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Comment by DanielN | Hacker News Reader

I've tried this in Boston. Mass-holes will not stand for you to screw with their traffic jams.

I agree that this doesn't work well around Boston. My opinion is that the fluidity of traffic, ie. lane changing, doesn't break down at low speeds in Boston. If you let a cars length open in front of you it will fill up with a car. I tend to think that this makes efficient use of the pavement available and tends for a traffic flow that is as maximal as possible but I don't have any evidence about that.

If efficient use of pavement means park the most cars on it Then by all means fill every available space. Safe following distance increases with the square of the speed so higher average vehicle speeds means the road carries less traffic. The road moves the most cars around 30mph, so if traffic slows below 30 it will crash to 0mph

Cool! What is the science backing this? Is it coming out of studies or some theoretical modeling? I've been wondering what the most efficient speed for moving traffic was on a typical highway for a while.

Google on "Fundamental diagram" of traffic, or http://en.wikipedia.org/wiki/Fundamental_diagram_of_traffic_... It's a set of graphs. Density plotted against speed, etc. It's old stuff, empirically derived. As flowing cars slowly get closer together on average, drivers slow down a bit for safety, yet with more cars passing per second, so the flow increases. But then as they approach even closer, drivers must greatly slow down because of reaction time issues, even though more cars are packed onto the roads ...and so the slowing dominates the extra cars per mile, and average flow decreases. The peak flow ends up being 30MPH - 40MPH. That flow will most rapidly drain out the backups. I hear that it's a different value in different countries.

But worse is the problem that once everyone slows past the 35MPH hump, traffic becomes unstable, and you get oscillations or standing waves which slow things far more than you might expect.

Rule of thumb (but I've never seen it stated anywhere) 35MPH=51FPS, 3 seconds between cars, gives 150 FEET BETWEEN CARS. Closing up gaps will wreck the max. flow pattern. During congestion, if you start trying to stop others from "cutting you off" or merging ahead, then you're the one causing the jam. (Or to be fair, 30MPH and 2sec gives 90ft spacing, perhaps the bare min.)

Another issue: in 1998 Helbing and Huberman discovered the existence of distinct 'phases' in simulated multi-lane traffic. When all lanes seem to lock together like a moving crystal, that's now called "Synchronous Flow," and gives maximum throughput. But it's on the edge of collapse, and "condensations" are triggered by anyone who tries outrunning neighbors by switching lanes, or who approaches too close and has to tap the brakes. http://www.nature.com/nature/journal/v396/n6713/abs/396738a0...

When I don't know anything about a topic I have found Wikipedia is a good place to start

http://en.wikipedia.org/wiki/Traffic_flow

I've tried this in Phoenix with some success. You do get people passing you, but this helps traffic on average. We also have lights at the freeway on ramps which smooth oncoming traffic, but people ignore them until a line forms. I almost got rear-ended once because someone intended to ignore it and I chose to obey it.

If you do this when traffic is not quite jammed, people are far more upset. It's best used when traffic is being forced to actually stop regularly. You will still get people to honk at you and whatnot, especially once a person or two passes you, but I've long since given up expecting most people to understand the things I do.

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