Driving in montana before the state implemented a max speed, I'd have my cruise control set at 100 mph. I remember seeing limos pass me like I was sitting still.
I miss those days.
I miss those days.
Going 110 on a dry empty highway? Carry on.
Going 110 on I-90 right outside of Billings? Pull over young man, its time for the highway patrol to have a philosophical discussion with you on the side of the road.
On a US highway you can glance in the mirror and see a vehicle, and you can work on the assumption that it's not going (much) more than 65mph. Or see a gap and have a general idea of how long you know it will still be a gap. Having a massive variety in possible speeds harms that.
I think many people seem completely unaware about how fast a car at 110mph (for example) can appear. It's in the order of time it takes to check your blindspot and other mirror - there's a hard limit to how many directions you can be looking at one time after all. No amount of "Personal Driving Skills" or "Being More Aware" can help that if the timing is unlucky.
Probably for the best, they do have 80 mph speed limits now, but lots of drivers there still drive like there's no speed limit.
There are also some other roads that are not included in these figures because they are not classified as Autobahn, but Autobahn-like carriageways. Germany has around 3,350 km of them, a few without speed limit.[2]
[1] Source: ADAC report from 2024-04-22 (in German), see https://www.adac.de/verkehr/standpunkte-studien/positionen/t...
[2] For examples see the German Wikipedia article "Autobahnähnliche Straße" at https://de.wikipedia.org/wiki/Autobahn%C3%A4hnliche_Stra%C3%...
Speed limits are an imperfect tool for an important problem. They were generally much higher, or nonexistent, on US highways before the 1973 oil crisis [0]. They were intended to save fuel, but weren't very effective. Nowadays, most people discuss them as a safety tool.
They aren't great for that, either. Speed disparity is the best way to cause an accident, with those going at least 5MPH under or 15MPH over the 85th percentile speed being the most dangerous drivers on the road. Limits force people to choose between going a comfortable speed and following the rules. When the difference between comfortable and legal speed is too high, you get situations where raising the limit can reduce the rate of accidents (citation discusses stats, my suggested reasoning is more speculative) [1]. There are still of course many cases where setting a slower speed limit has reduced accidents [2], but that effect is not universal. Also worth considering is that, even if higher limits reduce the rate of accidents, accidents at higher speeds are almost universally more severe.
Consider long, straight, flat roads with 2+ lanes on each side, a median, no sidewalks, infrequent turn and/or merge lanes, with ample room to speed up or slow down, and speed limits of 50 MPH or lower. There are several near me. They are painful to drive, because they breed traffic tickets, tailgating, and accidents. Hell, the people on either side of the "go a comfortable speed" and "go a legal speed" even fight each other, making rolling roadblocks to slow traffic, or giving way to road rage.
Either raise the limit, or add curves, trees, sidewalks, bike lanes, etc to convince people to slow down. I tend more towards the "I can't drive 55" side [3] because I think it's generally better for the economy when people and goods can move faster. Edit: For a specific example, from Kansas City, the 9+ hour drive to Colorado Springs or Denver (at 70MPH) makes it nearly impossible to go there. There's very little traffic on I70 past Topeka. Without a speed limit, I could easily do the trip in a little over 4 hours in my C350. That would be FANTASTIC for the economies on either side of that stretch (not to mention along it).
If you're not familiar with Brock Yates and his influence, check out [4, 5, 6].
[0]: https://en.wikipedia.org/wiki/National_Maximum_Speed_Law
[1]: https://www.sciencedaily.com/releases/2018/12/181212135021.h...
[2]: https://jalopnik.com/iihs-finds-that-lowering-speed-limits-a...
[3]: https://youtu.be/RvV3nn_de2k?si=mLYQIkwlHCDPr6ec
[4]: https://www.caranddriver.com/features/columns/a15143608/the-...
Obviously this is true, and especially important at low speeds, but I wonder how much difference there is between 70 and 80 — I would have assumed they are both typically fatal
One of my favorite trivia is the scenario that a car going 50 mph sees an obstruction in front and slams on its brakes and stops just in time just tapping it. A car next to him going 70 mph sees the same object, has faster reflexes, and hits his brakes at the exact same spot of the road. He slams into the object at 50 mph.
Just the difference between 70 and 80 is the energy of going almost 40 mph.
That's when the issue is stopping distance.
The issue on highways is that you have, for example, two cars in the left lane going 55 MPH and a third approaches going 70 MPH. One of the slower cars sees this and moves over but only at the same time as the faster car is changing into the same lane to pass on the right, so now both lanes are blocked, the faster car hits one of them and they're both edged off the road into a stationary object at highway speeds.
Does it matter if they hit the stationary object with significantly more energy? Probably not; dead is dead.
Meanwhile a significant proportion of accidents happen not because you couldn't stop fast enough but because you couldn't stop at all. Another driver side swipes you and rams you off the road and you're now three feet from a head-on collision with a utility pole; if you can even get your foot to the brake before impact it's not going to save you. You're driving on an apparently clear road in winter and come across a patch of black ice; your brakes have no effect and you're hitting whatever's in front of you at full speed. It's night, you're tired and you only realize there is a completely dark disabled vehicle in one of the travel lanes when you smash into it.
In cases like this the difference between 30 MPH and 50 MPH can mean a lot, but the difference between 55 MPH and 80 MPH is basically just "you're still dead".
No, kinetic energy is only quadratic in the velocity, E = ½ mv².