Arguments for raising the UK motorway speed limit

[LoonR1]

Lil'RedGTO said:

Fair point, although I suspect that those who admitted to breaking the motorway speed limit have done so more than once and in fact do so with some regularity. I am not sure exactly how the question in the RAC survey was worded, but I get the impression it was along the lines of "Do you speed on the motorway?" Of course, the point about bringing the law into disrepute is just one argument. I am interested in all arguments, for and against.

I pretty well ignore it and don't really care too much what the limit is. I drive at a speed I want to when it's freeflowing enough normally up to 90mph (note I'm not one of those wibblist a panicking about being arrested amd writing leptons instead). I'm not too worried about being nicked as I seem to be lucky / observant enough to get away with it a lot. I don't think people would drive at 80 even if it were increased, they seem happy at 55 nowadatys.

[Phatboy317]

Jon1967x said:

One reason is certain vehicles are limited to 55. The spread of speed is a danger.

But you don't want to spend too much time next to a 55mph lorry, because you're toast if they suddenly change lanes while you're next to them, so it's good for your safety to get past as quickly as possible.
OTOH, if they suddenly change lanes while you're still behind then you want to be going slow enough to be able to avoid running into the back of them.
The speed which mathematically gives you the best compromise is just over 90mph.

Also, a good (but not excessive) speed differential is really essential for the smooth flow of traffic. If you're taking ages to pass another vehicle then you're probably going too slow - regardless of what speed you're doing, as you're limiting the dynamic room to manoeuvre for all the traffic around you, particularly those behind you.

[Jon1967x]

Phatboy317 said:

Jon1967x said:

One reason is certain vehicles are limited to 55. The spread of speed is a danger.

But you don't want to spend too much time next to a 55mph lorry, because you're toast if they suddenly change lanes while you're next to them, so it's good for your safety to get past as quickly as possible.
OTOH, if they suddenly change lanes while you're still behind then you want to be going slow enough to be able to avoid running into the back of them.
The speed which mathematically gives you the best compromise is just over 90mph.

Also, a good (but not excessive) speed differential is really essential for the smooth flow of traffic. If you're taking ages to pass another vehicle then you're probably going too slow - regardless of what speed you're doing, as you're limiting the dynamic room to manoeuvre for all the traffic around you, particularly those behind you.

You have invented and continually preach a new branch of mathematics that noone else in the world understands. I'd love to see your workings on why 90 and 55 are the best mix of speed on the motorway

You also seem to suggest managed motorways should be speeding up traffic not slowing it down to increase throughput?

[LoonR1]

Jon1967x said:

Phatboy317 said:

Jon1967x said:

One reason is certain vehicles are limited to 55. The spread of speed is a danger.

But you don't want to spend too much time next to a 55mph lorry, because you're toast if they suddenly change lanes while you're next to them, so it's good for your safety to get past as quickly as possible.
OTOH, if they suddenly change lanes while you're still behind then you want to be going slow enough to be able to avoid running into the back of them.
The speed which mathematically gives you the best compromise is just over 90mph.

Also, a good (but not excessive) speed differential is really essential for the smooth flow of traffic. If you're taking ages to pass another vehicle then you're probably going too slow - regardless of what speed you're doing, as you're limiting the dynamic room to manoeuvre for all the traffic around you, particularly those behind you.

You have invented and continually preach a new branch of mathematics that noone else in the world understands. I'd love to see your workings on why 90 and 55 are the best mix of speed on the motorway

You also seem to suggest managed motorways should be speeding up traffic not slowing it down to increase throughput?

100% this. How on earth a set figure of 90 can be decided on is ridiculous. Would a 15 year old 1.1 Fiesta be OK to do that? Unbelievable.

[Dammit]

It's because you can't divide 90 by 55 and get an integer, therefore the lorry and the car can never be side by side, which is of course when the danger happens.

[Phatboy317]

Jon1967x said:

Phatboy317 said:

Jon1967x said:

One reason is certain vehicles are limited to 55. The spread of speed is a danger.

But you don't want to spend too much time next to a 55mph lorry, because you're toast if they suddenly change lanes while you're next to them, so it's good for your safety to get past as quickly as possible.
OTOH, if they suddenly change lanes while you're still behind then you want to be going slow enough to be able to avoid running into the back of them.
The speed which mathematically gives you the best compromise is just over 90mph.

Also, a good (but not excessive) speed differential is really essential for the smooth flow of traffic. If you're taking ages to pass another vehicle then you're probably going too slow - regardless of what speed you're doing, as you're limiting the dynamic room to manoeuvre for all the traffic around you, particularly those behind you.

You have invented and continually preach a new branch of mathematics that noone else in the world understands. I'd love to see your workings on why 90 and 55 are the best mix of speed on the motorway

You also seem to suggest managed motorways should be speeding up traffic not slowing it down to increase throughput?

The compromise is best when the time taken to pass the lorry is the same as the time it would take to slow down to the speed of the lorry, starting from the point behind the lorry where it's still just possible to slow down behind it. The maths is simple.

I'm talking about free-flow conditions - not necessarily where capacity is approaching maximum.
Have you never observed a 'plug' of bunched-up traffic on an otherwise free-flowing motorway?

Edited by Phatboy317 on Wednesday 18th February 23:42

[Kawasicki]

LoonR1 said:

Would a 15 year old 1.1 Fiesta be OK to do that?

90mph is no problem for the smallest engined 2005 Fiesta.

[Jon1967x]

H

Phatboy317 said:

Jon1967x said:

Phatboy317 said:

Jon1967x said:

One reason is certain vehicles are limited to 55. The spread of speed is a danger.

But you don't want to spend too much time next to a 55mph lorry, because you're toast if they suddenly change lanes while you're next to them, so it's good for your safety to get past as quickly as possible.
OTOH, if they suddenly change lanes while you're still behind then you want to be going slow enough to be able to avoid running into the back of them.
The speed which mathematically gives you the best compromise is just over 90mph.

Also, a good (but not excessive) speed differential is really essential for the smooth flow of traffic. If you're taking ages to pass another vehicle then you're probably going too slow - regardless of what speed you're doing, as you're limiting the dynamic room to manoeuvre for all the traffic around you, particularly those behind you.

You have invented and continually preach a new branch of mathematics that noone else in the world understands. I'd love to see your workings on why 90 and 55 are the best mix of speed on the motorway

You also seem to suggest managed motorways should be speeding up traffic not slowing it down to increase throughput?

The compromise is best when the time taken to pass the lorry is the same as the time it would take to slow down to the speed of the lorry, starting from the point behind the lorry where it's still just possible to slow down behind it. The maths is simple.

I'm talking about free-flow conditions - not necessarily where capacity is approaching maximum.
Have you never observed a 'plug' of bunched-up traffic on an otherwise free-flowing motorway?

Edited by Phatboy317 on Wednesday 18th February 23:42

Your premise requires perfect behaviour of all involved. Unfortunately even a fluid doesn't work like that.

The plug that you mention is because a lorry travels at 50, it's uphill so another lorry starts to overtake doing 55, a van overtakes doing 60, an old chap is doing 70, someone who's prepare to go faster does 80.. 5 lanes gone befire you've reached your 90. Even in light traffic these situations will statistically arise

Edited by Jon1967x on Thursday 19th February 08:14

[LoonR1]

Kawasicki said:

90mph is no problem for the smallest engined 2005 Fiesta.

is it 2020 already? In any case the point wasn't whetehr it'll get to 90, it's whether this magical new figure applies consistently to all cars. Phatboy decided that 90mph was the standard for all cars and absolutely fine. Just as 70 isn't a suitable line for all cars as many can go quicker and more importantly stop quicker, then why is 90 OK?

If he's going to do this sort of maths we need his workings and ideally use a sliding scale for each car.

[ORD]

What in the name of Blod are half of you talking about?!

There is no sensible argument against increasing the speed limits to at least 80mph. It is simply an example of vocal pressure groups fking up policy for everyone else.

[Lil'RedGTO]

Well, playing devil’s advocate, the two obvious ones are (a) the possibility of a slight increase in deaths and serious injuries as a result of the slightly higher speeds, and (b) increased emissions as engines work harder at higher speeds.

I’m not sure what the answer to (a) is, and it’s a tricky one as no politician wants to be seen to be responsible for a measure that leads to more death and injury and harping screams from Brake of “We told you so”. In theory higher speeds could lead to an increase in both the frequency and severity of accidents. It may be possible to point to other European nations with 80mph limits and observe that their death tolls are not that greater than ours, but if they are even slightly greater that is not particularly persuasive. I suppose one answer is to trial increased limits on a few motorways for a year or so and then compare accident rates, then we would know for sure. Another more controversial answer is that the economic benefits would outweigh the cost of the accidents, but again that is a hard sell for a politician.

As for (b), I suppose one answer is that cars are more efficient than ever and the current regime does not (and should not) prevent individuals from using more fuel if they choose as long as they are happy to pay the tax at the pump.

[tapereel]

Lil'RedGTO said:

Well, playing devil’s advocate, the two obvious ones are (a) the possibility of a slight increase in deaths and serious injuries as a result of the slightly higher speeds, and (b) increased emissions as engines work harder at higher speeds.

I’m not sure what the answer to (a) is, and it’s a tricky one as no politician wants to be seen to be responsible for a measure that leads to more death and injury and harping screams from Brake of “We told you so”. In theory higher speeds could lead to an increase in both the frequency and severity of accidents. It may be possible to point to other European nations with 80mph limits and observe that their death tolls are not that greater than ours, but if they are even slightly greater that is not particularly persuasive. I suppose one answer is to trial increased limits on a few motorways for a year or so and then compare accident rates, then we would know for sure. Another more controversial answer is that the economic benefits would outweigh the cost of the accidents, but again that is a hard sell for a politician.

Well unfortunately it is a fact that serious and fatal injuries increase as speed increases. The only way you can avoid this is perhaps get drivers to promise they won't crash. Maybe as well as promising get them to join a driving gods website and all will be OK. That will be just as effective as your other suggestions.
Comparisons with other countries is a non-starter.
Getting a politician to sponsor a move that will increase death and serious injury is a tough one. Perhaps you need to speak with the haulage industry representatives who have made a sucessful bid to increase HGV speed limits from 40 to 50 on single carriageways; not as difficult because everyone knows they were already defying this at 56mph in any case.

Lil'RedGTO said:

As for (b), I suppose one answer is that cars are more efficient than ever and the current regime does not (and should not) prevent individuals from using more fuel if they choose as long as they are happy to pay the tax at the pump.

Well NO is about to take over from CO2 as the devil's gas for the government so no-go with that one I reckon.

[Dr Jekyll]

tapereel said:

Well unfortunately it is a fact that serious and fatal injuries increase as speed increases. The only way you can avoid this is perhaps get drivers to promise they won't crash. Maybe as well as promising get them to join a driving gods website and all will be OK. That will be just as effective as your other suggestions.
Comparisons with other countries is a non-starter.
Getting a politician to sponsor a move that will increase death and serious injury is a tough one. Perhaps you need to speak with the haulage industry representatives who have made a sucessful bid to increase HGV speed limits from 40 to 50 on single carriageways; not as difficult because everyone knows they were already defying this at 56mph in any case.

You are assuming the very point you are trying to prove.

Increased average speeds do not necessarily lead to increased serious and fatal injuries, increased speed limits do not necessarily lead to increased average speeds anyway. In the case of largely unobserved limits they rarely do, they can actually lead to a fall. When the dual and single carriageway NSLs were raised in the 1970s from 60/50 to 70/60, there was a tiny increase in speeds and an equally tiny reduction in accidents.

[Jon1967x]

Dr Jekyll said:

You are assuming the very point you are trying to prove.

Increased average speeds do not necessarily lead to increased serious and fatal injuries, increased speed limits do not necessarily lead to increased average speeds anyway. In the case of largely unobserved limits they rarely do, they can actually lead to a fall. When the dual and single carriageway NSLs were raised in the 1970s from 60/50 to 70/60, there was a tiny increase in speeds and an equally tiny reduction in accidents.

You are hanging on to a bit of a wishful thinking.

We've had this argument a zillion times on here. Increasing speed limits will raise the average speed (or put it another way, it certainly won't decrease it), all other things being equal. Accidents will continue to happen and irrespective of whether the speed is a factor, lets assume not, the higher speed will result in higher fatality. Its where the laws of physics meets the biology.

We need to be careful though for what we wish for, the politically acceptable answer will probably be either 70, or maybe 80 mph but with long distance enforcement. I would MUCH prefer the current system than knowing that a computer is clocking my location and works out the average speed I must have driven to go between any 2 points. I, like many, drive from the top to the bottom of the M40 for instance, imagine a system that measures the average speed over that whole stretch and issues NIP if the average was 79 mph... that really would give us something to complain about. We know the technology is there, its used in road works. We know they clock cars at locations, we have ANPR.

Higher speed limits will only come with greater and greater enforcement, hence the earlier questions, which would you prefer, todays 70 with the odd ticket or an 80 where it means 80?

[Phatboy317]

Jon1967x said:

H

Phatboy317 said:

Jon1967x said:

Phatboy317 said:

Jon1967x said:

One reason is certain vehicles are limited to 55. The spread of speed is a danger.

But you don't want to spend too much time next to a 55mph lorry, because you're toast if they suddenly change lanes while you're next to them, so it's good for your safety to get past as quickly as possible.
OTOH, if they suddenly change lanes while you're still behind then you want to be going slow enough to be able to avoid running into the back of them.
The speed which mathematically gives you the best compromise is just over 90mph.

Also, a good (but not excessive) speed differential is really essential for the smooth flow of traffic. If you're taking ages to pass another vehicle then you're probably going too slow - regardless of what speed you're doing, as you're limiting the dynamic room to manoeuvre for all the traffic around you, particularly those behind you.

You have invented and continually preach a new branch of mathematics that noone else in the world understands. I'd love to see your workings on why 90 and 55 are the best mix of speed on the motorway

You also seem to suggest managed motorways should be speeding up traffic not slowing it down to increase throughput?

The compromise is best when the time taken to pass the lorry is the same as the time it would take to slow down to the speed of the lorry, starting from the point behind the lorry where it's still just possible to slow down behind it. The maths is simple.

I'm talking about free-flow conditions - not necessarily where capacity is approaching maximum.
Have you never observed a 'plug' of bunched-up traffic on an otherwise free-flowing motorway?

Edited by Phatboy317 on Wednesday 18th February 23:42

Your premise requires perfect behaviour of all involved. Unfortunately even a fluid doesn't work like that.

The plug that you mention is because a lorry travels at 50, it's uphill so another lorry starts to overtake doing 55, a van overtakes doing 60, an old chap is doing 70, someone who's prepare to go faster does 80.. 5 lanes gone befire you've reached your 90. Even in light traffic these situations will statistically arise

Edited by Jon1967x on Thursday 19th February 08:14

What premise?

Small speed differentials do tend to clog up the works.
Just one example: you want or need to change lanes, due to slower traffic ahead or vehicles joining the motorway.
A small speed differential will hugely increase the probability that you're going to be unable to change lanes in the time you have available, because there's someone sitting next to you, so then your only option is to slow down or brake.

[Lil'RedGTO]

I personally think comparisons with other European countries are valid, given broadly similar cars and roads, and many of them seem happy with the compromise of 80mph. I don’t really buy this idea that continental motorways are SO much better or quieter than ours. Were those countries always 130kph/80mph or did they increase their limits at some point?

I agree that pollution and NOx is an obstacle, given recent consultations on REDUCING the speed limit to 60mph on a couple of motorways where local air pollution is a problem. Is it perhaps one that may be surmountable as older (early/mid-2000s) diesel passenger cars age off the market and/or are “fiscally disincentivised” off the roads?

The point about the haulage industry securing an increase to 50mph is an interesting one and offers a glimmer of hope. The argument that “everyone knew they were already defying the 40mph limit” is much the same point being made about the 70mph limit and it is about legalising existing widely prevalent behaviour.

I agree that there is a risk of bringing greater enforcement upon ourselves with an increased limit, but it may be going that way anyway. Indeed, if there is ever a genuine attempt to strictly enforce the motorway limit, that might itself prompt a public outcry and a review of the limit. I can see the argument for not prodding the hornet’s nest, however.

[Dr Jekyll]

Jon1967x said:

which would you prefer, todays 70 with the odd ticket or an 80 where it means 80?

Obviously 80. Then I can drive at up to 80 when conditions permit, which I can't do with a 70 limit.

[Munter]

Dr Jekyll said:

Jon1967x said:

which would you prefer, todays 70 with the odd ticket or an 80 where it means 80?

Obviously 80. Then I can drive at up to 80 when conditions permit, which I can't do with a 70 limit.

If we're only going to increase it by 10 mph. What's the point.

I regularly drive from the Midlands to Taunton. The stretch of motorway is about 123 miles. The whole journey takes about 2:30 including all the in town bits and fafing about. And I set the cruise at 70 on the GPS on the motorway. It gives me about 52 mpg.

Now if we increase the limit to 80 and I drive at it. And we assume I could maintain that for the full 123 mile section on the motorway. (Although in reality I can't maintain 70 due to other traffic). I'd save 13 minutes. But fuel consumption would go from 52 to about 47 (based on a short period of...err...testing...by the wife).

Over the return journey of 5 hours, I'd save 26 minutes and it'd cost me an extra £2.60 ish. These are hardly big changes. Is it really worth the fight?

Up it to 120mph and then we can really start talking. The motorway could then be enjoyable driving and I'd save almost an hour and a half on those days.

[tapereel]

Lil'RedGTO said:

I personally think comparisons with other European countries are valid, given broadly similar cars and roads, and many of them seem happy with the compromise of 80mph. I don’t really buy this idea that continental motorways are SO much better or quieter than ours. Were those countries always 130kph/80mph or did they increase their limits at some point?

I agree that pollution and NOx is an obstacle, given recent consultations on REDUCING the speed limit to 60mph on a couple of motorways where local air pollution is a problem. Is it perhaps one that may be surmountable as older (early/mid-2000s) diesel passenger cars age off the market and/or are “fiscally disincentivised” off the roads?

The point about the haulage industry securing an increase to 50mph is an interesting one and offers a glimmer of hope. The argument that “everyone knew they were already defying the 40mph limit” is much the same point being made about the 70mph limit and it is about legalising existing widely prevalent behaviour.

I agree that there is a risk of bringing greater enforcement upon ourselves with an increased limit, but it may be going that way anyway. Indeed, if there is ever a genuine attempt to strictly enforce the motorway limit, that might itself prompt a public outcry and a review of the limit. I can see the argument for not prodding the hornet’s nest, however.

The haulage industry based their campaign on the economic benefit of a shortened journey time NOT that their members were already driving foot-to-the-floor at 56mph.

[Lil'RedGTO]

I imagine that the economic argument, which applies equally to private individuals, who are all economic agents, is probably the most important from the Government's perspective, if the safety concerns could be assuaged. Increasing the motorway speed limit would presumably bring economic benefits by reducing journey times, especially at off-peak times, meaning people spending less time travelling and more time being economically productive (whether working or spending money on leisure activities). Time saved might be small, but multiply it by millions and the sums are huge (see my earlier post on the projected figures for the Netherlands). Furthermore, these benefits could be reaped at little or no cost to the taxpayer, the Government having already spend billions on the motorway network and private individuals having already invested huge sums of money in buying private vehicles that are already capable of travelling safely at 80mph.