Driving 10 mph above the speed limit on a highway at every opportunity will only lead to a very limited reduction in travel time, because you spend a lot of time breaking (i.e. to avoid crashing into law-abiding drivers, reacting to speed controls, etc.).
At the same time it drastically increases both the risk of accidents, as well as the severity of accidents when they happen. You also endanger not only yourself but also everyone else on the road with you.
Sensible road design takes this into account and constructs roads in a way that disincentivizes speeding and is safer for everyone. One example would be "lazily" meandering highways instead of perfectly straight ones. The broken sightline is a great incentive to keep your foot off the gas, most people do it instinctively.
"Ongoing driver training" on the other hand is burdensome and expensive for the individual drivers and will probably lead to little noticeable effect, as speeding is not related to "not knowing better", but to "feeling entitled to break the rules" (for whatever reason).
Failure to drive 70 mph on a highway posted at 60 will (very often, road depending) result in far more cars overpassing you. Each instance of passing carries a small but definite amount of risk; it is safer to match the speed of the other cars on the road than to obstinately stick to the limit and get passed hundreds of times in a single trip.
(As for ripping up roads and relaying them so drivers intuitively find the safe speed to match the posted speed limit, it would be much cheaper to simply adjust the speed limit than establishing entirely new right of ways through existing neighborhoods, farms and industrial zones. That would be bonkers.)
It's a rare stretch of American interstate highway where the majority are sticking to the speed limit. On different roads the ratio of speeders to "speed limit doers" varies, but interstates have fairly consistent driving conditions and the safe speed for those conditions is consistently higher than the posted limit.
Usually traffic on American interstates is staying at the speed limit if: there is a fair amount of congestion, everybody is stuck behind somebody doing the limit, or there is rain/fog/snow/etc.
>and the safe speed for those conditions is consistently higher than the posted limit.
A cursory look at traffic safety statistics would seem to dispute this statement. The US consistently ranks quite high in traffic fatalities, which seems to indicate that you couldn't safely drive faster than the current speed limit in most circumstances. Of course you'd have to control for a lot of other factors for a definite conclusion, but conversely, I'd like to see an actual source for your theory.
Enforcing a speed limit is actually not that hard if you want to. You can of course put stationary or mobile speed cameras in place. But even better may be systems I've seen in some places in southern Europe: Cameras at the beginning and end of a stretch of highway that compare time stamps of your passing and calculate the average speed of your car in that stretch. If you've passed the stretch quicker than should be possible according to the speed limit you'll be fined. It's quite low tech, cameras are prevalent on the highway systems of many countries, anyway, and it solves the problem of people adhering only to the speed limit if they know they are being observed by law enforcement.
There are a number of interstates (and interstate like US highways) near me that have posted speed limits of 70MPH but any normal day you'll find traffic going 55mph or even less.
When everyone is driving beyond the speed limit, the ones actually obeying the speed limit are the dangerous drivers. It is unfortunate that speed limits in the US have not corresponded to how people actually drive since 1973.
How does this make sense? If I'm driving the speed limit and someone else is crashing into me from behind while speeding, they are the dangerous driver. No matter how many other people also ignore the speed limit.
Also, increasing the speed limit does nothing to make traffic safer. That doesn't make any sense at all, as increased speed is correlated very well with increased accident rates and severity of traffic-related injuries:
It should be obvious that driving substantially slower than everyone else would make you a danger to others. Try driving at the speed limit on a high way in southern NY, especially in the left lane. You will have many near accidents and the reality is that you would be the dangerous driver for not keeping pace with everyone else.
Increasing the speed limit to the 85th percentile so that you do not have the few people who actually obey it posing a hazard to others does make things safer.
Getting cars off the road sooner by reducing travel time, decreases the number of cars on the road. This increases the distance between cars and accidents only when the distance betweeen a vehicle and something else reaches 0. Forcing people to drive slower therefore causes collisions by bringing cars closer to one another.
The severity is a separate matter from whether there is a collision. As for severity, people drive much faster in Germany where there is no high way speed limit for much of the autobahn yet their autobahn network has half the fatalities that U.S. highways have. The safety data from 2012 shows this:
As for your link, it talks about pedestrian safety. As per the data there, pedestrians are unsafe on highways no matter what the speed limits are. There are also no pedestrians on highways. There is no point to setting highway speed limits based on studies showing the danger to non-existent pedestrians.
Did you post the first link that seemed to agree with your position as part of some fallacious appeal to authority because logic failed to agree with your preconceived notions that you were never equipped to defend? I suspect that is exactly what you just did.
At the same time it drastically increases both the risk of accidents, as well as the severity of accidents when they happen. You also endanger not only yourself but also everyone else on the road with you.
Sensible road design takes this into account and constructs roads in a way that disincentivizes speeding and is safer for everyone. One example would be "lazily" meandering highways instead of perfectly straight ones. The broken sightline is a great incentive to keep your foot off the gas, most people do it instinctively.
"Ongoing driver training" on the other hand is burdensome and expensive for the individual drivers and will probably lead to little noticeable effect, as speeding is not related to "not knowing better", but to "feeling entitled to break the rules" (for whatever reason).