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.
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?
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.
But similarly, human behavior can be trained. We aren’t NPCs. These bad drivers could be taught to drive at a safe speed regardless of the width of the street, through stricter education and enforcement. Pedestrians/cyclists/homes/businesses around the street -> drive slow, that should be an instinct.
Enforcement doesn’t work for what I’m describing, without conscious effort, humans drift to the speed they think they need. Always. So whenever you try to policy it, you are asking folks to go against their nature.
Change the shape / characteristics of the road to change the speed people drive it.
As I said, I completely agree that changing the shape of the road is an important component of this solution.
Yes, I am asking the operators of deadly heavy machinery to put in a small amount of conscious effort to keep people safe. Why is that an impossible request?
No one in my state complies with the speed limits because they’re ridiculously low for the design of the road. You have a road built to handle 90mph but you tell people to go 30mph? Yeah that ain’t happening
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.
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.
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.
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.
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.
2006 Civic traded in for a 2016 Prius. Maybe you’re better at handling a car than other people, but my subdivision is 20 mph the whole way through and I have never myself or been behind anyone who can drive that speed consistently. It’s always plus or minus 5 mph, usually wavering between them. I don’t think all of the dozens of drivers in this large subdivision are bad drivers.
That still sounds like a design problem if it requires skill to just drive consistently at 20 mph. Why should that require skill any more than driving consistently at 30 mph?
You actually think it requires skill to drive at 30 mph? Because I was able to do it pretty well the first time I ever stepped behind the wheel of a car.
Yes I do believe it takes skills to safely hurtle serveral thousand pounds of steel through a neighborhood. You must keep the vehicle between the lines, maintain adequate following distance, look for and follow signs and signals, and have a high reaction time for anything that may cause a potential collision like another car, cyclist, or pedestrian. There is a lot of hand-eye coordination, a knowledge base, and physical capabilities required to drive safely. Driving is a skill. It is something someone learns to do through experience like any other skill.
Now you are moving the goalposts. We are talking solely about driving at a consistent speed. That is something novices can do without a problem at 30 mph.
Driving at a consistent speed requires skills to do it safely. Unless you are exclussively driving under controlled conditions where nobody else has access to use the street, you need a base set of skills.
I can’t believe you’re actually saying driving 20 mph takes significant skills. That’s ridiculous and if it’s true, then 20 mph shouldn’t be expected of anyone.
Yup it is a skill and one that studies show people tend to overestimate their abilities with. All the more reason to invest as a society in alternative transportation and heavily cut down on the overall number of drivers behind the wheel.
I don’t see why it’s a big deal. The streets near me that are 20 mph are all residential streets with stop signs, driveways, and street parking. You’re almost never going a consistent speed for more than couple hundred feet anyway.
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).
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.
You don’t have to precisely control the speed, just keep it between 0-20mph. Your speed should be dynamic based on what is coming up anyways. Are you just turning on cruise control from the intersection and leaving it until you brake the next time?
I have never even considered using cruise control on anything other than a highway. Am I the one driving wrong?
No, it’s just a different style. It’s like 1 pedal driving with the brake pedal. It would work particularly well with an electric car where the first part of the brake pedal is regen braking.
Skill issue! I have no problem maintaining low speeds in my car lol. Honestly, for the safety of those around you, please take a driving course so you can safely practice driving at low speeds.
I envy your commitment to saving fuel. I would be on the gas in 2nd so I don’t have to faff around changing down when I hit a hill or have to slow down for whatever reason.
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
Regardless of anything else, there are no circumstances under which companies like Uber would decrease traffic. This is because of two effects: Firstly, any regular car ride replaced with an Uber ride will result in more road-hours, since there is now a car travelling to your pickup point as well travelling on the road after dropping you off.
Secondly, the convenience of Uber can cause more travellers taking a car instead of public transport, again increasing the total number of road-hours.
Is there even a hypothetical scenario under which any of these private hire companies would reduce traffic? The only theoretical benefit is that less parking spaces are needed.
Electric bikes are generally pedal assist. They require you to pedal, but make it as easy to pedal up a hill as to go on a flat street.
They’re less exercise vs a regular bike, but you still get a good bit of exercise. Perhaps more exercise, if the e-bike causes you to bike something you would have driven instead.
Robotaxis? Probably not. But autonomous vehicles that can communicate and drive as a group? Yes that will help. Then induced demand and all that, but it will increase capacity.
Robust public transportation will help a lot more. But go ahead and argue with the MIT scientists who wrote this article if you like. Their research seems to show you’re wrong.
We have this speed limit in the Netherlands, mostly in areas with housing. It doesn’t really affect busses because they stay on the bigger roads that are 50 kmh (about 31 mph). In my opinion it’s fine to drive 20 mph on the more local roads, as long as there are collector roads where you can go a bit faster.
Public transit has been lacking in my city even before the pandemic. They are still paying off for a light rail system from a decade ago that they are not maintaining. Also all the ticket machines smell like piss, which should not be a surprised considering for years there’s been some guy who has been urinating at almost all the station.
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