Maybe in Japan it will be effective. Since their "zone 30" creation was apparently a success, it seems probable that people will generally comply. My experience in France differs.

I live in a French town where the default speed limit is 30 km/h instead of the national 50 km/h. In the street where I live, the drivers that willingly (sometimes they can't overtake bikes and slow cars) observe that limit are a tiny minority. Why would they, since there are no automated controls in the city, and police sets manual controls once in a blue moon.

My street was already at 30 km/h in 2016 when the global speed limit was introduced by the city council. I'm pretty sure the mean speed has increased since then, though I don't have hard facts to prove it[^1]. At first I thought that, since all road signs were removed except on the city borders, the drivers needed a constant reminder of a limit that they'd prefer to ignore. Now I just think that people soon saw that there was almost no risk in breaking the law.

[^1]: There was a study, but the methodology was so poor that it was inconclusive. They monitored the speed in a dozen streets before and after the change, but it was done for different lengths of time (one or two weeks), at different times of the year, and with explicitly no attention payed to potential popular events or roadworks. So the average speed was globally lower after the change, but in most streets it had increased!

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maratc 9 hours ago | parent | next [-]

Street bumps are much more efficient in lowering speed than either "automated controls" or "manual controls". You (plus neighbours, probably) could petition your council to put one (or several) on your street.

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buran77 9 hours ago | parent | next [-]

The elegant way to implement such a speed limit is to have the driver do a "slalom" between things like trees or parking spots set alternatively between the two sides of the street, or green islands in the middle of the street. It forces a low driving speed without the discomfort and potential damage caused by speed bumps.

Street bumps are a discomfort even for those who respect the speed limit, and sometimes for residents (more noise) so they don't have popular support unless it's a problematic area, with a low safety record. There are high tech bumps that incorporate a radar sped detector and instantly raise in front of speeding cars but there are costly and require more maintenance.

	▲	maratc 9 hours ago \| parent \| next [-]
		I pass three speed bumps on my street every day. I'm driving at low speed, and the bumps are designed so to not create discomfort at these speeds. I don't even brake before them. They only create discomfort to people who drive way above the limit, which is the whole purpose, and the bumps are very effective at that.
	▲	ndsipa_pomu 3 hours ago \| parent \| prev [-]
		Yes, the idea is to provide drivers with clues as to the relevant speed. Straight roads are usually designed to prioritise motorised vehicles and often need speed limits to try to control the drivers. By designing in chicanes and narrow sections, drivers don't usually have to be told to slow down. Also, having plenty of trees makes roads a lot nicer and you may even get free road bumps from their roots.

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eloisant 9 hours ago | parent | prev | next [-]

Street bumps are no longer allowed in France. Existing ones can stay, but cities can't create new ones.

Instead they create bottlenecks and turns to force cars to slow down.

	▲	maratc 8 hours ago \| parent [-]
		You are likely referring to prefabricated rubber speed bumps, outlawed because the material becomes very slippery when wet, endangering motorcycles, scooters, and bicycles. Asphalt and concrete street bumps seem to be legal in 30 km/h zones. Here's an offer from Citroen which is free and "open to all 34000 French mayors via an online form": https://www.youtube.com/watch?v=f-AI70ImUgE

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trgn 9 hours ago | parent | prev | next [-]

My street has speedbumps since a few years and its been an amqzing improvement

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sam_lowry_ 9 hours ago | parent | prev [-]

Street bumps damage cars, make noise and create even more pollution. I head of a neighborhood action were drivers were honking on newly installed speed bumps. Until they got removed.

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Sharlin 9 hours ago | parent | prev | next [-]

Reducing the speed limit often does little in itself because the v85 (85th percentile of speeds) is more dependent on how fast drivers feel it is safe to drive. Streets should be (re-)designed so that the limit and drivers’ intuition match, but that, of course, takes time and money (and will). Still, it’s much more economical in the long run than active monitoring/enforcement.

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verytrivial 9 hours ago | parent | prev | next [-]

I'm a busybody. I have bought radar guns from eBay. I have lightly shamed the local authorities with data. There are now more physical speed controls (more signs, speed bumps, one way roads) in my local area. Perhaps my nagging helped. I like to think it did. Start chipping away at it. If not you, then who?

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PetitPrince 9 hours ago | parent | prev | next [-]

It will probably never happen, but maybe it's a way to facilitate the creation of traffic calming infrastructures (chicane, bump)? There's not better way to reduce the average speed than being forced to pay attention to not ruin your car (see the sibling comment with a picture of a narrow Japanese road)

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zuck_torrenter 9 hours ago | parent | prev [-]

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