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.
Reasonable and prudent is objectively the best speed limit.
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.
110 MPH is never a safe speed for a car on a highway. Crash rate increases exponentially with speed. At 110 MPH you are placing your life and the lives of other road users at risk for no real good reason.
The #1 thing for driving safely is being predictable. Too many people seem to think "driving safely" is mechanically being able to control your car on the road, but that's the easy part. The difficulty is there are other people on the road all taking their own independent actions.
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.
To be exact: Out of 25,758 km Autobahn in Germany 18,115 km have no speed limit (70.4%) and another 1,608 km (6.2 %) have gantries without speed limit under favourable conditions (construction sites not taken into account).[1]
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]
That's actually a much higher percentage without speed limit than I expected. I wonder if the stretches without speed limit are usually order traveled and thus less experienced. Anecdotally I used to drive between Bonn and Paderborn a lot and the speed limit would only go away once out of the densely-populated Ruhr area.
I never really got to enjoy those days. The path I'd typically take through Montana had a speed limit: 90 was about as fast as I could go and still get good enough MPG to make it to the next gas station...
What a perfect invitation to get on one of my favorite soapboxes. Spoiler: I'm a big fan of Brock Yates.
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].
> Also worth considering is that, even if higher limits reduce the rate of accidents, accidents at higher speeds are almost universally more severe.
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
The energy is exponential. It takes 30% farther to stop going 80 than it does going 70.
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.
Another related pet peeve is when I see cyclists going the wrong way in a bike lane. On a 40 mph road a cyclist has a differential with traffic of 20-25 mph. An accident would be serious by likely non-fatal. When you ride the wrong you you add the speeds and make nearly all collisions fatal.
> The energy is exponential. It takes 30% farther to stop going 80 than it does going 70.
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.
I guess that's theoretically possible, but even in that rare case, people are going to break if they hit someone. Driving too slow causes some accidents but they rarely lead to deaths. AFAIK, driving too slow is such a minor safety issue that no study has been carried out to ascertain exactly how bad it is though.
The trouble with that one is that it's the one caused by people driving too slow, and isn't rare. When people are driving at significant speed differentials to each other, it causes a lot of lane change maneuvers. Which are dangerous because each one is a chance to move into a lane without realizing there is someone in your blind spot, or that the new lane has an obstruction ten feet in front of you, or focus your attention on what's happening in the lane you're intending to change into and fail to notice an immediate hazard in the lane you're still in. So you get more accidents, and those accidents are still happening at highway speed.
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".
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.