3 ms·

The claim seems reasonable. Most of the time infrastructure is fine, but that 20% of the time between 4pm and 6pm when you are actually using it, it often is no

The claim seems reasonable. Most of the time infrastructure is fine, but that 20% of the time between 4pm and 6pm when you are actually using it, it often is not. More following distance => less throughput. There is already a math problem at play for how to get millions of single occupancy to and from a given location in a day. Which is to say, gridlock occurs today - it is a fact. Increasing following distance by 2 to 5x would potentially be quite bad for otherwise heavy but flowing traffic. Eg: NYC, it is known for good throughput. Light turns green, everyone picks up speed and keeps tight following distances. Anything less and that city would lock up more so than it already does. Part of the issue is just complexity and variety. 2x following distances on most highways would likely be only a good thing. But in each and every circumstance, not necessarily good, perhaps disaster.

dcow 3y ago
There is pretty well established modeling that demonstrates that the stop and go rhythm that arises from tight following distances leads to worse throughput. To avoid slinking, everyone needs to accelerate and decelerate at the same rate. A safe stopping distance is the only way build in the micro buffers needed to achieve relatively consistent speed at human scale, or without large scale traffic orchestration. The naïve takes just sound like armchair hand waving. I guess that’s what I’m responding to.
- seadan83 3y ago
  It does seem on the road that many people lose the ability to predict 30 seconds in the future. That car in front of you has 10 feet to move? GO GO GO! Wait, it only moved just 10 feet - BRAKE BRAKE BRAKE! I think it can fun to be the driver that smooths out the shock waves, so I do largely agree with your point. Though, all things being equal, double following distance and that will double the length of a traffic jam. Longer traffic jams are more impactful - it takes longer to get through them & the longer traffic jam distance is more likely to cause back-ups on on-ramps and in turn to the surface streets leading to those on-ramps. Which is to say, a higher prevalence of grid-lock. The AI crowd is right to say that with 100% AI cars, you can have smooth and fast traffic with impossibly tight following distances. I do believe you need some impractical necessities to accomplish that though.

dcow 3y ago

There is pretty well established modeling that demonstrates that the stop and go rhythm that arises from tight following distances leads to worse throughput. To avoid slinking, everyone needs to accelerate and decelerate at the same rate. A safe stopping distance is the only way build in the micro buffers needed to achieve relatively consistent speed at human scale, or without large scale traffic orchestration. The naïve takes just sound like armchair hand waving. I guess that’s what I’m responding to.

seadan83 3y ago
It does seem on the road that many people lose the ability to predict 30 seconds in the future. That car in front of you has 10 feet to move? GO GO GO! Wait, it only moved just 10 feet - BRAKE BRAKE BRAKE! I think it can fun to be the driver that smooths out the shock waves, so I do largely agree with your point. Though, all things being equal, double following distance and that will double the length of a traffic jam. Longer traffic jams are more impactful - it takes longer to get through them & the longer traffic jam distance is more likely to cause back-ups on on-ramps and in turn to the surface streets leading to those on-ramps. Which is to say, a higher prevalence of grid-lock. The AI crowd is right to say that with 100% AI cars, you can have smooth and fast traffic with impossibly tight following distances. I do believe you need some impractical necessities to accomplish that though.