Disco

Speed limits of 50mph may be imposed on sections of some motorways under proposals said to be under consideration by the Government.
The measure is being examined by the Department of Transport, Local Government and the Regions (DTLR) in a bid to find a means of improving traffic flow on some of Britain's busiest routes.
And at other sites the speed limit could be raised to 80mph to bring the country in line with Europe, the Daily Mail reports.
Motorways likely to see a reduction in speed limit include parts of the M25 possibly the northern section and its junction near Heathrow. The M6 through Birmingham, the M42 near Birmingham, parts of the M4, The M62 between Liverpool and Leeds and parts of the M8 between Glasgow and Edinburgh.
A DTLR spokesman said: "Traffic management is a major concern and reducing gridlock is a concern."
He added that options for achieving less congestion were being looked at by the Government.
Edmund King, executive director of the RAC Foundation, told the newspaper he would not support the 50mph plan. He said: "We would not back permanent reduction on the motorway network because it is not required for such strong limits to be in place at all times of the day.
"It would be a very draconian measure."

[img]images/smilies/mad.gif[/img][img]images/smilies/mad.gif[/img]
Interesting, I dont get how they think this will reduce congestion, from my experience areas of motorway with 50mph limits always seem to be MORE congested than normal, and look how traffic contracts when everyone slows to 70 to go past a cop car!!! Logically it doesn't add up to me, increasing peoples journey times equals more people on the road at any given point, surely??? Or is that the point, p!ss us all off until we give up using our cars!!!!

Disco

Bliidy spooling!

[Edited by Disco - 11/19/2001 10:50:39 AM]

Scoobychick

iTrader: (1)

You're having a laugh??? [img]images/smilies/mad.gif[/img] [img]images/smilies/mad.gif[/img] [img]images/smilies/mad.gif[/img]

Noooooooooooooooooooooooo - they can't do that! They should IMHO raise the limit to at least 80mph and make a minimum of 60mph on motorways (except where circumstances prohibit etc...)

WTF are they thinking?

I'm going to have a lie down in a darkened room.....

Sal [img]images/smilies/mad.gif[/img]



[Edited by scoobychick - 11/19/2001 10:54:42 AM]

chiark

Sal, unfortunately it's been pretty comprehensively proven that traffic flows better at slower speeds when gridlocked as it smooths the burstiness of the flow. This is why the variable speed limits on the M25 are still in place - it does actually work.

The M62 is a nightmare sometimes, and it would probably help.

But I feel that a variable speed limit is the way forward...

MorayMackenzie

Well, if it reduces the number of idiots having accidents on the M4 it should help overall flow and stop my 85mile journey taking over 2 hours each time I manage to get away early.

This morning it was a maroon Fiat Coupe Turbo on the central reservation eastbound and a white transit further down on hard shoulder... looks like the fiat driver attempted to cut in front of the transit, didn't manage to leave the typical 24" safety gap.

On Friday, get away early... great... 2.5 hours later get home having been stuck in stop start traffic for 2 hours because a van and a lorry decided to have an accident.

The thing that really annoys me is that the majority of serious accidents that have held up or simply stopped the M4 or M5 over the last 18months are reported to have been caused by lorry drivers or a combination of van and lorry drivers, but any action taken, such as periods of zero tolerance etc is taken unilaterally, rather than trying to address the specific problem itself... I've lost count of the number of times I see lorries wandering accross lanes because the driver is clearly not alert enough to be in control of the vehicle, probably due to exhaustion.

Adam M

In my experience, when 50 mph limits are in place, the traffic would be even worse had people continued at 70. It is difficult to see that things would have been worse without the restrictions.

Its like limiting the motorway to one lane through road works.

If you do it ten miles in advance, then everyone changes lanes over a longer period and there is no bottlenecking at the end. but people are impatient and b@stard jump in right at the end meaning all the patience was wasted and you are ground to a halt.

The same thing happens when filling up the back of a traffic jam.

To be honest it takes an indepth knowledge of fluid dynamics to understand traffic flow, so I dont believe it is for us to sit and judge. I personally was glad to hear the suggestion of the raise to 80 mph to bring us in line with europe.

Scoobychick

iTrader: (1)

Nick - show me the proof!!!!! pleeeeeeeeze...

I'm only going by what I see on the M25 Heathrow stretch. What they really need to do is educate some drivers as to the lane system and what it's there for. I'm sure half the problem is idiots sitting in the middle lane at a constant 60mph whilst oblivious to everything else around them. [img]images/smilies/mad.gif[/img] [img]images/smilies/mad.gif[/img] [img]images/smilies/mad.gif[/img]

Sal

Disco

I have to admit, enforcing lane discipline would make a huge difference.
Too many people seem embarassed to use the inside lane, feel the need to pull out 1/2 a mile before the target of their overtaking manuover etc,etc.

STi wanna Subaru

iTrader: (1)

There's simply too many lorries on our roads/motorways. Almost every accident I hear reported on the traffic news involves a lorry. Sort the railways out, get the heavy stuff off the roads and leave them free for cars.

M62/M621 junction coming out of Leeds towards Manchester is a nightmare. Although heavy traffic is to blame it is made so much worse by the convoy of lorries in the inside lane making it almost impossible to get onto the M62. It's like a moving roadblock.

chiark

Sal, you need proof? Where's your faith?

The turd sitting at 60mph in the middle lane won't be affected by this: it's intended to ease conjested areas.

I'd like to see a variable limit (50-80MPH) where necessary, such as at the Chesterfield junction on the M1, and on the M62 at rush-hour, which is as much fun as experimental bowel surgery (so I hear).

Nick.

M Hutton

I constantly drive in the variable speed limit zone on the M25, you sit there looking at the sign saying 'Queue warning' and then variable limit marker of 40 and think I wish I could go that fast.

Then as previously mentioned you get the prat that think the outside lane is fast so jusmps across causing everyone to brake and then because there is suddenly a space in the middle lane it seems to be moving faster they go back there with the same effect.

After fifteen miles of just staying in the same lane (inside) I actually caught up and undertook (not my fault the lanes were moving at different speed and as the sign was saying 'Avoid changing lanes' with the guy that was switching lanes all the time.

With the people that decide to sit in the middle and outer lanes, apart from shooting them on the hard shoulder, they should be pulled and educated by the police. After all you could argue for 'Driving without undue care and attention' the rules are to drive in the inside lane unless overtaking.

Nice BMW (isn't always) on the M4 today, I was going along on the inside lane at <cough> 70 when he was sitting in the outside. I decided after catching him up that I wouldn't undertake so I moved over and blipped the lights at him after sitting there for five miles and watching countless cars go through on the inside and middle lanes. Eventually he moved over, I drove past and then went back to the inside lane (he stayed in the middle lane) a bit later on he overtook me and gestured in a manner that showed I wasn't going to be on his Christmas card list.

Will the above is all to common, it does go to show there is a lack of understanding to how the rules of the road work, or that some people don't think they apply to them.

Education is more likely to ease congestion than variable speed limits.

(I shudder to think what would happen if I was ever allowed to drive a Police car - BMWs with jackets on hangers beware!)

mook

I personally reckon the variable limit works, so long as people stick by it and don't just think, 'well, it's still clear so I'll carry on at '70' until I hit the queue!' Increase to 80 also makes sense when it's clear

Regarding lane discipline on motorways, it is on another of my pet hates. Traffic flow slows to 70, everyone thinks, 'I can go quicker than 70 so move to the outside and wait for everyone to get out of the way' - so everyone sits in the outside and everything else is clear. My standpoint which I owuld argue to the police if pulled and questioned. You are allowed to undertake in queues, if lanes are travelling at different speeds due to queues, or (on dual carraigeways) the right hand lane is slowing to turn right. So, if everyone is sitting in the middle/outside lane they are creating a mobile queue and I see no reason why I shouldn't use the inside lane which tends to be clear for at least a mile ahead. Obviously I take care when doing this as I fully realise the blind spot on the passenger side is a lot bigger than the driver's side. It just p**ses me off tat w**kers sit in the outside locking everythin up [img]images/smilies/mad.gif[/img]

Richard Askew

...what are speed limits anyway??

Seriously - in places like the south side of Brum on the M42 and the northern end on the M6, the daytime traffic barely reaches this pace...if these restrictions were imposed they would have to have temporal variations... no point having a 50 limit at 4am is there?
Question: does a reduced speed limit reduce driver concentration and awareness??
Discuss........

RickyD

During the week maybe they could reduce the speed limit to 50mph on Motorways & Dual Carriage ways!

I travel down the A1 (South) and most of the time through the week 50mph is generally the maximum speed you can do anyway, having only two lanes, that's both to & from my work place. Once I'm off the A1 I can use the Impreza's true performance figures, meaning 'mid-range performance'

If they made it 50mph all the time & would go straight out & buy the slowest diesel car available!!!

Cheers

RickyD

nom

The bit where the 50 limit in conjested traffic doesn't work is when it's broken - so most of the time, then. The 'speed kills' that we're all hammered with is, technically, bollocks. Everyone travelling at the same speed is no problem - it's when stationary objects are thrown in (pedestrians, brick walls, etc.) that there are problems. A rapid change of speed can kill, therefore the greater the speed difference between vehicles, the more likely there is to be an accident (especially the vehicles with more momentum - lorries, vans, etc.) So the obvious solution is to make sure that all vehicles travel at the same sort of speed. Setting a 50 limit means that vehicles will have a greater varience in speed than usual (the relative speed difference between the people who obey the limit & those who it apparently does not apply to increases the lower the set speed limit - so a lower speed limit is more dangerous if people ignore it; the lower it is, the more it seems to be ignored from my experience...).
Also, fluid mechanics dictates that the lower the speed of flow, the larger the conduit needs to be to carry the same flow rate. i.e., to drop the speed limit, more lanes must be provided to carry the same number of vehicles. If the number of lanes remains the same but the flow rate is artificially reduced (i.e. a speed limit), the result is a pressure increase upstream of the restriction - translates to compression of traffic - cars getting closer to each other. A point is then reached when a shockwave is returned from the reduction - again roughly translated as hard braking - which then, if the drivers do not compensate heavily & far in advance of the shockwave, traffic can compact to such a point that there is an accident.
Thoroughly engineeringy way of looking at things. Dull but true.
I personally think it would be nice if some of the people who design traffic systems knew something about fluid dynamics, or at least drove or maybe walked/cycled about in the real world from time to time.

Beemer_Deano

IMHO, increase the speed limits and reduce the number of lorries on the road by running more overnight.

Or (agreeing with STI) get more freight on the railways. Trucks might as well be trains anyway - they seem to have to travel 2" apart (especially past slip roads), then flash you when you "cut in".

dharbige

nom - not quite the whole truth.

The idea of a variable speed limit is, as chiark mentioned, to make a smoother, more constant flow of traffic. To continue with the fluid dynamics analogy, this gives reduced turbulence in the flow, and therefore less energy expended in motion other than in the intended direction of travel.

Your comment about a larger conduit being required for a slower flow and the same flow rate is, generally, correct. However, its application to this analogy is based on an incorrect premise - that the speed LIMIT is the speed of the flow.

The whole point of the variable speed limit exercise is to increase flow RATE (i.e. the number of vehicles passing through a section of road over a period of time), and this is not directly related to the maximum speed a vehicle is allowed to travel at any particular point.

As an interesting () exercise, try calculating how long it takes to travel 2 miles, firstly at a fixed speed of 50mph, and secondly at a mixture of 20mph faster and 20mph slower (say half the distance at 70mph, half the distance at 30mph).

David H.

GazP

I use the M62 to get into Liverpool some days, and the average speed of the traffic is about 80 - 85 MPH. The police seem fine with people going at that speed as well. Why don't the government realy user their power and raise all the speed limits for cars to bring us into the 21st century? OK, bad weather and other factors might be cause for a temporary lower limit, but other than that I see no reason not to raise the limit. As for the 50 MPH limit, you can GUARANTEE that this limit will be policed VERY strictly, and anyone found to be going faster will get the usual penalty points and a fine. Call me cynical but it sounds to me like revenue gathering again. Why else are people going to have to pay to enter cities? It's all anti motorist with this government, why don't they just go and hassle someone else like the rich?

nom

David -
Agree with your stuff there - the turbulence is the bit that needs to be removed, and that is the idea of the lower speed limit. But the problem that I have with this system is that the speed limit is usually ignored by at least a few people, and therefore there is more turbulence, especially if those who 'absolutely must get there NOW' change lanes all the time.
I was trying to simplify things a bit .
Overall, the variable speed limit should work very well, as long as everyone pays attention to it. It's probable that if everyone did, the limit could actually be raised as the traffic should clear.
The same thing I think works in towns - The now thoroughly exciting A40 coming into London jumps eratically between 30 & 40 about every 500m if the signs are followed precisely - naturally there's a smattering of Gatsos around to catch everyone - even those of us trying to stick to the limit that we have no idea what it is at that particular second... Anyway, it seems to be getting lower & lower, & I think it's because of the 'doesn't apply to me' driving: at 50, people do 70; at 40, 50; and at 30, 50 as well, apparently. Scares the poo out of me now that bit of road with the 'Oxford Tubes' driving in the 30 limit at 60. Anyway, the limit is reduced to the point that most people's breaking-of-the-limit is within the limit that they are happy about, i.e. if 30 is specified, people drive at 50 with ocassional hard-braking to 30 at the Gatsos. How this is considered safer I have no idea...
Begninning to drift off the point now. I'll stop raving .