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by foobarian 2840 days ago
This comes up often, but you gotta think about what would happen if everyone suddenly tripled the gap they leave in front of them. The same road surface would suddenly have 1/3 the throughput. I shudder to think what kind of traffic jam / commute time that would lead to at the edges of the road network.

I do appreaciate when people drive densely packed and I try to do the same (up to a safety limit). For merging there are turn signals.
3 comments
tonyarkles 2840 days ago
> The same road surface would suddenly have 1/3 the throughput

At the same velocity. It's quite possible that with the increased gap and increased flow (less stop & go), you could get higher velocity out of it to compensate. Maybe not 3x the velocity, but 2x gap and 2x velocity seems within the realm of possibility (a 60mph road that slows down to 30mph because people are driving stupidly).

Edit: on the low end, this seems quite possible. Increased gaps raising the mean velocity from 5mph to 15 or 20mph.

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tonyarkles 2839 days ago
I'd edit again, but it's too late. This question kept nagging at me. I figured this must be a studied phenomenon.

https://en.wikipedia.org/wiki/Fundamental_diagram_of_traffic...

This is super interesting! As kind of expected, there's a middle zone that balances out density and velocity. In the context of what we were talking about, the fourth "Basic Statement" jumps out at me: "If one of the vehicles brakes in unstable flow regime the flow will collapse."

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saltcured 2838 days ago
The problem is people trying to maintain ANY fixed gap. If they learned to treat the gap as a spring and then use their mind as a damper while still maintaining safety, they can cancel out many of the pathological oscillations and standing waves that disrupt traffic flow. This task is also much easier when people learn to monitor the road further ahead than just the bumper and taillights they are following.

Following too closely removes any margin for error and so requires you to either mimic every change in speed or create dangerous conditions.

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pfultz2 2839 days ago
Higher density may allow for more volume but it can increase viscosity.
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