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What are the differences between the Autobahnen and the Interstate Highway System?
I know there are some Germans on Tildes, figure at least one of y’all might know. How does a typical Autobahn differ from a typical Interstate in design and construction? How often is repair work done and how long does it last? What work would be required to upgrade an Interstate to Autobahn standards?
One Thing I can think of off the cuff is lane width, of all things. German roads have lanes that leave comparatively little space beyond the width of the cars, while I could tell we were close to Ramstein AFB by just the width of lanes.
As for maintenance, most Autobahnen are in good shape, though there's a backlog of deferred maintenance in the form of aging bridges coming in. The government hasn't invested nearly enough into infrastructure the last decades. Individual repair projects can take many years, but they're usually done such as to not disturb traffic: for example, the central divider can be removed in places. You'll often see e.g. northbound and southbound traffic share the northbound side, while the southbound side is being overhauled. Usually, they'll install a temporary divider and set a 80kph speed limit in that case. With what I know of Interstates, with the wide but unprotected divider, having vehicles cross that divider in order to overhaul one side of the highway might not be viable.
They can even do this when replacing (some) bridges, as those bridges are often two identical bridges next to one another. I've previously had the pleasure of regularly seeing such a site, sometimes up close. Traffic was sharing one of the bridges, while the other one was being torn down and replaced.
Don't worry about the lack of speed limit, that's just for maniacs. The de-facto speed limit is often at 130-150kph. Going beyond 180kph is exceptionally rare for almost anyone, most just aren't interested in those speeds. It gets unpleasant and uneconomical.
That said, I don't drive enough, certainly not in the US, to answer this. Maybe it would help if you were to describe the construction features of interstates that you're interested in.
Thanks. What I’ve heard is that Autobahnen are built for faster overall speeds, with gentler curves, longer sightlines, etc. I’m most curious to see what work would need to be done to allow for a given section of Interstate to have an unlimited top speed (obviously not getting into the cultural shifts needed).
Looking at maps of the I-95 in some city areas and A-5 near e.g. Frankfurt, the "gentler curves" might be a thing. German Autobahns tend to avoid densely populated cities as much as possible, so you might see a 30° turn stretched out over 2km or so, while I-95 does 90° turns in less than that, even around similarly sized cities like Baltimore. So the thing about sight lines seems to be a thing. Nevermind that at higher speeds, mechanical factors are also a consideration - most cars aren't built to handle well at high speeds. The steering gets kinda mushy, so tighter turns get unpleasant to drive. Frankly, the tightest turns are maybe found in the mountains/hills. Germany is criss-crossed with low mountain ranges, even in somewhat populated areas, and particularly between those, so often there's no choice but to have highways in there too. There you can see turns comparable to I-95 in cities. Consider for example A-45 between Herborn and Siegen.
I think a lot of this has to do with urban planning and the social/cultural role of cars as well. Germany's major highways were built in the 30s and 40s, when cars weren't ubiquitous. The US Interstate system was built in the 50/60s, when cars were much more ubiquitous, so it was acceptable to put highways very close to city centers. The moment you have to talk about urban planning to upgrade the Interstate system, I think the investment needed defies acceptable limits.
And while I know your question is mostly a hypothetical, allow me to question the question: Germany is currently having the very difficult debate of introducing a general speed limit for the Autobahn system, both in the interest of safety and in the interest of ecological goals. Basically, 130km/h / 80mph would be a reasonable limit. I'm not sure how the situation looks in the US - how far away you are from that goal - but I personally don't see the benefit of going much faster than that. Certainly even under ideal conditions I don't go faster than about 150km/h, and I think most people would like to do that most of the time. If you're going 150km/h, trying to pass someone going 130km/h, having to check your mirrors before entering the left lane is a thing. Having to check them incessantly and anxiously, because someone going 240km/h might be coming up, makes the experience worse for everyone else. And yes, that's a thing, people will come up from behind going highway speeds faster than highway speed. That's intensely unpleasant.
Nevermind that german drivers are (exceptions notwithstanding) highly disciplined. Generally, only passing on the left, while driving as far to the right as possible. This makes highway driving a highly concerted team effort, in a way. I'm not sure you could train US drivers to that standard if you really tried.
For a real-world look at how the above works, maybe have a look at this - don't mind the talking, just a guy trucking around. Observe the behavior of drivers when overtaking for a bit. Unfortunately I can't find a video of everyday daytime driving in dense traffic that isn't deliberately /r/idiotsincars.
They do similar things for maintenance of bridges on Interstates in the US. Instead of two bridges they use one bridge with one lane in either direction, with a temporary divider of concrete blocks.
In rural areas, since the median between lanes in opposite directions is so wide, often with a ditch in the middle, they build up and pave temporary ramps to the other side. Sometimes this is quite far from the bridge.
This is not really relevant to the maintenance , but more an interesting fact.. there are some interstates which reverse the direction of the “fast lane” (one to the left) during peak hours. A temporary separator is raised between the middle and left most lane, and a 3 lane north and 3 lane south highway becomes a (for example) 2 lane north and 4 lane south.
I’ve only seen this in just outside densely populated cities where inbound traffic and outbound traffic change depending on which rush hour it is, morning or evening. This of course is a permanent structure, so it likely has minimal maintenance use, but it seemed relevant enough to share.
I think I've seen this in a short video somewhere. On the Golden Gate Bridge. Oh, here it is. It creates this wonderfully paradoxical effect, where from the perspective of an individual driver, it only adds road space. Like, if you're inbound in that gif, the moment you pass that zipper, it's adding a third lane. And if you're outbound, the moment you pass it, it's adding a fourth lane. Where the fuck did that 7th lane come from?! (/s)
Also, if you're inbound, that thing is (partially) on your side of the divider, on the fast lane, coming towards you. Wat.
You can see from my amazement: We don't have these here.
You know what, that’s even cooler than what I was referring to. I’ve seen these in upstate NY, but never during rush hour, so I have no idea if they actually use them.
Anyways, This is what I was referring to.It’s honestly one of the most unnerving things to experience. But hey, if it gets people where they need to go faster, then so be it. Lol