4 ms·

I've wondered the same thing about the effect of slow-accelerating trucks on stop-and-go bay area freeway traffic during rush hours. I feel that the effects are

I've wondered the same thing about the effect of slow-accelerating trucks on stop-and-go bay area freeway traffic during rush hours. I feel that the effects are fairly non-linear as more of these vehicles are introduced. Some cities in India don't allow heavy vehicle traffic on congested roads during peak commute hours, though I'm not sure if there's been a study of traffic patterns that validates/simulates these scenarios.

briandear 7y ago
Pretty sure Bay Area Traffic is only negligibly affected by big trucks. It’s, in my experience because they have these ridiculous bottleneck merges (a two lane merge, plus that ridiculous diamond lane, merging into a single lane on the destination highway. It’s like a Venturi. Then there are “exit only” signs designating a lane that isn’t exit only. The 101 south just before the 85 has this problem: you think it’s exit only but it isn’t. Just some bad highway design. Also places like the Embarcadero interchange at the 101 in Palo Alto has existing traffic fighting with entering traffic within 200 meters of space. HOV lanes make it even worse because you end up squeezing all the lanes and you create incentives for HOV drivers to merge all the way to the left as quickly as possible which further delays the main lanes since people are getting slowed down from the lane changes. Then, when HOV drivers have to exit, again they have to merge all the way right again. There is a bottleneck squeeze and the lateral squeeze happening as well. Houston traffic by comparison is “bad” but far better than the Silicon Valley version despite Silicon Valley having a smaller population and fewer cars.
- brg 7y ago
  I used to wonder about this often, and many years ago wrote simulations to model traffic. The introduction of connected on/off ramps were the main cause of congestion due to acceleration, merging, etc. Exit before/ merge after we much better than exit after/merge before. SV has many of these congestion building ramp strategies.
koheripbal 7y ago
I think another consequence of that is that collisions have zero cost. Momentum v strength doesn't scale linearly.

briandear 7y ago

Pretty sure Bay Area Traffic is only negligibly affected by big trucks. It’s, in my experience because they have these ridiculous bottleneck merges (a two lane merge, plus that ridiculous diamond lane, merging into a single lane on the destination highway. It’s like a Venturi. Then there are “exit only” signs designating a lane that isn’t exit only. The 101 south just before the 85 has this problem: you think it’s exit only but it isn’t. Just some bad highway design. Also places like the Embarcadero interchange at the 101 in Palo Alto has existing traffic fighting with entering traffic within 200 meters of space. HOV lanes make it even worse because you end up squeezing all the lanes and you create incentives for HOV drivers to merge all the way to the left as quickly as possible which further delays the main lanes since people are getting slowed down from the lane changes. Then, when HOV drivers have to exit, again they have to merge all the way right again. There is a bottleneck squeeze and the lateral squeeze happening as well. Houston traffic by comparison is “bad” but far better than the Silicon Valley version despite Silicon Valley having a smaller population and fewer cars.

brg 7y ago
I used to wonder about this often, and many years ago wrote simulations to model traffic. The introduction of connected on/off ramps were the main cause of congestion due to acceleration, merging, etc. Exit before/ merge after we much better than exit after/merge before. SV has many of these congestion building ramp strategies.

koheripbal 7y ago

I think another consequence of that is that collisions have zero cost. Momentum v strength doesn't scale linearly.