4 ms·

I'm not convinced that leaving shorter gaps between cars increases volume. Instead it creates waves of drivers slamming on the brakes because they are unable to

by rlpb 11y ago

I'm not convinced that leaving shorter gaps between cars increases volume. Instead it creates waves of drivers slamming on the brakes because they are unable to react gradually, creating congestion instead. If we all left bigger gaps, we'd all be able to drive faster, increasing throughput (on highways, at least). > Now I wonder if google-driven cars would actually be less efficient for LA. Sure there wouldn't be any traffic-slowing accidents, but there'd be 50% less volume traveling 20mph slower. Self-driving cars in a line could detect and link up with each other, sharing sensor data on obstacles up ahead. In the end, this has the potential to safely reduce the gaps between cars at higher speeds and thus actually increase throughput, since the congestion issues with human drivers reacting separately would not apply.

duaneb 11y ago
> Self-driving cars in a line could detect and link up with each other, sharing sensor data on obstacles up ahead. In the end, this has the potential to safely reduce the gaps between cars at higher speeds and thus actually increase throughput, since the congestion issues with human drivers reacting separately would not apply. Isn't this already true to a certain extent with map software? It automatically directs you to the fastest route—congestion relief is, in a way, built-in to open infrastructure. It seems to be the topology of the highway system would have a much larger impact on congestion than the drivers themselves. Among other things, it's going to be a long time (hopefully never. IMHO) before human drivers are off the road.
- tcdent 11y ago
  In my experience, including such prestigiously congested roadways as the 405, 101 and the 10, it has a lot to do with behavior (ie. the 'caterpillar' effect) than route. Rather, it's not physical space, but delays in processing speed adjustments. Distracted drivers accelerate and brake late, causing complete stops and quick acceleration to catch up.
  - duaneb 11y ago
    Well, I can't speak for LA, but you have to acknowledge the role of having all those drivers on the road in the first place. Distributed better, jitter in driver behavior should tend towards having no effect with the distance between cars.
    - tcdent 11y ago
      Yeah, you're right, physical density does have a role. There's a sort of critical mass that happens; traffic flows well even though everyone is being dumb vs. traffic stopping when everyone is being dumb...
3pt14159 11y ago
This has actually been studied, and it depends on many factors like time of day + sun location, the weather, pavement conditions, and rigour during driver licensing. Optimal flow on a highway during sunshine is around 80km/h, where the gap between the cars is around a car and a half length. Under that and we would be better off having parking lot queues before onramps. So why don't we do this? Because usually people want to travel to the city from the suburbs. The only place that has room to build these parking lots are the suburbs, but then the city couldn't take the excess flow (since it all needs to empty out into city streets and parking lots anyway).

by rlpb 11y ago

duaneb 11y ago

> Self-driving cars in a line could detect and link up with each other, sharing sensor data on obstacles up ahead. In the end, this has the potential to safely reduce the gaps between cars at higher speeds and thus actually increase throughput, since the congestion issues with human drivers reacting separately would not apply. Isn't this already true to a certain extent with map software? It automatically directs you to the fastest route—congestion relief is, in a way, built-in to open infrastructure. It seems to be the topology of the highway system would have a much larger impact on congestion than the drivers themselves. Among other things, it's going to be a long time (hopefully never. IMHO) before human drivers are off the road.

tcdent 11y ago
In my experience, including such prestigiously congested roadways as the 405, 101 and the 10, it has a lot to do with behavior (ie. the 'caterpillar' effect) than route. Rather, it's not physical space, but delays in processing speed adjustments. Distracted drivers accelerate and brake late, causing complete stops and quick acceleration to catch up.
- duaneb 11y ago
  Well, I can't speak for LA, but you have to acknowledge the role of having all those drivers on the road in the first place. Distributed better, jitter in driver behavior should tend towards having no effect with the distance between cars.
  - tcdent 11y ago
    Yeah, you're right, physical density does have a role. There's a sort of critical mass that happens; traffic flows well even though everyone is being dumb vs. traffic stopping when everyone is being dumb...

3pt14159 11y ago

This has actually been studied, and it depends on many factors like time of day + sun location, the weather, pavement conditions, and rigour during driver licensing. Optimal flow on a highway during sunshine is around 80km/h, where the gap between the cars is around a car and a half length. Under that and we would be better off having parking lot queues before onramps. So why don't we do this? Because usually people want to travel to the city from the suburbs. The only place that has room to build these parking lots are the suburbs, but then the city couldn't take the excess flow (since it all needs to empty out into city streets and parking lots anyway).