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Comment by mattvot | Hacker News Reader

Can someone explain how the 2+1 lanes work and how they would reduce road deaths?

You may (and physically can) only overtake when there are two lanes going in your direction. The road alternates every couple of km between 1 and 2 lanes in each direction.

I had the same question as the parent comment. Perhaps I still don't understand. Doesn't that just create a bottleneck every couple of km? It seems to me that around here one of the biggest causes of traffic appears to be when ever there is a lane reduction.

I think the theory is that the middle lane is only used for overtaking slower-moving cars. Perhaps the Swedes, like the Germans, practice good lane discipline and stick to the right until they need to overtake.

I think this 2+1 wouldn't work in the US because (in my experience) very few people use the lanes correctly and they just distribute themselves evenly across all lanes, regardless of speed. That strategy does, indeed, lead to bottlenecks when the number of lanes reduces.

This is normal in the US for roads in mountains (going uphill) and it generally works great.

Here in Australia, 2+1 roads aren't very long - they're usually just long enough for a few cars to overtake a slowpoke, then a few kilometers further on you'll get another chance. You can't really cruise double-abreast on these roads, as they're not long enough for that.

Similarly you can't really bottleneck because the only input is a single-lane road - they're not long enough to add anything more than trivial traffic in rural areas.

I had the same thought living near a city. Then I remembered growing up in a rural area, and the amount of traffic the road is made for is key. Many many roads don't have enough traffic to matter, but could significantly benefit from the ability to pass slower traffic

I'm not sure if it's actually a lane reduction, they might have also just added 1 lane to the previously existing 2 lanes.

The big benefit I see is that you're never entering the opposing traffic lane, so head-on collisions are much less likely.

Most inter-city roads in Sweden were 2-lane roads, where to overtake, you needed to swerve into oncoming traffic, 2+1 roads means that even if you're stuck behind an RV or truck, it won't be long before you can safely overtake. At least that's my assumption...

There is a wikipedia entry here: http://en.wikipedia.org/wiki/2+1_road

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