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> For city planners, there's a natural hierarchy of roads: limited-access freeways, arterials, collectors, and residential streets No it is not natural. it was

> For city planners, there's a natural hierarchy of roads: limited-access freeways, arterials, collectors, and residential streets No it is not natural. it was invented half a century ago and maybe that hierarchy is a mistake. It creates artificial segregation between places that are geometrically near each other, especially for non-motor modes of transport and for short trips. And it creates natural hub chokepoints at every merge onto a bigger road. I'm a big fan of the Manhattan approach -- just have a big ass grid with much less distinction between so many hierarchies. Bonus points if you make one axis have one ways with "green wave" traffic light timings (this means in low to medium congestion, a driver never hits any red lights! Like a freeway, but mad cheap) The nice thing about a real grid is it is insanely resilient. There is a capacity to absorb a huge amount of thoroighput and route around huge amounts of temporary blockage, even if latency isn't great (at least in a high demand place like Manhattan -- in a more modest town it could make traffic insanely fast if one way green waves are used). Eg If 41st street is blocked, 39th and 43rd work, and if those are clogged, so does 37th and 45th, etc. BTW the fact that there is a linearly increasing cost to using a parallel street is a feature not a bug; it dampens induced demand while still making the capacity available in proportion to its actual demand. Just adding more lanes to a single freeway is not as effective for this reason. I think artificially forcing traffic into scale free graphs with chokepoints every place you switch hierarxhy levels may have been quite a mistake. Those chokepoints are always clogged.

chongli 9y ago
Grids are bad. They encourage traffic. They turn everything into a snarl. Look at Manhattan, it's a disaster! A scale-free network makes through-traffic impossible in residential areas. That is a good thing. People don't want commuters constantly driving by when their kids are out playing. The goal of a road network is to connect everything, not to guarantee a shortest path from every point to every other point.
- ghaff 9y ago
  I'm not sure the grid is the problem. More like the number of vehicles that want to get from point A to point B. Manhattan is indeed horrible to drive in at locations/times when the roads are very congested. But I've also driven in plenty of sparsely-traveled grids where traffic isn't bad at all.
- galdosdi 9y ago
  Manhattan is not a disaster, it's a miracle: 1. except for midtown core, pm rush hour amd near NJ tunnel ramps, during the day cars travel almost as fast as any other mode, despite taking up so much more space than the effecient modes 2. This is perhaps the densest wealthiest place on the planet. The demand for driving is insanely high and tje available supply of space is insanely low. And for some incomprehensible reason there is no limit placed on driving whatsoever. Any yahoo with any car can drive in and out and around manhattan and park anywhere all for free(1). Under these insane conditions you'd expect average speeds to degrade to where walking is faster. Most of thr time kn most of Manhattan this doesn't happen. It's a huge success story. 3. There are better ways to slow down traffic than by preventing thru traffic. Just narrowing the road works wonders. As a pedestrian / cyclist i care about this a lot. There are scary roads in manhattan (eg avenues) but the very narrowest roads that are swingle lane between parked cars prevent a driver from going too fasr for fear of hitting the parked cars. (1) Tolls apply if they enter from NJ, but entering from new England or long island is free.
bogomipz 9y ago
>"I'm a big fan of the Manhattan approach -- just have a big ass grid with much less distinction between so many hierarchies." Most of Los Angeles is laid out in a grid. Just look at a map. Almost the entire LA basin is a grid. The stops at the hills of course but then a grid resume in the valley. Have you been to Manhattan any time recently? Because traffic is really bad. And Manhattan also has a hierarchy. Highways - West Side Highway and the Hudson. Arterials - 42nd, 34th, 23rd 14th. And then smaller residential streets. Also Manhattan is 13 miles long by 2 miles wide. Los Angeles is close to 500 square miles. You can' really compare them.
- galdosdi 9y ago
  Yeah ive been to manhattan, I live drive and bike there. I'm a licensed yellow taxi driver too, though I don't start work till next week. Latency is bad but thoroighput is amazingly good. With the high level of wealth theres no physical way short of congestion charges that manhattan wouldn't be clogged all the time. Tbqh outside of the PM rush,core midtown, and the tunnel ramp areas, I find driving in manhattan during the day to be just fine. You don't go faster than a bicycle, but what do you expect? Thanks to the grid you are still able to make consistent progress toward your destination. When your vehicle size is so inefficiently large in such a dense place, merely matching speed of the effecient modes is a freaking miracle, not a disaster. It's true manhattan has a certain amount if hierarchy but its optional, unlike a classic suburban pattern. You can still take 28th instead of going to 34th or 42nd if you want, and depending on how far you're going this may be faster. You meant FDR and West Side. These are only 6 lanes each and only contribute about as much as an extra avenue each. Can you explain why LA and manhattan size or aspect ratio make them incomparable rather than just hand waving? I've thought a lot about how a green wave system can be applied even in a very square town.
  - bogomipz 9y ago
    >"Latency is bad but thoroighput is amazingly good." No the throughput is most certainly "amazingly good." The number of of avenues and major east-west thoroughfares is small compared to the number of one lane one way street. Throughput is decreased further by the volume construction that happens now, the protected bile line and dedicated bus lanes. >"Can you explain why LA and manhattan size or aspect ratio make them incomparable rather than just hand waving? " There was nothing hand wavy abut anything I wrote. Nor did it concern aspect ratios, there is nothing geometric about the footprint of LA at all. The fact that Los Angeles is such a sprawl means that amount track miles it would now take to provide similar transit coverage isn't feasible. And probably never will be. There will never be a train that takes someone from Northridge to Culver City or from Westwood to Altadena.

chongli 9y ago

Grids are bad. They encourage traffic. They turn everything into a snarl. Look at Manhattan, it's a disaster! A scale-free network makes through-traffic impossible in residential areas. That is a good thing. People don't want commuters constantly driving by when their kids are out playing. The goal of a road network is to connect everything, not to guarantee a shortest path from every point to every other point.

ghaff 9y ago
I'm not sure the grid is the problem. More like the number of vehicles that want to get from point A to point B. Manhattan is indeed horrible to drive in at locations/times when the roads are very congested. But I've also driven in plenty of sparsely-traveled grids where traffic isn't bad at all.
galdosdi 9y ago
Manhattan is not a disaster, it's a miracle: 1. except for midtown core, pm rush hour amd near NJ tunnel ramps, during the day cars travel almost as fast as any other mode, despite taking up so much more space than the effecient modes 2. This is perhaps the densest wealthiest place on the planet. The demand for driving is insanely high and tje available supply of space is insanely low. And for some incomprehensible reason there is no limit placed on driving whatsoever. Any yahoo with any car can drive in and out and around manhattan and park anywhere all for free(1). Under these insane conditions you'd expect average speeds to degrade to where walking is faster. Most of thr time kn most of Manhattan this doesn't happen. It's a huge success story. 3. There are better ways to slow down traffic than by preventing thru traffic. Just narrowing the road works wonders. As a pedestrian / cyclist i care about this a lot. There are scary roads in manhattan (eg avenues) but the very narrowest roads that are swingle lane between parked cars prevent a driver from going too fasr for fear of hitting the parked cars. (1) Tolls apply if they enter from NJ, but entering from new England or long island is free.

bogomipz 9y ago

>"I'm a big fan of the Manhattan approach -- just have a big ass grid with much less distinction between so many hierarchies." Most of Los Angeles is laid out in a grid. Just look at a map. Almost the entire LA basin is a grid. The stops at the hills of course but then a grid resume in the valley. Have you been to Manhattan any time recently? Because traffic is really bad. And Manhattan also has a hierarchy. Highways - West Side Highway and the Hudson. Arterials - 42nd, 34th, 23rd 14th. And then smaller residential streets. Also Manhattan is 13 miles long by 2 miles wide. Los Angeles is close to 500 square miles. You can' really compare them.

galdosdi 9y ago
Yeah ive been to manhattan, I live drive and bike there. I'm a licensed yellow taxi driver too, though I don't start work till next week. Latency is bad but thoroighput is amazingly good. With the high level of wealth theres no physical way short of congestion charges that manhattan wouldn't be clogged all the time. Tbqh outside of the PM rush,core midtown, and the tunnel ramp areas, I find driving in manhattan during the day to be just fine. You don't go faster than a bicycle, but what do you expect? Thanks to the grid you are still able to make consistent progress toward your destination. When your vehicle size is so inefficiently large in such a dense place, merely matching speed of the effecient modes is a freaking miracle, not a disaster. It's true manhattan has a certain amount if hierarchy but its optional, unlike a classic suburban pattern. You can still take 28th instead of going to 34th or 42nd if you want, and depending on how far you're going this may be faster. You meant FDR and West Side. These are only 6 lanes each and only contribute about as much as an extra avenue each. Can you explain why LA and manhattan size or aspect ratio make them incomparable rather than just hand waving? I've thought a lot about how a green wave system can be applied even in a very square town.
- bogomipz 9y ago
  >"Latency is bad but thoroighput is amazingly good." No the throughput is most certainly "amazingly good." The number of of avenues and major east-west thoroughfares is small compared to the number of one lane one way street. Throughput is decreased further by the volume construction that happens now, the protected bile line and dedicated bus lanes. >"Can you explain why LA and manhattan size or aspect ratio make them incomparable rather than just hand waving? " There was nothing hand wavy abut anything I wrote. Nor did it concern aspect ratios, there is nothing geometric about the footprint of LA at all. The fact that Los Angeles is such a sprawl means that amount track miles it would now take to provide similar transit coverage isn't feasible. And probably never will be. There will never be a train that takes someone from Northridge to Culver City or from Westwood to Altadena.