Why not figure out what distance it takes to get going say 30MPH and install speed bumps at those intervals? They hurt if you go over them to fast so its a disincentive to do so.
speed bumps are garbage for speed control, you need to make the cars weave with alternating bollards or curbs. Traffic circles and roundabouts use this method to reduce dangerous collisions.
For small streets with no lane markings: bollards placed on both sides so cars have to stop to let other cars through.
For large streets - lanes that weave near pedestrian crossings with curbs or jersey barriers force drivers to slow down and turn work best.
Sing it with me, folks…
You 👏 can’t 👏 reduce 👏 the 👏 speed 👏 limit 👏 without 👏 also 👏 changing 👏 the 👏 street 👏 geometry! IT DOESN’T FUCKING WORK!
People don’t give a shit about the what the speed limit sign says; they drive at the maximum speed at which they feel safe and comfortable based on the lane width, curve sharpness, etc. If you want to slow people down, you HAVE TO physically change the road – narrow it, add chicanes, etc. – to make it “feel” less safe. It’s not fucking optional!
(Source: my background in traffic engineering.)
your background in traffic engineering included learning how much these modifications cost.
seems like if we can’t have your ideal we get nothing.
yeah, thanks, nope. but thanks for the ovation.
You seem to be under the impression that changing the speed limit sign is “better than nothing.”
It’s not.
It is, in fact, worse than nothing because having half the drivers comply with the lower speed limit and having half not creates a mix of speeds that’s even more dangerous than if everybody just drove at the same higher speed.
I’m dubious and don’t care enough to take the time. whatever mr traffic engineer, I guess we just can’t have nice communities because it’s even worse to TRY.
do you have any idea how pathetic it sounds? like a cult of apathy, doing anything is GOING TO COST MONEY genius… and even if it doesn’t work perfectly, it’s still better to try than throw your hands up in the air and accept dead pedestrians all the time.
you do you tho.
Absolutely right. My town just made every road 25mph. Great. Unfortunately nobody gives a fuck. The road out in front of my house just got repaved. It’s beautiful. I love it. Pulling in and out of my driveway has never been better. People also blast down it, mainly because I think they perceive speed differently on a nice smooth tarmac versus what was a cratered surface rivaling the moon. My suggestion to my neighbors is we just keep cars parked on the street all the time. If folks in opposing directions need to stick to a side to let others pass, it will naturally cause them to move more slowly.
Edit - Forgot to add, I listen to traffic engineers testify pretty regularly and consistently get mistreated, so I just want you to know that I appreciate what you’re saying and what you do.
My house is on a residential 25mph street with a slight S curve. There was a car parked at the end of the curve and a reckless driver managed to plow into it and flip their car. It was the wildest thing I’ve ever seen. You would expect something like this on an interstate highway, not a tree lined street with little kids playing.
Speeds should be set using the 85th percentile rule: the speed limit is whatever speed the 85th percentile driver goes.
The thing, though, is we should work backwards from figuring out a desired speed for pedestrian + cyclist safety and then build a road with the desired 85th percentile speed.
Too often, it’s done exactly backwards.
It’s easy, just require speed governors in cars.
Where I live, they’re required in e scooters and e bikes, which are far less dangerous than cars
E-scooters and e-bikes don’t have speed limits that vary by street. In order to implement a governor capable of limiting a car to a 20 mph speed in certain areas while still allowing it to run at highway speeds in others, you’d need either a computer vision system to read the speed limit signs or a GPS paired with a perfectly complete and up-to-date speed limit geodatabase, and you’d need to give either such fallible computerized system control over the throttle (which could be a safety hazard in and of itself, for multiple reasons).
The difference between a e-bike governor and a car governor that can be set to something lower than 70 mph is like this.
Just have a 20 mph limit in the city, and no speed limit outside the city. This would also require moving all the highways outside the city, but I think that would be an improvement.
I largely agree with you, but I also recently saw this article: https://www.euronews.com/next/2023/07/26/inventive-or-stupid-french-village-disorients-drivers-with-crisscrossed-white-lines
That seems more like an “and” than a “but,” since it’s a physical change to the road that makes it feel less safe. Anyway, nice find! I like how inventive and relatively inexpensive it is.
To be clear, I’m not saying that the goal of reducing speeds is bad. I’m just saying that attempting to do so on the cheap by changing the rules instead of the built environment itself accomplishes nothing but to generate more lawbreaking. Well, that and potentially making the road even less safe than it was before because having a wider mix of speeds is even worse than having everybody at a uniformly too-high speed.
Step 1: reduce speed limit
Step 2: always have speed trap in place
Step 3: profit
And do you slow down? If so, we just need stupid cheap speed cameras and deploy them fucking everywhere
Given that we know going over the speed limit raises your collision rate, meaning setting the speed limit so low every driver will go over it is genuinely dangerous, do we have any studies supporting the claim that reducing the speed limit reduces the collision rate overall? I couldn’t find one, but it’s a surprisingly challenging search - I easily found studies confirming that collision lethality scales with speed, but that’s not my question.
Purely anecdotally, the vast majority of my collisions have been at very low speeds - in parking lots.
My main concern with this is that what you’re doing is desensitising people from the speed limit.
I’m from a country that has arbitrarily defined speed limits and VERY low compliance rates compared to the UK (if you’ve ever been to Italy for example you know what I’m talking about). The nice thing here is that because the vast majority of roads have a speed limit that ‘feels’ appropriate (ie the road is designed for its speed limit), the amount of speeding I see here is negligible compared to what I was used to.
And generally here when the limit changes people comply to it because you can trust there’s usually a good reason.
There’s roads near me that are arbitrarily set to 30 (no pedestrian walkways, no side roads, but it passes near the back of houses and I assume they successfully petitioned the local authority to change it to 30), and traffic flow there is usually 40-45. I’ve never seen an accident there.
We have a poorly designed intersection not too far away and there’s always accidents there to the point that there’s now a consultation to fix it.
If this rule came to England, both these roads would be turned to 20, and that won’t really be solving anything. In the first example I assume locals will still be driving 40, and it will create unnecessary overtaking because the road is wide and the visibility is good so it’s not necessarily unsafe. But you’ve gone from a safe 40 road to risking head-on collisions pointlessly.
Purely anecdotally, the vast majority of my collisions have been at very low speeds - in parking lots.
The fact that you talk like you have enough samples to make that inference worries me.
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Why will every driver go over 20mph/30kph? Are they incapable of maintaining that speed? All school and community zones in my country are 30kph; are we wasting our time with those?
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I’m a vision zero proponent, so I don’t care about the number of collisions; I care about the number of fatal collisions first, serious injuries second, minor injuries third. So even if 20 mph maintains, or even increases collisions; so long as it reduces casualties, it’s positive. Bumpers are replaceable; people are not. The AAA document you link even says a 10% reduction in mean speed reduces fatal crashes by ~34% in the executive summary.
Regarding the first point, drivers naturally trend towards the speed they “feel” is right. Also many modern cars practically idle faster than 20 once you get rolling.
Change the actual road to slow people down and reduce accidents.
I agree, but you are making excuses for bad driving. It’s still their fault that they drive too fast.
One of the problems is that a lot of cars have trouble driving at that speed. It’s really difficult to get them to remain at a constant speed under 25 mph or so, which can end up being extremely frustrating for the driver and encourages them to go faster than the speed limit. I realize this is a car design problem, but it’s still a problem at present until that is fixed.
Why would to need cruise control under 40kph?
The very fact it is signed so low should be a signal to the driver that this is an area which requires an increase in attention paid to surroundings.
You answered your own question. So I can concentrate on my surroundings rather then having to try to precisely control the speed of a car that’s not in TCC lockup.
Because otherwise you’ll likely end up either speeding or constantly staring at the speedo…
Is this a European car thing or a driver skill issue? As an American I’ve never had a problem maintaining slow speeds in any vehicle I’ve driven - manual or automatic.
Edit: I am starting to realize that some drivers are startlingly dependent on cruise control to maintain a target speed.
This is almost certainly not a European thing. A lot of people here still drive manually and just idling in 1st gear gives you a steady 7-10km/h… or “walking speed” as used in really dense and mostly pedestrian areas cars are still allowed to use. Idling in 3rd gear is around 30km/h (~19mph).
As an American, I sure have. Including my current Prius which doesn’t drive consistently between about 5 and 25 mph. And that was true of my previous Honda Civic as well.
Are these newer models or in poor condition or something? I’ve driven well maintained older Prius, Civic, and Accord vehicles without these issues and I LOVED how the Civic handled all around.
Tons of European cities already set-up speed-limit to 30 km/h. It’s not just large cities, I’ve seen villaged limited at 30 too.
it’s basically less nuisance for the residents
