is that the phenomenon is worse here. In more populated countries drivers must deal with sometimes occurring reduced speeds like adults, but in Finland there usually is enough space for a single driver to keep their speed at 115% of the limit, due to other drivers facilitating the selfishness. If someone does not facilitate, the speeder will get aggressive and has to find someone to blame for their (actually, his and his car’s, which has more civil rights than a leftist) misfortune.

In Germany all drivers have to accept that there isn’t enough road capacity so everyone could drive as fast as they want and the Staus cannot be blamed on the car in front of you. It’s also common to drive under the limit, in Finland 115% of the limit is the socially acceptable minimum.

People not used to it. On my school run some will do 20-60 depending on where along the road and how narrow and what the sight lines are. Others will just do 20-30 for the whole 10 miles.

At a couple of locations there’s morning room but lots of room to overtake (as long as nothing comes the other way), the road is nearly wide enough to have a line down the middle. Most drivers are fine but some of the 20-30 lot will swerve all over the road to try to block overtaking.

These aren’t super narrow, you can get a tractor or hgv down the whole road, and even at some passing places get one past another.