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I find that on my commute most of the time when one lane is moving slow it’s because the vehicle at the front of a long line of cars, usually the left two lanes

I find that on my commute most of the time when one lane is moving slow it’s because the vehicle at the front of a long line of cars, usually the left two lanes, in traveling 5-10 mph slower than other traffic. Speed differential and the use of brakes seems to cause traffic jams, so having vehicles all traveling the same speed or at least moving out of the way if they’d prefer not to go with the flow would seem to solve these issues.

bryanlarsen 8y ago
"A long line of cars ... traveling 5-10 mph slower" In other words you're saying that they're closely packed. If the distance between cars is reduced by 50% and their speed has reduced 10-15%, the throughput of that section of road has increased substantially. As you said, it's speed differential and the use of brakes that causes traffic jams. By that reasoning, the left lane should go the same speed as the right. That would also discourage the use of lane changes which is generally what causes people to use their brakes on the freeway... And remember the square law of braking. Because the safe following distance increases so much when you increase speed, faster speeds on the freeway decrease throughput rather than increase it.
- alphabettsy 8y ago
  No. I’m saying that when faster traffic comes across these drivers they either change lanes immediately, if possible, which causes problems or they stay behind that driver, but still with many cars hunting for a faster moving lane behind them. I don’t find the slow moving line to be any closer together at all mostly because of people constantly changing through that lane. If the far right or middle lanes are traveling faster than the left and also moving smoothly then someone’s doing it wrong.
- Sohcahtoa82 8y ago
  > And remember the square law of braking. Because the safe following distance increases so much when you increase speed, faster speeds on the freeway decrease throughput rather than increase it. Got an article to explain this? It seems counter-intuitive. Following distances should be based on time, not physical distance. It shouldn't matter if cars are going 30 mph or 300 mph. If everyone maintains a 3 second following distance, there should still be a throughput of 20 cars per minute.
  - bryanlarsen 8y ago
    At 10mph, safe following distance is 1.8 seconds. At 60mph, safe following distance is 3.6 seconds. At 90mph, safe following distance is 4.4 seconds. http://www.adventures-in-education.com/math/StoppingDistance.htm http://www.adventures-in-education.com/math/StoppingDistance... https://en.wikipedia.org/wiki/Braking_distance https://en.wikipedia.org/wiki/Braking_distance

bryanlarsen 8y ago

"A long line of cars ... traveling 5-10 mph slower" In other words you're saying that they're closely packed. If the distance between cars is reduced by 50% and their speed has reduced 10-15%, the throughput of that section of road has increased substantially. As you said, it's speed differential and the use of brakes that causes traffic jams. By that reasoning, the left lane should go the same speed as the right. That would also discourage the use of lane changes which is generally what causes people to use their brakes on the freeway... And remember the square law of braking. Because the safe following distance increases so much when you increase speed, faster speeds on the freeway decrease throughput rather than increase it.

alphabettsy 8y ago
No. I’m saying that when faster traffic comes across these drivers they either change lanes immediately, if possible, which causes problems or they stay behind that driver, but still with many cars hunting for a faster moving lane behind them. I don’t find the slow moving line to be any closer together at all mostly because of people constantly changing through that lane. If the far right or middle lanes are traveling faster than the left and also moving smoothly then someone’s doing it wrong.
Sohcahtoa82 8y ago
> And remember the square law of braking. Because the safe following distance increases so much when you increase speed, faster speeds on the freeway decrease throughput rather than increase it. Got an article to explain this? It seems counter-intuitive. Following distances should be based on time, not physical distance. It shouldn't matter if cars are going 30 mph or 300 mph. If everyone maintains a 3 second following distance, there should still be a throughput of 20 cars per minute.
- bryanlarsen 8y ago
  At 10mph, safe following distance is 1.8 seconds. At 60mph, safe following distance is 3.6 seconds. At 90mph, safe following distance is 4.4 seconds. http://www.adventures-in-education.com/math/StoppingDistance.htm http://www.adventures-in-education.com/math/StoppingDistance... https://en.wikipedia.org/wiki/Braking_distance https://en.wikipedia.org/wiki/Braking_distance