3 ms·

Traffic is a compression wave. You brake, then the person behind you brakes, then the person behind them, etc. You accelerate, then the person behind you...

Traffic is a compression wave. You brake, then the person behind you brakes, then the person behind them, etc. You accelerate, then the person behind you... Highways that become automated-only will not have this problem. The cars can communicate with each other and change speed in unison. You don't even need to convert a whole highway, you can just reserve a single lane for automated cars and get most of the same benefits.

Johnny555 11y ago
The near gridlock on SOMA streets every rush hour isn't because of a compression wave - there are simply too many people trying to drive out of the city at once. Even if magical cars could erase congestion on freeways, there's still the problem of not enough parking for everyone that would have to drive without public transit. And don't say "But self driving cars will fix everything! They don't even need to park, they can drop you off at work and drive away". If the cars aren't parked, they are contributing to congestion. And since commutes aren't generally balanced, it's not like the self-driving car will leave Walnut Creek at 8am, drop you off in SF at 9am and then pick up a new passenger to head back to the East Bay - that car is going to be loitering around SF somewhere, waiting to take someone back home to the East Bay. SF Muni carries 600,000 passengers/day. BART carries 400K (though not all to SF). Caltrain contributes another 50K. How could you possible accomodate all of these people without transit? Like I said, building effective transit in existing cities is very expensive -- the BART system cost around $1.5B when it was built (around $20B today), but few would argue that SF would be better off without it.
- marcoperaza 11y ago
  >If the cars aren't parked, they are contributing to congestion. And since commutes aren't generally balanced[...] that car is going to be loitering around SF somewhere You're right, traffic patterns are not balanced, so the cars returning to the hot areas for pickups will not be contributing to the traffic in the most-congested direction. Also, SF already has BART, Caltrain, and SF Muni. I'm not familiar with the specific history here, but transit and housing are the limiting factors for where people live in the first place, so the number of commuters will expand when capacity increases. The better question is, what if SF didn't build those systems? It wouldn't be San Francisco today minus the trains, it'd be a totally different San Francisco. So you can't really take the ridership numbers from today as evidence that city couldn't cope without trains. Also, this was all happening when self-driving cars were not around the corner. It's a different story today.
  - Johnny555 11y ago
    >You're right, traffic patterns are not balanced, so the cars returning to the hot areas for pickups will not be contributing to the traffic in the most-congested direction. Except that in a city, all traffic contributes to congestion,there is no single "commute direction". >Also, this was all happening when self-driving cars were not around the corner. It's a different story today. That "corner" is decades away, meanwhile, people need to get to work today -- and you still haven't explained how self-driving cars can replace a million+ trips/day on city streets that are already at capacity during rush hour. They may be self-driving, but they still drive on roads.

Johnny555 11y ago

The near gridlock on SOMA streets every rush hour isn't because of a compression wave - there are simply too many people trying to drive out of the city at once. Even if magical cars could erase congestion on freeways, there's still the problem of not enough parking for everyone that would have to drive without public transit. And don't say "But self driving cars will fix everything! They don't even need to park, they can drop you off at work and drive away". If the cars aren't parked, they are contributing to congestion. And since commutes aren't generally balanced, it's not like the self-driving car will leave Walnut Creek at 8am, drop you off in SF at 9am and then pick up a new passenger to head back to the East Bay - that car is going to be loitering around SF somewhere, waiting to take someone back home to the East Bay. SF Muni carries 600,000 passengers/day. BART carries 400K (though not all to SF). Caltrain contributes another 50K. How could you possible accomodate all of these people without transit? Like I said, building effective transit in existing cities is very expensive -- the BART system cost around $1.5B when it was built (around $20B today), but few would argue that SF would be better off without it.

marcoperaza 11y ago
>If the cars aren't parked, they are contributing to congestion. And since commutes aren't generally balanced[...] that car is going to be loitering around SF somewhere You're right, traffic patterns are not balanced, so the cars returning to the hot areas for pickups will not be contributing to the traffic in the most-congested direction. Also, SF already has BART, Caltrain, and SF Muni. I'm not familiar with the specific history here, but transit and housing are the limiting factors for where people live in the first place, so the number of commuters will expand when capacity increases. The better question is, what if SF didn't build those systems? It wouldn't be San Francisco today minus the trains, it'd be a totally different San Francisco. So you can't really take the ridership numbers from today as evidence that city couldn't cope without trains. Also, this was all happening when self-driving cars were not around the corner. It's a different story today.
- Johnny555 11y ago
  >You're right, traffic patterns are not balanced, so the cars returning to the hot areas for pickups will not be contributing to the traffic in the most-congested direction. Except that in a city, all traffic contributes to congestion,there is no single "commute direction". >Also, this was all happening when self-driving cars were not around the corner. It's a different story today. That "corner" is decades away, meanwhile, people need to get to work today -- and you still haven't explained how self-driving cars can replace a million+ trips/day on city streets that are already at capacity during rush hour. They may be self-driving, but they still drive on roads.