
Do drivers who keep gaps in stop-and-go traffic worsen it? (2012) - throwaway000002
https://www.quora.com/Do-drivers-who-keep-extremely-huge-gaps-between-their-car-and-the-car-in-front-of-them-in-heavy-very-slow-stop-and-go-traffic-cause-the-congested-traffic-to-be-worse?share=1
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jameslk
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.

~~~
Retric
Don't forget a reasonable gap can significantly increase your fuel economy and
how long your breaks last. Remember every time you break that's costing you
money.

~~~
mirimir
I have a manual transmission, so it's also clutch wear. Plus I get tired of
shifting.

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legohead
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...

~~~
jameslk
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
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.

~~~
vectorjohn
Hey, if you're being tailgated you're by definition not slower traffic.

Dumb people tailing and trying to go that extra 5mph are as much to blame for
the danger as the people that don't get out of the way. And since they will be
constantly forcing people to switch lanes, the outcome is the same except some
idiot got their way.

So no.

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abdulhaq
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.

~~~
kbenson
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
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
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.

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metanoia
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
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
Though eventually, flat.

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jrs235
An interesting site:
[http://trafficwaves.org/trafexp.html](http://trafficwaves.org/trafexp.html)

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delinka
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
Zipper Merge to the rescue!

[http://www.dot.state.mn.us/zippermerge/](http://www.dot.state.mn.us/zippermerge/)

~~~
jrs235
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.

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sandworm101
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.

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vectorjohn
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
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
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.

~~~
sandworm101
I hope I am not seated in a row behind your's on my next flight. Those at the
front of long lines have a moral obligation to all those behind them. Delaying
hundreds of people for seconds is just as bad as delaying one person for an
hour.

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dynomight
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.

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GhotiFish
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!

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ColinCochrane
Here's some evidence that creating those wide gaps does help.

[http://www.slate.com/articles/life/transport/2011/10/rolling...](http://www.slate.com/articles/life/transport/2011/10/rolling_speed_harmonization_how_colorado_fights_congestion_on_i_.single.html)

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baldfat
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
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.

