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To help pay for tuition, one summer I drove a university shuttle in the evenings after finishing my work-study job. At that time, the lights on Walnut and Chest

To help pay for tuition, one summer I drove a university shuttle in the evenings after finishing my work-study job. At that time, the lights on Walnut and Chestnut streets in West Philly were set up with green waves. The best place to ride the wave was obviously at its tail, entering each intersection a little before the light would turn yellow. Traffic there was light-to-none, and its flow far smoother and safer than at the front, where there were usually drivers pointlessly fighting to maintain their positions. I would watch them all just up ahead of me, wastefully approaching each red light far too fast, braking hard until it turned green, then rapidly accelerating to the next, repeating this insane processes intersection after intersection for a dozen blocks at a time, like some sort of mobile psychology experiment gone wrong. Because I was naive, I thought poorly of Pennsylvania drivers. Later I moved to SF and experienced the same thing on Franklin and Gough, and realized the phenomenon was probably fairly universal. Green Waves could be a great thing, but there's still the unsolved problem of human beings behind the wheel.

maest 7y ago
I think this phenomenon shows the importance of communicating to the drivers that a green wave system is in effect. You can't really fault people for driving myopically if they don't have high level information.
- gwbas1c 7y ago
  Agreed, I once had to tell an out of towner "just drive the speed limit, you'll get all green lights."
  - ttymck 7y ago
    I've noticed (because I once read somewhere) that driving 5-10mph _over_ the limit results in the best timing. This is in both Pennsylvania and Los Angeles.
    - cuddlybacon 7y ago
      At one time a particular subreddit* was quite insistent that it is always the case that going the speed limit always results in the same commute time as speeding. No matter the city. I tried it in Vancouver, and my commute went from 45 mins to 65. The bulk of traffic does 5-10km/h over the limit, so perhaps traffic light timing is based on that. * Reddit is blocked at work, but it was probably something like r/townplanning
    - gwbas1c 7y ago
      The speed varies based on who's timing the lights.
- alamortsubite 7y ago
  That might work, though few drivers in the U.S. heed speed limits even in construction and school zones, where there are typically large brightly-colored signs and flashing lights and the stakes are much higher. Also, since the bad behavior on display at the front of a green wave is pervasive in pretty much all traffic scenarios, it seems like a modicum of driver training might ultimately be the most foolproof approach.
  - maest 7y ago
    With the risk of sounding cynical, I think drivers will be much more receptive to being told "you can get home faster if you follow the rules" than being told "you're increasing the risk of getting into an acceident if you don't follow the rules"
  - dsfyu404ed 7y ago
    >That might work, though few drivers in the U.S. heed speed limits even in construction and school zones, Because there's nothing in it for them. Most school zones don't have kids anywhere nearby outside two specific times of day. Most construction zones don't actually have construction happen. Many posted speed limits are either artificially low by statute (state laws to the tune of "if road has X then max speed limit = Y" are common), for revenue purposes or to account for a temporary condition that does not affect the entire area where the speed limit applies (e.g. a single tight curve or trucks enter/exiting during business hours). In light of these it's no wonder so many drivers disregard posted limits since it allows them to get to their destination faster. If drivers knew that a particular travel speed would result in hitting all greens then you can bet your ass the majority of them would drive that speed. There's a ton in it for them.
aidenn0 7y ago
Where I am there is the problem that in any more than the lightest amount of traffic, the cars queued up at a red take too long to get up to speed, so you end up getting only 2-3 intersections of green before stopping because you never reach the speed-limit. Even when cars do get up to speed, there's things like turning traffic vs. pedestrians. I suppose if they eliminated on-street parking and had dedicated turn lanes for both directions, it would work, but that's not happening any time soon. I can actually make it down the entire length of a 1-way by going 25mph (the speed limit) and weaving between cars like a maniac, but that seems rather unsafe (not to mention illegal).
1123581321 7y ago
There were people in your wave who would have slowed down too much if those cars running ahead were in the pack.
cryptonector 7y ago
> ..., wastefully approaching each red light far too fast, ... Oh, you want to save gas? Joke's on you: > In the UK, in 2009, it was revealed that the Department for Transport had previously discouraged green waves as they reduced fuel usage, and thus less revenue was raised from fuel taxes.

maest 7y ago

I think this phenomenon shows the importance of communicating to the drivers that a green wave system is in effect. You can't really fault people for driving myopically if they don't have high level information.

gwbas1c 7y ago
Agreed, I once had to tell an out of towner "just drive the speed limit, you'll get all green lights."
- ttymck 7y ago
  I've noticed (because I once read somewhere) that driving 5-10mph _over_ the limit results in the best timing. This is in both Pennsylvania and Los Angeles.
  - cuddlybacon 7y ago
    At one time a particular subreddit* was quite insistent that it is always the case that going the speed limit always results in the same commute time as speeding. No matter the city. I tried it in Vancouver, and my commute went from 45 mins to 65. The bulk of traffic does 5-10km/h over the limit, so perhaps traffic light timing is based on that. * Reddit is blocked at work, but it was probably something like r/townplanning
  - gwbas1c 7y ago
    The speed varies based on who's timing the lights.
alamortsubite 7y ago
That might work, though few drivers in the U.S. heed speed limits even in construction and school zones, where there are typically large brightly-colored signs and flashing lights and the stakes are much higher. Also, since the bad behavior on display at the front of a green wave is pervasive in pretty much all traffic scenarios, it seems like a modicum of driver training might ultimately be the most foolproof approach.
- maest 7y ago
  With the risk of sounding cynical, I think drivers will be much more receptive to being told "you can get home faster if you follow the rules" than being told "you're increasing the risk of getting into an acceident if you don't follow the rules"
- dsfyu404ed 7y ago
  >That might work, though few drivers in the U.S. heed speed limits even in construction and school zones, Because there's nothing in it for them. Most school zones don't have kids anywhere nearby outside two specific times of day. Most construction zones don't actually have construction happen. Many posted speed limits are either artificially low by statute (state laws to the tune of "if road has X then max speed limit = Y" are common), for revenue purposes or to account for a temporary condition that does not affect the entire area where the speed limit applies (e.g. a single tight curve or trucks enter/exiting during business hours). In light of these it's no wonder so many drivers disregard posted limits since it allows them to get to their destination faster. If drivers knew that a particular travel speed would result in hitting all greens then you can bet your ass the majority of them would drive that speed. There's a ton in it for them.

aidenn0 7y ago

Where I am there is the problem that in any more than the lightest amount of traffic, the cars queued up at a red take too long to get up to speed, so you end up getting only 2-3 intersections of green before stopping because you never reach the speed-limit. Even when cars do get up to speed, there's things like turning traffic vs. pedestrians. I suppose if they eliminated on-street parking and had dedicated turn lanes for both directions, it would work, but that's not happening any time soon. I can actually make it down the entire length of a 1-way by going 25mph (the speed limit) and weaving between cars like a maniac, but that seems rather unsafe (not to mention illegal).

1123581321 7y ago

There were people in your wave who would have slowed down too much if those cars running ahead were in the pack.

cryptonector 7y ago

> ..., wastefully approaching each red light far too fast, ... Oh, you want to save gas? Joke's on you: > In the UK, in 2009, it was revealed that the Department for Transport had previously discouraged green waves as they reduced fuel usage, and thus less revenue was raised from fuel taxes.