6 ms·

Do drivers who keep gaps in stop-and-go traffic worsen it? (2012)

abdulhaq 11y ago
The question is too vague to give a good brief answer. Narrowing it down, I believe that it is possible for a good driver to reduce the stop-go element of heavy traffic by following the car in front at a judicious (more than average) distance and then braking more slowly than the car in front as the traffic in front is reducing speed. When the traffic in front starts to accelerate again the driver then accelerates more slowly until a sufficient distance is achieved between him and the car in front such that the slower braking technique can be used again as necessary. I know from personal experience that it is possible to reduce the stop-start nature of the traffic in this way.
- quxbar 11y ago
  As you turn the dial of driver response time, you're basically changing the congestion function of the road. Tim Roughgarden has a fantastic book that's very satisfyingly deep, but succinct. https://mitpress.mit.edu/books/selfish-routing-and-price-anarchy https://mitpress.mit.edu/books/selfish-routing-and-price-ana...
- yareally 11y ago
  The other variable to consider is those that decide they'll reach their destination faster by cutting one car in front of you when you are keeping some distance. I see this happen a lot in traffic and sometimes results in nearly having an accident.
- kbenson 11y ago
  As someone who tries to do this whenever possible, it can be largely for naught if cars in the bordering lanes see the gap you've allowed in front and move into it. :/
  - firebones 11y ago
    If you expand the "leave a gap of 2 seconds" rule to instead follow the car in front of you by 3 seconds, then someone cutting in should only require you to add 1.5 seconds of distance to the new, smaller gap. And since the car cutting in will often tailgate the car in front of you, it's often really around 750ms you'd have to bleed off, which shouldn't require much speed change.
    - kbenson 11y ago
      We're not really talking about that, we're talking about stop-and-go traffic, and smoothing out the stop-and-go portion through the use of an expanding and shrinking buffer in front. It will by necessity be larger and smaller at different times. Additionally, when the gap is lessening because the car in front it stopped or at the slowest speed of the variable speed traffic, another vehicle inserting itself into this buffer can make you slow rapidly, thus negating the point of leaving a buffer to smooth out the variable traffic speed.
  - mirimir 11y ago
    Sometimes I also cut off such interlopers. I can accelerate quite rapidly in first. After a while, surrounding drivers learn to respect that space in front of me.
- chm 11y ago
  I used to commute by car for about 40 minutes to an hour each way. I got pretty good at avoiding "stop and go" without leaving too much space between my car and the one before me. Some useful practices I developed: Don't look at the car directly in front of you. Stare through its windshield if possible to get an idea of what the car second in line is doing. If you can't see through the windshield, try looking at its shadow. And if you don't see a shadow, look under the car right in front of you: you should be able to see the first car's lights illuminate the pavement and guess what it's doing. When it's raining, that is especially easy since the pavement is much more reflective. Also set your mirrors in such a way that creates a "single" mirror. Where the proximal end of your left mirror ends, the proximal (left) end of your cabin mirror begins. Where the distal (right) end of your cabin mirror ends, the proximal end of your right exterior mirror begins. This eliminates the need to look behind you every time you want to switch lanes. It doesn't eliminate your blind spot, merely moves it, but that's only a problem if someone is making a 2-lane change. That's usually pretty rare in heavy traffic. Of course, all of these tricks don't work when others drive too erratically. If you don't gauge the distance between you and the vehicle right before you, others will 100% jump at the chance to cut you.
  - mirimir 11y ago
    > Don't look at the car directly in front of you. Stare through its windshield if possible to get an idea of what the car second in line is doing. Yes! Also, when it's darker, you look for brake lights way ahead. That's also a marker for speed traps.
delinka 11y ago
There's always a wide range of gaps in stop-n-go traffic. Anything from a car length to 1,000 feet. It's the 1Kft gappers that seem to bring out the crazy in other drivers. Tangent: how about the drivers that think we should all be merging one entire mile before the merge point and therefore start straddling two lanes in an attempt to prevent passing in the empty lane? We're supposed to use all the pavement and then zipper merge at the merge point. This would be even easier if traffic would be consistent about gaps.
- firebones 11y ago
  Zipper Merge to the rescue! http://www.dot.state.mn.us/zippermerge/ http://www.dot.state.mn.us/zippermerge/
  - jrs235 11y ago
    I wish people would understand the zipper merge and that people shouldn't form a long line since that pushes the congestion further back possibly through intersection and traffic lights causing gridlock which pushes the congestion to streets going perpendicular to the road with the merge. The problem is people think you're "cutting" if you stay in the non-blocked lane up until the merge point and then won't let you in.
jrs235 11y ago
An interesting site: http://trafficwaves.org/trafexp.html http://trafficwaves.org/trafexp.html
baldfat 11y ago
You stay with in 3 seconds so like 25 feet in most traffic NOT 1000 feet!!! It is all about how many cars flow through a certain spot a minute. If you have space you have more time therefore creating MORE traffic behind you! If I had a billion dollars this would be a Super Bowl Commercial and I would blast YouTube and FaceBook with ads.
- abduhl 11y ago
  I'm upvoting you so that others can see an example of incorrect thinking for traffic problems. Throughput is only one goal for traffic. One can see immediately that a minute of flow at 15mph is equivalent to a minute of stop/go traffic at 30mph equally divided. Similarly, a minute of flow at 15mph is less than a minute of stop/go traffic at 45mph. The latter is NOT the goal of a congruent traffic system because it will result in decreased safety. Eliminating gridlock is a priority for all traffic engineers. The more important goal for traffic is safety. It is also immediately evident that constant, predictable traffic patterns result in lower accident rates than unpredictable changes like those found in stop and go traffic. Stop and go traffic encourages tailgating, aggressive lane changing, and aggravated driving. The phrase "you have more space you have more time" does not imply "MORE traffic". It is actually the people driving with this type of mindset that create the traffic, not the person in front.
- jessaustin 11y ago
  If I had a billion dollars I'd hire a driver.
- baldfat 11y ago
  So I got down voted for saying having more space causes more traffic? I really am confused???? So the down votes are for the desire that people INCREASE the distance between them and the car inf ront when the speeds drop?
metanoia 11y ago
When I'm in LA and it's stop-and-go traffic, I find it's best to follow the trucks in the right lane. I average a much higher speed because they don't have the ability to tailgate and slam on their brakes like the most aggressive drivers in the fast lane who are actually causing the traffic jam, and consequently go an even 15 mph as opposed to 0-30-0-30-0, etc.
- mirimir 11y ago
  I strive to maintain a constant speed, so the gap in front naturally gets larger as traffic ahead speeds up. Back in the day, when I was typically in a hurry and driving insanely, I liked large gaps because I could slalom through them at high relative speed. I don't do that anymore. I hate it when bikers blow through at 100 kmph relative speed. But at least they're small. Edit: I also hate it when bicyclists blow through city traffic at 10-20 kmph relative speed. For some reason, I'm more afraid of accidentally hurting them.
  - jackweirdy 11y ago
    Though eventually, flat.
- firebones 11y ago
  This may be due to there being more cars exiting the freeway from the right lane. Also, intuitively, drivers often tend to bear left to get to the "fast" lane, but as they defect to the left lane, it frees up the center lane in a similar fashion as exits free up the right lane. My compromise in a three-lane situation is to always favor the center lane in congested traffic, especially prior to an upcoming exit. If traffic starts to move, I can move left since after the exit, the missing cars will be starting to merge back in (and to the left, negating the advantage of the center). If traffic doesn't move, I tend to just maintain center lane. Impatient, frequent lane changers always add risk to themselves and others because they're bouncing back and forth between left (the fast lane and the way things "should" be to them) and the right (which routinely frees up as people exit). They tend make it to where they're going faster, but I don't necessarily think it is worth the risk.
legohead 11y ago
While most of us academics may be familiar with the problem here, it's moot in the end. No amount of education or public awareness will fix this. Our only hope are self-driving cars or other forms of transportation -- train, hyperloop...
- 0xdeadbeefbabe 11y ago
  Will we see a Ballad of John Henry about the last driver?
- ArkyBeagle 11y ago
  I find that simply following proper protocol in traffic rubs off on other drivers. It seems that way anyway. I don't think it's that hopeless. I think most "public awareness" initiatives are pretty hopeless, but my own experience leads me to think that this is tractable. People can learn new mental cost models. I have personally witnessed the basics of this taught as part of a driver safety course, and most of the people who took the course at least made noises like they were surprised at some of the more intuition-challenging aspects.
- jameslk 11y ago
  My hypothesis is that the problem becomes worse by at least a few other's impatience and greed. There might be some educated individuals on the road who try their best to do what's said to lead to better traffic conditions, but its the few that ruin it in the end. A tragedy of the commons.
  - civilian 11y ago
    No way, the checked-out drivers cause a ton more problems than aggressive drivers. If all drivers properly sorted themselves by desired speed from left to right we'd have much more efficient highways. I'd also make the argument that the people who stubbornly don't get out of the way of tailgaters are at fault for creating slow road conditions, and share the blame for a dangerous driving situation. If someone behind you wants to go faster, get the fuck out of the way. And it's not even my preference-- in WA and OR it's literally the law that slower traffic should move right, but I've never heard of anyone being ticketed for it.
jameslk 11y ago
I used to leave wide gaps, but then I found that market economics started to apply and my gaps were just filled by other drivers looking to arbitrage my attempts at stabilizing the economy. Making matters worse, they would just cut me off when their lane slowed, causing the market to suddenly crash in my lane. So now I leave no gaps.
- skybrian 11y ago
  The key is to be happy that you're helping other people change lanes more easily (often a hard thing to do in traffic). It's not going to make much difference in your arrival time.
  - jameslk 11y ago
    I can't remember the last time I was happy sitting in traffic, or feeling empathetic. If I have to slam on my brakes because others are feeling particularly opportunistic, it will only lead to cynicism.
    - firebones 11y ago
      When I maintain gaps, it's not empathy; at best it is a smug feeling of maintaining a better risk management profile than the person deciding to cut. I long ago gave up viewing driving as an adversarial activity. Slamming on the brakes means I'm not maintaining a safe distance or speed. Any pent up frustration or anger I harbor is reserved for the sap that caused the accident up ahead that slowed everyone down in the first place.
    - nostrademons 11y ago
      For me, it's not empathy. It's gas mileage. I burn a whole lot less gas when I'm coasting in 2nd gear than when I have to come to a dead stop, accelerate, step on the brakes again, etc. I've found that usually people who will cut in front of a gap accelerate pretty quick - after all, they're hopping lanes so they can do that. I rarely need to slow down for them, although occasionally some asshole will misjudge distance & speed.
- 11y ago
ColinCochrane 11y ago
Here's some evidence that creating those wide gaps does help. http://www.slate.com/articles/life/transport/2011/10/rolling_speed_harmonization_how_colorado_fights_congestion_on_i_.single.html http://www.slate.com/articles/life/transport/2011/10/rolling...
sandworm101 11y ago
No. Please leave lots of gaps ... ones just long enough for my motorcycle to sneak into. In all seriousness, in many parts of the world it is natural for two-wheelers to filter past stopped cars to fill every available space in stop and go traffic. Given that bikes fit more people into a given space (pushbikes and motorcycles etc) having the cars leave gaps while stopped can be more efficient. But only where there are enough bikes willing to filter, which is rare in north america. What is really interesting to me is the math behind leaving extra space in moving traffic. I have to cross a major bridge every day (Vancouver, Lions Gate Bridge) which is often only one lane for my direction. A driver leaving 5 or 10 seconds worth of space impacts everyone behind them. 10 seconds x 350 cars means that one person leaving too much of a gap is actually creating an hour's worth of delay.
- vectorjohn 11y ago
  One person leaving too much of a gap doesn't create 10 seconds x 350 cars delay. They add 10 seconds delay. You'd only get that hour if everyone had a 10 second gap. And nobody leaves a 5-10 second gap. That's huge. The DMV recommends something like 2-3 seconds.
  - sandworm101 11y ago
    You missed the point. I didn't mean they delayed any one person by an hour. They are delaying 350 people each by ten seconds ... a cumulative delay of an hour. 10 seconds on a bridge is not unusual. They are normally people looking at the view. The kids around here are taught to "Increase your following distance ... to four seconds in bad weather conditions." In Vancouver, that is a not-small amount of the year. http://www.icbc.com/driver-licensing/Documents/drivers5.pdf http://www.icbc.com/driver-licensing/Documents/drivers5.pdf At 75kph (normal speed on a rushhour bridge) 4 seconds means an 80 meter (90yard) gap. If everyone left such a gap any city would grind to a halt.
    - vectorjohn 11y ago
      I didn't miss the point, I just don't think that's a meaningful number. What's meaningful is total throughput and each individual's time on the road. The 10 second gap doesn't much affect either. Also, presumably they'll close the gap or leave the road at some point, at which time cars could (shouldn't) speed up and save their 8 seconds. But it's that kind of stupidity that causes the traffic waves anyway, to save 8 seconds.
GhotiFish 11y ago
I've had numerous debates about this, I've asked someone who works for my local municipalities traffic office about simulations regarding this (though she didn't have the correct simulators to do it, just for intersections). I know the theory, but people frequently and incorrectly state that emergent traffic jams are proof that leaving large gaps to smooth traffic behind you improves traffic flow. That to me this is an unacceptable leap of logic. Why are their no contrasting simulations showing traffic flow with and without these "smoothing" agents? Creating a simulation that has rolling traffic jams, introduce agents that disperse the traffic jam (can you actually disperse these traffic jams anyway? Again, not demonstrated in the story.) Has throughput increased? It's not a given that it has. My concern is that the people who tried to do what I am saying only achieved negative results, so they did not publish. Regardless of my concerns, I believe this theory might be true. Which is why this is so frustrating!
dynomight 11y ago
I've often thought about traffic flow when stuck in traffic. I'm in favor of a bit of a gap. I'll try to describe it. I'll start with what lead me to my conclusion. At a stop light that has turned green all the cars do not go at once. They all proceed sequentially from first to last. If the line is long enough, and the light short enough, the last car cannot make it through. If all cars were to accelerate at the same time simultaneously like a train then many more cars would make it through the light. Of course this will never happen with human drivers. I believe keeping a reasonable buffer in traffic helps prevent the above situation that I see occur at lights. The delay of this affect is repeated for each and every stop. I think an excessive gap would make the flow worse in the way described in the article. I'm thinking there's a happy medium somewhere. Somewhere between the excessive gap of the one that wants to teach everyone the 'wisdom' of the gap and the hot-heads that want to drive over the person in front.

The question is too vague to give a good brief answer. Narrowing it down, I believe that it is possible for a good driver to reduce the stop-go element of heavy traffic by following the car in front at a judicious (more than average) distance and then braking more slowly than the car in front as the traffic in front is reducing speed. When the traffic in front starts to accelerate again the driver then accelerates more slowly until a sufficient distance is achieved between him and the car in front such that the slower braking technique can be used again as necessary. I know from personal experience that it is possible to reduce the stop-start nature of the traffic in this way.

quxbar 11y ago
As you turn the dial of driver response time, you're basically changing the congestion function of the road. Tim Roughgarden has a fantastic book that's very satisfyingly deep, but succinct. https://mitpress.mit.edu/books/selfish-routing-and-price-anarchy https://mitpress.mit.edu/books/selfish-routing-and-price-ana...
yareally 11y ago
The other variable to consider is those that decide they'll reach their destination faster by cutting one car in front of you when you are keeping some distance. I see this happen a lot in traffic and sometimes results in nearly having an accident.
kbenson 11y ago
As someone who tries to do this whenever possible, it can be largely for naught if cars in the bordering lanes see the gap you've allowed in front and move into it. :/
- firebones 11y ago
  If you expand the "leave a gap of 2 seconds" rule to instead follow the car in front of you by 3 seconds, then someone cutting in should only require you to add 1.5 seconds of distance to the new, smaller gap. And since the car cutting in will often tailgate the car in front of you, it's often really around 750ms you'd have to bleed off, which shouldn't require much speed change.
  - kbenson 11y ago
    We're not really talking about that, we're talking about stop-and-go traffic, and smoothing out the stop-and-go portion through the use of an expanding and shrinking buffer in front. It will by necessity be larger and smaller at different times. Additionally, when the gap is lessening because the car in front it stopped or at the slowest speed of the variable speed traffic, another vehicle inserting itself into this buffer can make you slow rapidly, thus negating the point of leaving a buffer to smooth out the variable traffic speed.
- mirimir 11y ago
  Sometimes I also cut off such interlopers. I can accelerate quite rapidly in first. After a while, surrounding drivers learn to respect that space in front of me.
chm 11y ago
I used to commute by car for about 40 minutes to an hour each way. I got pretty good at avoiding "stop and go" without leaving too much space between my car and the one before me. Some useful practices I developed: Don't look at the car directly in front of you. Stare through its windshield if possible to get an idea of what the car second in line is doing. If you can't see through the windshield, try looking at its shadow. And if you don't see a shadow, look under the car right in front of you: you should be able to see the first car's lights illuminate the pavement and guess what it's doing. When it's raining, that is especially easy since the pavement is much more reflective. Also set your mirrors in such a way that creates a "single" mirror. Where the proximal end of your left mirror ends, the proximal (left) end of your cabin mirror begins. Where the distal (right) end of your cabin mirror ends, the proximal end of your right exterior mirror begins. This eliminates the need to look behind you every time you want to switch lanes. It doesn't eliminate your blind spot, merely moves it, but that's only a problem if someone is making a 2-lane change. That's usually pretty rare in heavy traffic. Of course, all of these tricks don't work when others drive too erratically. If you don't gauge the distance between you and the vehicle right before you, others will 100% jump at the chance to cut you.
- mirimir 11y ago
  > Don't look at the car directly in front of you. Stare through its windshield if possible to get an idea of what the car second in line is doing. Yes! Also, when it's darker, you look for brake lights way ahead. That's also a marker for speed traps.

delinka 11y ago

There's always a wide range of gaps in stop-n-go traffic. Anything from a car length to 1,000 feet. It's the 1Kft gappers that seem to bring out the crazy in other drivers. Tangent: how about the drivers that think we should all be merging one entire mile before the merge point and therefore start straddling two lanes in an attempt to prevent passing in the empty lane? We're supposed to use all the pavement and then zipper merge at the merge point. This would be even easier if traffic would be consistent about gaps.

firebones 11y ago
Zipper Merge to the rescue! http://www.dot.state.mn.us/zippermerge/ http://www.dot.state.mn.us/zippermerge/
- jrs235 11y ago
  I wish people would understand the zipper merge and that people shouldn't form a long line since that pushes the congestion further back possibly through intersection and traffic lights causing gridlock which pushes the congestion to streets going perpendicular to the road with the merge. The problem is people think you're "cutting" if you stay in the non-blocked lane up until the merge point and then won't let you in.

jrs235 11y ago

An interesting site: http://trafficwaves.org/trafexp.html http://trafficwaves.org/trafexp.html

baldfat 11y ago

You stay with in 3 seconds so like 25 feet in most traffic NOT 1000 feet!!! It is all about how many cars flow through a certain spot a minute. If you have space you have more time therefore creating MORE traffic behind you! If I had a billion dollars this would be a Super Bowl Commercial and I would blast YouTube and FaceBook with ads.

abduhl 11y ago
I'm upvoting you so that others can see an example of incorrect thinking for traffic problems. Throughput is only one goal for traffic. One can see immediately that a minute of flow at 15mph is equivalent to a minute of stop/go traffic at 30mph equally divided. Similarly, a minute of flow at 15mph is less than a minute of stop/go traffic at 45mph. The latter is NOT the goal of a congruent traffic system because it will result in decreased safety. Eliminating gridlock is a priority for all traffic engineers. The more important goal for traffic is safety. It is also immediately evident that constant, predictable traffic patterns result in lower accident rates than unpredictable changes like those found in stop and go traffic. Stop and go traffic encourages tailgating, aggressive lane changing, and aggravated driving. The phrase "you have more space you have more time" does not imply "MORE traffic". It is actually the people driving with this type of mindset that create the traffic, not the person in front.
jessaustin 11y ago
If I had a billion dollars I'd hire a driver.
baldfat 11y ago
So I got down voted for saying having more space causes more traffic? I really am confused???? So the down votes are for the desire that people INCREASE the distance between them and the car inf ront when the speeds drop?

metanoia 11y ago

When I'm in LA and it's stop-and-go traffic, I find it's best to follow the trucks in the right lane. I average a much higher speed because they don't have the ability to tailgate and slam on their brakes like the most aggressive drivers in the fast lane who are actually causing the traffic jam, and consequently go an even 15 mph as opposed to 0-30-0-30-0, etc.

mirimir 11y ago
I strive to maintain a constant speed, so the gap in front naturally gets larger as traffic ahead speeds up. Back in the day, when I was typically in a hurry and driving insanely, I liked large gaps because I could slalom through them at high relative speed. I don't do that anymore. I hate it when bikers blow through at 100 kmph relative speed. But at least they're small. Edit: I also hate it when bicyclists blow through city traffic at 10-20 kmph relative speed. For some reason, I'm more afraid of accidentally hurting them.
- jackweirdy 11y ago
  Though eventually, flat.
firebones 11y ago
This may be due to there being more cars exiting the freeway from the right lane. Also, intuitively, drivers often tend to bear left to get to the "fast" lane, but as they defect to the left lane, it frees up the center lane in a similar fashion as exits free up the right lane. My compromise in a three-lane situation is to always favor the center lane in congested traffic, especially prior to an upcoming exit. If traffic starts to move, I can move left since after the exit, the missing cars will be starting to merge back in (and to the left, negating the advantage of the center). If traffic doesn't move, I tend to just maintain center lane. Impatient, frequent lane changers always add risk to themselves and others because they're bouncing back and forth between left (the fast lane and the way things "should" be to them) and the right (which routinely frees up as people exit). They tend make it to where they're going faster, but I don't necessarily think it is worth the risk.

legohead 11y ago

While most of us academics may be familiar with the problem here, it's moot in the end. No amount of education or public awareness will fix this. Our only hope are self-driving cars or other forms of transportation -- train, hyperloop...

0xdeadbeefbabe 11y ago
Will we see a Ballad of John Henry about the last driver?
ArkyBeagle 11y ago
I find that simply following proper protocol in traffic rubs off on other drivers. It seems that way anyway. I don't think it's that hopeless. I think most "public awareness" initiatives are pretty hopeless, but my own experience leads me to think that this is tractable. People can learn new mental cost models. I have personally witnessed the basics of this taught as part of a driver safety course, and most of the people who took the course at least made noises like they were surprised at some of the more intuition-challenging aspects.
jameslk 11y ago
My hypothesis is that the problem becomes worse by at least a few other's impatience and greed. There might be some educated individuals on the road who try their best to do what's said to lead to better traffic conditions, but its the few that ruin it in the end. A tragedy of the commons.
- civilian 11y ago
  No way, the checked-out drivers cause a ton more problems than aggressive drivers. If all drivers properly sorted themselves by desired speed from left to right we'd have much more efficient highways. I'd also make the argument that the people who stubbornly don't get out of the way of tailgaters are at fault for creating slow road conditions, and share the blame for a dangerous driving situation. If someone behind you wants to go faster, get the fuck out of the way. And it's not even my preference-- in WA and OR it's literally the law that slower traffic should move right, but I've never heard of anyone being ticketed for it.

jameslk 11y ago

I used to leave wide gaps, but then I found that market economics started to apply and my gaps were just filled by other drivers looking to arbitrage my attempts at stabilizing the economy. Making matters worse, they would just cut me off when their lane slowed, causing the market to suddenly crash in my lane. So now I leave no gaps.

skybrian 11y ago
The key is to be happy that you're helping other people change lanes more easily (often a hard thing to do in traffic). It's not going to make much difference in your arrival time.
- jameslk 11y ago
  I can't remember the last time I was happy sitting in traffic, or feeling empathetic. If I have to slam on my brakes because others are feeling particularly opportunistic, it will only lead to cynicism.
  - firebones 11y ago
    When I maintain gaps, it's not empathy; at best it is a smug feeling of maintaining a better risk management profile than the person deciding to cut. I long ago gave up viewing driving as an adversarial activity. Slamming on the brakes means I'm not maintaining a safe distance or speed. Any pent up frustration or anger I harbor is reserved for the sap that caused the accident up ahead that slowed everyone down in the first place.
  - nostrademons 11y ago
    For me, it's not empathy. It's gas mileage. I burn a whole lot less gas when I'm coasting in 2nd gear than when I have to come to a dead stop, accelerate, step on the brakes again, etc. I've found that usually people who will cut in front of a gap accelerate pretty quick - after all, they're hopping lanes so they can do that. I rarely need to slow down for them, although occasionally some asshole will misjudge distance & speed.
11y ago

ColinCochrane 11y ago

Here's some evidence that creating those wide gaps does help. http://www.slate.com/articles/life/transport/2011/10/rolling_speed_harmonization_how_colorado_fights_congestion_on_i_.single.html http://www.slate.com/articles/life/transport/2011/10/rolling...

sandworm101 11y ago

No. Please leave lots of gaps ... ones just long enough for my motorcycle to sneak into. In all seriousness, in many parts of the world it is natural for two-wheelers to filter past stopped cars to fill every available space in stop and go traffic. Given that bikes fit more people into a given space (pushbikes and motorcycles etc) having the cars leave gaps while stopped can be more efficient. But only where there are enough bikes willing to filter, which is rare in north america. What is really interesting to me is the math behind leaving extra space in moving traffic. I have to cross a major bridge every day (Vancouver, Lions Gate Bridge) which is often only one lane for my direction. A driver leaving 5 or 10 seconds worth of space impacts everyone behind them. 10 seconds x 350 cars means that one person leaving too much of a gap is actually creating an hour's worth of delay.

vectorjohn 11y ago
One person leaving too much of a gap doesn't create 10 seconds x 350 cars delay. They add 10 seconds delay. You'd only get that hour if everyone had a 10 second gap. And nobody leaves a 5-10 second gap. That's huge. The DMV recommends something like 2-3 seconds.
- sandworm101 11y ago
  You missed the point. I didn't mean they delayed any one person by an hour. They are delaying 350 people each by ten seconds ... a cumulative delay of an hour. 10 seconds on a bridge is not unusual. They are normally people looking at the view. The kids around here are taught to "Increase your following distance ... to four seconds in bad weather conditions." In Vancouver, that is a not-small amount of the year. http://www.icbc.com/driver-licensing/Documents/drivers5.pdf http://www.icbc.com/driver-licensing/Documents/drivers5.pdf At 75kph (normal speed on a rushhour bridge) 4 seconds means an 80 meter (90yard) gap. If everyone left such a gap any city would grind to a halt.
  - vectorjohn 11y ago
    I didn't miss the point, I just don't think that's a meaningful number. What's meaningful is total throughput and each individual's time on the road. The 10 second gap doesn't much affect either. Also, presumably they'll close the gap or leave the road at some point, at which time cars could (shouldn't) speed up and save their 8 seconds. But it's that kind of stupidity that causes the traffic waves anyway, to save 8 seconds.

GhotiFish 11y ago

I've had numerous debates about this, I've asked someone who works for my local municipalities traffic office about simulations regarding this (though she didn't have the correct simulators to do it, just for intersections). I know the theory, but people frequently and incorrectly state that emergent traffic jams are proof that leaving large gaps to smooth traffic behind you improves traffic flow. That to me this is an unacceptable leap of logic. Why are their no contrasting simulations showing traffic flow with and without these "smoothing" agents? Creating a simulation that has rolling traffic jams, introduce agents that disperse the traffic jam (can you actually disperse these traffic jams anyway? Again, not demonstrated in the story.) Has throughput increased? It's not a given that it has. My concern is that the people who tried to do what I am saying only achieved negative results, so they did not publish. Regardless of my concerns, I believe this theory might be true. Which is why this is so frustrating!

dynomight 11y ago

I've often thought about traffic flow when stuck in traffic. I'm in favor of a bit of a gap. I'll try to describe it. I'll start with what lead me to my conclusion. At a stop light that has turned green all the cars do not go at once. They all proceed sequentially from first to last. If the line is long enough, and the light short enough, the last car cannot make it through. If all cars were to accelerate at the same time simultaneously like a train then many more cars would make it through the light. Of course this will never happen with human drivers. I believe keeping a reasonable buffer in traffic helps prevent the above situation that I see occur at lights. The delay of this affect is repeated for each and every stop. I think an excessive gap would make the flow worse in the way described in the article. I'm thinking there's a happy medium somewhere. Somewhere between the excessive gap of the one that wants to teach everyone the 'wisdom' of the gap and the hot-heads that want to drive over the person in front.