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
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.