I don't know.

I drove throughout Germany a few times last year, and I didn't really understand why there were so many jams and general slowdowns. I usually drive in France where the highways are almost exactly the same as Germany (most often two lanes, frequently three, rarely more, usually in very good state) and traffic is rarely as bad. I got stranded a few times in completely still traffic, for tens of minutes, during a normal working day, while this only ever happens at the worst time of holiday traffic in France.

Maybe it's because French highways are paying which probably discourages some drivers, but I also noticed a lot of roadworks in Germany (almost as bad as Belgium during the height of roadworks there last year). Enough, as you said, to never be able to maintain a high speed for long, while you barely ever notice those in France. I don't know how French companies do it, but I'm pretty sure it helps with the traffic.

Other than the traffic though, driving in Germany was a pleasure. People are aware of their surroundings and don't drive like the road was theirs.

And the fact that the French highways require payment reduce trafic even more. But they are a joy to drive on. Set the CC and just go.

In Germany, the logistics clearly utilizes the autobahns a lot. You see constant lines of heavy vehicles on the rightmost lane, and sometimes your overtaking them is interrupted by one truck passing another one, very very slowly as they both have a speed limiter, just adjusted slightly differently.

I'm pretty sure Germany is trying to use less road for a lot more cars and everything else is secondary with regard to traffic jams.

Actually the limited number of lanes is what enables us to survive the speed differentials. Fast/[middle/]slow lanes can easily be enumerated without counting, which makes situational awareness so much easier. And you certainly do need a lot of situational awareness. It's a bit like CPU registers vs. an unconstrained stack.

I have only ever seen more than three regular lanes in large metropolitan areas where there is hardly any open road between interchanges and where speed limits are a certainty. I don't know if a single piece of four lane unrestricted driving exists in all of Germany, I would not even be entirely surprised if you could not legally build one.

Anecdote: recently went from Offenburg to Stuttgart and back and could drive a pretty much constant 190~240kph all the way (~1h30) except for a couple sections which were not unlimited. Having to slow down to 190kph isn't quite what I'd call a traffic jam. 300kph is just harder because there's not that many vehicles able to go that fast, so you end up catching up with the "slower" (so to speak) ones, and since vehicles are (supposed to) be electronically limited to 250kph, you're bound to meet some anyway.

It was my impression that vehicles aren't supposed to be able to go faster than the speed rating of their tires. Since 250 km/h is a common speed rating for tires, and higher ratings tend to get expensive fast, German cars are often limited to 250 km/h.

No current Porsches (real ones, not the SUVs) are that slow, and the Porsche tire recommendation guide calls for tires rated for 300 km/h, or "over 300 km/h" (the standardized ratings don't go higher) for all models except the Macan SUV with 18" wheels, for which it recommends 270 km/h.

http://files2.porsche.com/filestore/download/usa/none/porsch...

You can thus see why the index of stock tires always vastly overshoot the top speed of a car, e.g my car gets a Y tyre stock even though its top speed is 245kph, and my ex car has a W rating when the top speed is 210kph.

It's not a good idea to go anywhere near the limit of your tire speed index, nor to go cheap and skimp on the index when buying a replacement tire.

I bet the Macan that gets 18" and the W index is the one with low enough top speeds (below 230kph, that'd be 2.0L four-pot petrol and 3.0L V6 Diesel ones)

EDIT: found a reference again WRT index tests

> Speed ratings are based on laboratory tests where the tire is pressed against a large diameter metal drum to reflect its appropriate load, and run at ever increasing speeds (in 6.2 mph steps in 10 minute increments) until the tire's required speed has been met.

https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=...

Almost every freeway around major American cities is 4 lanes and yet traffic persists. Some freeways in LA are 6 lane parking lots.