[MartinTheK (OP)]

I drive at the speed limit on cruise control.

Obviously I get passed a lot, but I notice that traffic goes by in clumps. Is there some theoretical reason (maybe someting involving entropy?) for this behavior? It is clearly unsafe to exced the speed limit by bunching up like that - even in fog.

[Bored chemist]

The soimple reason traffic gets bunched up is that it's often difficult (or ot doesn't seem worthwhile) to overtake.

[techmind]

If one driver chooses to go slightly slower than the car in front then the gap simply widens, but if his preferred speed is slightly greater than the car in front he will catch up with the car in front and, if it's not practical/worthwhile/too close to the speed limit to overtake, a clump begins to form.

See the very wonderful
 http://trafficwaves.org/
for more related information on applied traffic theory.

I try to be a jam-busting, fuel-economising, calming influence when I'm on the road [8D]

[Don_1]

Drivers who, for reasons best known to themselves, refuse to use the nearside lane prevent faster drivers from overtaking, so you get a long line of vehicles stuck behind. This is particularly the case for trucks over 7.5 ton, which are barred from the offside lane and can't get passed some silly sod who is doing less than 55mph in the center lane.

[lyner]

D1, you're such a boy racer. Just ease up and turn on the radio. Just don't get cross.

The scary thing about these bunching waves is that the back of a queue travels backwards at a fantastic rate. The people at the back of the queue may need to apply their brakes extremely quickly to avoid piling into the guy in front. These new fangled elevated brake lights are a real godsend under those conditions. It needn't be too much of a surprise when the guy in front slows down sharply when you can see three or four cars ahead applying their brakes.

[Don_1]

D1, you're such a boy racer.

BOY!!!! Crumbs, me a boy!!! Thank you. I shall print this out and show others that I am a BOY, Not a old git.

[lyner]

Boy racing is a state of mind - not chronological phenomenon, dear boy!

[rosy]

Drivers who, for reasons best known to themselves, refuse to use the nearside lane prevent faster drivers from overtaking, so you get a long line of vehicles stuck behind. This is particularly the case for trucks over 7.5 ton, which are barred from the offside lane and can't get passed some silly sod who is doing less than 55mph in the center lane.

Of course, you get the same effect with the sort of twerps who think they have a god-given right to do 85 mph (that's 15 mph above the legal limit, for those not based in the UK) all the way from Cambridge to London and come roaring up behind those of us doing 68 mph whilst overtaking a lorry flashing their headlights, and who expect us to undertake a merge/remerge manoeuver to let them past even when there's barely space between two consecutive slow-moving vehicles to fit a car into.
They tend to be the same people who pull into the nearside lane for about a microsecond between two obviously consecutive overtaking manoeuvers even when there is no traffic behind them and no reason to do so. They also brake down to about 52 at the least sign of a speed enforcement camera, endangering those of us rolling along at legal speeds by suddenly coming to a virtual stop infront of us.
Amusingly, these are also typically the same people who complain about the "crippling cost" of fuel taxes... someone really should let them into the whole thing about air resistance, poor lambs.

[turnipsock]

When one lorry overtakes another lorry it's like a rolling road block on the two 'slower' lanes. Its caused be various tolerances in lorry speed limiters and some lorries limited to 54mph and some to 56mph.

The net result is that all the cars have to move to the outside lane. What Rosy says is true, people do get annoyed at people sitting at 68 mph but its because there is a huge line of traffic.

It gets to the point where people start driving up the middle lane and undertaking everybody, then cutting out forcing people in the outside lane to brake, that car behind brakes a little more and then you get a domino effect that can end up in the outside lane being stationary for a second or two.

I have found the best way to combat this is to get alongside the two lorries and the match their speed, allowing the road to clear in front. When the lorry in the middle is clear just accelerate hard and move to the middle or nearside lane.

Repeat this manouver a few times and the jams will be behind you. Just don't stop for your tea or you'll come out into a huge jam.

[DoctorBeaver]

Middle lane hoggers are a menace. I remember 1 particular occasion when I was driving from London to Cambridge (yes,Rosy - the M11 again!) at around 3am. There was no traffic at all and suddenly, there in front of me, was a car in the middle lane. I was doing about 75-80mph at the time (yeah, I know) and caught the car up so fast it couldn't have been doing more than 55-60mph. I had to change from the nearside lane to the outside lane & back again to get past.

But, back to the topic. What Turnipjock said is absolutely right. People pulling into the outside lane and forcing others to brake is a major cause of bunching.

Whilst I agree with Rosy's point about people driving at 85mph, I have often been forced to drive at speeds up to 90mph in the outside lane because that seems to be the average speed. I don't want to be stuck behind 60mph middle lane hoggers or lorries that take 5 miles to overtake other lorries. On more than 1 occasion I've been forced up to almost 100mph to get into the outside lane to overtake (that seems particularly the case on the M1).

[dentstudent]

I was forced to do 130mph on Saturday. Ahhhh! Empty autobahns!

[DoctorBeaver]

I was forced to do 130mph on Saturday. Ahhhh! Empty autobahns!

Oh I know. They're such a trial.

[turnipsock]

I came up the M6/M74 on Sunday night, starting at Stratford Upon Avon at 0015.

I was thinking, while on the M6, there isn't a straight section on the M6 so I was switching from lane to lane in order to get the shortest line but I was still coming across people who just sat in the middle lane. It was one of my better ideas, switching lanes, as it stopped me falling asleep. I could also see which way the road was going to go with the satnav.

There was one point, on the M74, where I was slowing closing on a middle lane driver. I was on the inside lane and thought she would move over as I approached...but she didn't move. I made a big deal of going to the outside lane and then back to the nearside to pass her. She never moved out of the middle lane, I guess she was planing on doing the whole journey in the middle lane or something.

dent, I get a lot of wind noise from the sunroof at anything over 130mph...how do you get around that?

[MartinTheK (OP)]

interesting  comments.

I have a modest proposal to alleviate the California budget deficit which is currently heading north of 20 bevabucks.

If the safe drivers were deputized as the state traffic posse comitatus and equipped with dashboard cameras AND the law was tweaked to make it illegal to  own a car exceeding the speed limit ...

Then the people speeding past them could be mined as a good source of state revenue.

On the drive home from San Francisco last weekend I could have generated $100,000 easily.

[Don_1]

dent, I get a lot of wind noise from the sunroof at anything over 130mph...how do you get around that?

Might one suggest sticking to the 70mph speed limit!

..... make it illegal to  own a car exceeding the speed limit ...

Which speed limit? town, urban or motorway/autoroute/autobahn/freeway?

If the safe drivers were deputized as the state traffic posse .....

..... those who dislike them would run them off the road, shoot them and torch their car.

I think there is enough 'road rage' as it is and the US position regarding guns would make matters 100 x's worse.

Then the people speeding past them could be mined as a good source of state revenue.

On the drive home from San Francisco last weekend I could have generated $100,000 easily.

In the UK drivers are already clobbered with fines for driving, parking, farting and just about everything else.

[dentstudent]

dent, I get a lot of wind noise from the sunroof at anything over 130mph...how do you get around that?

That's EASY! I don't have a sunroof...

[MartinTheK (OP)]

It's already possibly worth your life to stick your tongue out at other drivers in California.

We can make the dash cams very inconspicuous and if 2 % of the cars on the road are possee members...

I don't know about UK drivers, but anybody in an SUV in California is obviously a rich class traitor who deserves to be clobbered by taxes for the common good.

NB Gas in California is currently about $2.50 when it was over $4.00 they would slow down to a slight degree. At $24.50 a gallon -- madness takes control.

How about this - scratch the posse idea. Let's issue letter's of marque band pay 5% of the fines recovered to the road privateers.

Arrrh, me hearties! Were out for gold, so we are -- even though it looks like were innocentlyyoff to the market.

[lyner]

People are obsessed with going fast!
The problem is that people CHOOSE a lifestyle which involves longer journeys than are good for them. It's a vicious circle based on peer pressure and the consumer society. I know that many people feel that they have no option but many of them, if fact, do have a choice.
If it really is as upsetting as they make it out to be, then they should consider a different choice of workplace / living place / holiday destination and reap the benefit.
I expect strong replies from a few who claim to have no choice but . . . .

[turnipsock]

When I was driving back from London to Glasgow, for work, I spotted several middle lane hoggers.




Like this guy.

[dentstudent]

When I was driving back from London to Glasgow, for work, I spotted several middle lane hoggers.

Clumping not too much of a problem, there though, eh? []