This study from MIT used geo data collected from cars in Milan, Italy, to check the effectiveness of 30 km/h zones in reducing speed.
The first conclusion is that the signs don't work: 85 percentile speeds are all over the place in 30 km/h zones in Milan, as shown in the figure below:
The second step was finding correlations between speeds and street features extracted from openstreetmap. Results are as expected: narrow, short, curvy sections correlate with lower speeds, as do 1 lane vs more, one way vs 2 ways:
The final step is also interesting: the authors made a model to predict the compliance of 30 km/h speed limit on streets that are 50 km/h at the moment. Useful for urban planning to understand if charging an area to 30 km/h would need structural interventions (like bumps, narrowing of the street...) or not:
There is so much more in the article, I suggest to read it fully.
crossposted from: https://mastodon.uno/users/rivoluzioneurbanamobilita/statuses/114827312307353297
If the limit is setup appropriately. Loads of roads have the limit set where you would think the speed limit is 80km/h but somehow it is set to 50km/h. So everyone ignores the set limit. While at other roads the limit is say 70km/h but you can hardly drive over 50km/h.
The limit should be set to whatever is deemed safe for pedestrians and cyclists in a given location. The road design should then match that speed limit.
So the road should be redesigned to make it hard to drive over 50 (make it more narrow and add traffic calming)
This is Italy we're talking about, our public officials want zero responsibility so they always set absurdly low limits.
Point is, road design is everything, if you want people to go slow, you can make it so, if it's an area where people can go faster, design the road accordingly and keep it maintained, don't let it turn into a crater field, just to later "fix" the problem with a temporary speed limit.
In Milan this would be possible, since it is a rich city, in the rest of Italy, not so easy.
Sounds good TBH. If they also narrow the roads/remove lanes to enforce it, put bike paths/public transit lanes in the free space, and fine anyone driving dangerously, then this is the recipe for a good city.
I doubt people drive at 80 in a city, that's a rural setting. Do people drive at eight kph where you live? Fastest is 70 and that's basically a highway where I live
Yeah there are roads with 90 km/h speed limits within city borders. And people speed too. It's insane.
Although if you as a pedestrian ever try to cross a line of traffic going 60, it's also quite horrifying.
I believe the speed limit within cities should be 30 km/h by default, with very few exceptions. That puts people before cars, as it should be. And ideally we should strive to make public transit and bicycle infrastructure good enough to just ban personal vehicles in cities outright.
I say that as someone who owns a car and likes driving it. Cities and towns are just not the right place for cars. They belong on dirt country roads and off-road. Basically, if the population density allows us to build serious infrastructure for transportation, it doesn't make any practical sense to build infrastructure for personal motor vehicles.
That's a lot more than just putting signs up saying 30kph however. You're talking about a radical change
Yes, this is exactly what I'm advocating for.
lol