There has to be a limit and that is the limit they set. I don't think anyone suggests it is magical.

Has anyone here ever experienced a tire blow at 70mph?

Honda FRV (dont laugh!), coming over from Holmfirth towards Manchester over the tops. On a wide sweeping righthander at circa 80and the nearside front blew. Slid further out and the lefthandside of the car was kicked up by a low-kerb. opposite-locked it to bring it back down and Bobs your Uncle 🙂

The thought of doing 70mph in a Moggy is scary in its self 😉

"Can somebody please explain to me what is so magical about 70mph?"

Nothing, but advocates of a change ought to be a very strong reason for increasing it. A few minutes saved on journeys at the expense of extra emissions, more severe accidents, and reduced road carrying capacity would not seem to be much of a reason…

Motorway speed limits will only ever be reduced – not increased.
Aracer – Not only will every single slip road and junction need altered, every single sign, gantry and safety barrier will need replaced.
The lengths of a slip road is designed to allow safe braking from the time you leave the motorway to the junction at the end (although there are a few instances where this is not the case).
Signs are designed so that you can read them from a given distance while travelling at 70mph, all to do with speed / time / distance travelled / reaction.
Although safety barriers are tested at speeds greater than 70mph, they can't be guaranteed to work if hit at greater speeds. The cost of replacing all of these throughout the country would be in the £billions.

To be honest, although I like going quickly, I think 70mph is ample enough. In fact my wife often complains I drive too slowly on motorways.

Quite the reverse on A roads though 'cause I like chucking my car into corners and stuff – it's where the fun is at. 🙂

Although safety barriers are tested at speeds greater than 70mph, they can't be guaranteed to work if hit at greater speeds.

I'd be amazed. The amount Ive seen peeled open/cracked open on the M60/M62 worries me. worse still are those tensile-wire central reservations as well. What are they going to stop?!

I thought the idea was that they are designed to bend and be broken off the vertical posts when hit so that they redirect the energy of the crash and prevent the vehicle reaching the opposite carriageway?

Those wire ones are to absorb energy and stop the vehicle being bounced back on to it's own carriageway.

Motorway speed limits will only ever be reduced – not increased.

When Ireland went metric in 2005 the motorway limit went up from 70mph to 120kph (~75mph).

They also took the opportunity to reclassify many single carriageway roads as either 100kph or 80kph (so some reduced from 60mph to ~50mph).

Not only will every single slip road and junction need altered, every single sign, gantry and safety barrier will need replaced.
The lengths of a slip road is designed to allow safe braking from the time you leave the motorway to the junction at the end (although there are a few instances where this is not the case).

In that case, given that nearly everyone drives at 80mph already, I wonder how anyone manages.

i thought speed limits weren't designed to decrease the number of accidents, just decrease the severity of them when they occur. After all, people will always make mistakes.

Anyway, i'd expect emissions will play a bigger part in whether the speed limit should be changed than safety. The faster you can get places in a car, the more people use them too, and there seems to be a drive to reduce car usage at the moment.

and there seems to be a drive to reduce car usage at the moment.

Except they have a car scrappage scheme to encourage people to buy new cars, not stop using them. If the Government wanted us to stop using them, they would give us free public transport or bikes or something in exchange for giving up our cars.

Can't believe someone suggested that Spanish drivers are anything other than idiots. I live in Spain and some of the things ive witnessed are scary. The one thing i am certain about is that the Spanish have absolutely no concept whatsoever of other people around them, not just in driving but in every walk of life.

Except they have a car scrappage scheme to encourage people to buy new cars, not stop using them. If the Government wanted us to stop using them, they would give us free public transport or bikes or something in exchange for giving up our cars.

Ah you see. When the recession is over Labour will focus yet again on VED and other measures aimed at motorists.

Ah you see. When the recession is over Labour will focus yet again on VED and other measures aimed at motorists.

VED's only a very small part of the cost of running a car…

The Car Scrappage scheme has **** all to do with being green and everything to do with trying to prop up the economy through whatever means possible.

Motor industry is on its knees. Banks need to make safe loans to recover. Folks need finance when buying new cars.

The Car Scrappage scheme has **** all to do with being green and everything to do with trying to prop up the economy through whatever means possible.

Well precisely – the Government has long claimed to want to be green, whilst at the same time doing nothing to improve the public transport system (well, screwing it over even more really). And this scheme has proven that they do not want it. If they WANTED to be green, the current economic climate would have given them a perfect excuse to do something about it, yet they still push people into car buying.

And if us all buying cars is their solution to propping up the economy, then gawd help us all…

If they WANTED to be green, the current economic climate would have given them a perfect excuse

Sadly being green and strong economic growth are not really very compatible.
If they were then we wouldn't need green legislation and taxes etc.

"The lengths of a slip road is designed to allow safe braking from the time you leave the motorway to the junction at the end (although there are a few instances where this is not the case)."

Have you ever driven on an Autobahn? The slip roads are about half the length of British ones, and generally have a very steep bend at the end of them.

I also think that German drivers are pretty bad, no concept of braking distance whatsoever, they leave themselves no escape route if things in front got tits up, they don't know what an indicator is and they absolutely LOVE pulling out on eachother. I've only been living here for 8 months and i've seen some horrendous smashes on the roads. There was a 260 vehicle pile up on th A2 near Hannover a couple of weeks back, apparently caused by sun glare on the wet road, more likely everyone driving up eachothers arses too fast.

The lengths of a slip road is designed to allow safe braking from the time you leave the motorway to the junction at the end (although there are a few instances where this is not the case).

Presumbly there's carnage on the ones which don't comply (I can think of a few)? Or maybe all the people who do drive at 80 fail to stop at the end of slip roads? No?

As mentioned above, 80 (or more) is the defacto speed anyway – yet modest breaking the speed limit in good conditions really isn't a factor in motorway accidents, whatever the "speed kills" brainwashed on here seem to think.

Anyway, it's not at all as simple as is being made out. From a road safety perspective, does it make sense to discredit speed limits in general by imposing one that nobody respects on the safest roads in the country, thus making it less likely for people to stick to them on the roads where it actually matters?

Fair enough there isnt a case for excess speeding , 80mph is more than enough if you are going over the limit. Whats really scary is people who put no planning or observation into their driving. I regularly drive late evening or at night to avoid traffic and the amount of people you see leaving it late braking at the last minute behind some artic even when theres ample time and space for them to MSM and move on.
Remember nobody will willingly pile their motor into another or the barrier but if your not looking your going to cause chaos.

I think the limits too low personally, But there are a lot of people who drive on the motorway who havent a clue what they're doing so its safer not to increase it.

I tried to get from Harrogate to Leeds and back today in an hour, It didnt happen because of morons dithering, delaying and hogging lanes

The reason they won't increase the Speed limit is one of capacity, The faster you go the more space you need (2 seconds is further at 100 than at 70). So the faster you go the less vehicles can occupy the limited space on a motorway at anyone time (there are calculations done by the DfT that show this).
As for some of the issues raised. Hola, there should be no more wire rope central reserve barriers, all new barriers will be concrete when replaced at end of life. djglover, The M42/M25 managed motorway schemes will be implemented in areas of high congestion such as M60, M56/M6/M62 interchanges and Birmingham box. (Now I sound like a Highways Agency mouthpiece which I am not)

The limits aren't too low. Too many times Ive seen rain and commuters merging on the M62 towards the Saddleworth turnoff.

You might be able to afford a 40k car with steering control, stability, accident assist etc etc but theres still something thats needed, common sense.

The limit could easily be raised without the vast modifications people are claiming, but a) it's not a very green thing to do, power required increases with the square of the speed, b) 80 makes sod all difference to even long journey times in the overall scheme of things and c) sure some things may then fall outside spec, but actually most items on the motorways are rolling improvements as and when they need to be upgraded. Lots of the existing barriers etc were not up to spec a decade ago and are an ongoing improvement. It's still highly unlikely. As Steven says, the one thing we suffer from is overcrowding of the roads, the way to get more cars through per unit time is to slow them down and get them closer together – simple as that.

The wire rope barriers are actually pretty damn good at their job, which is to deflect the car back into the carriageway they left at a shallow angle rather than not move at all. This video demonstrates it clearly:
http://www.youtube.com/watch?v=10L8421s18Q
The last thing you want is a barrier that's such a hard impact it kills the occupant, but also you dont want them passing through to the next carriageway – the ideal is the barrier reducing the energy of the impact and pushing them back across.

Steven – whats this about concrete barriers, loads of new barriers going in where I drive, most of them being plain old armco still?

M25 has alot of concrete?

Raise the limit and drivers will raise their perceived limits higher. Lower the limit to 60 and drivers will think speeding is 70.

No idea about the M25 – its 12 months since I skirted round a few junctions of it, it didn't look any different to any other motorway though to me. Concrete barriers make sense except for from an ecological point of view, though they probably do help contain the road noise from neighbours fairly well – reflecting it up and out rather than sideways.

Regardless of barrier type, freak accidents can still occur…

Fatigue "worse than speed"

“We all do roughly the same speeds on a motorway so it is rarely a cause of crashes,” he said. “Speed can be more of a factor off the motorway, but on it it’s not really an issue.”

As I've always said, glad to see the authorities agree on that at least.

The new HA spec for central reserve barriers is concrete incorporating the "dutch step" profile to deflect vehicles (some motaways sections completed are M6 near Stafford, M60 near Cheadle, M61 J3-4 is in progress).Crash damage is replaced like for like. The main reason for this is to reduce HGV crossover which nearly always results in a fatal accident. Verge barriers can still be corrugated safety fencing (armco) or box section barrier, sometimes concrete is used particularly around railway bridges.
Wire rope barriers were notorious for killing motorcyclists.

http://www.highways.gov.uk/knowledge/11569.aspx

Says it better than I could

Cheers Steven, good for a read.

Wire rope barriers were notorious for killing motorcyclists.

Slice and dice is term.

I have an horrendous 'wmv' video file showing what happens when a truck crashes through the central barrier. Unfortunately, I have no idea how to post it on here

(mr MC posting)

what grips my sh1t more than Mway speed limits is the de-facto change in the national non Mway speed limit to 50mph. Recently did an advanced police driver course where the policy is to only "make progress" in national limits. We drove all over the country and vast tracts of rural A-road have been converted to 50mph, with little or no justification. This change only exacerbates the diabolical "sunday driver" mentality, when someone does 45mph on a rural stretch, then continues at 45mph through a village.

Poor driving is a far greater factor than speeding per se, on many occasions the posted speed limit might be way to fast for local conditions.

In terms of re-designing motorways, my understanding was that they were designed way in excess of the parameters that the speed limit would set-the tightest Mway curves have a "critical speed" (ie maximum speed you can make the curve) comfortably in 3 figures. I dont believe that sign size, spacing, etc is so marginal that an increase in speed limit would require a total redesign/rebuild.

Coffeeking, I believe drag force goes with the square of velocity, so the power need to overcome it goes with the cube of velocity, which is a pedantic way of making your point even more strongly.

If the Government wanted us to stop using them, they would give us free public transport or bikes or something in exchange for giving up our cars.

CTW scheme? Although to be fair, that was introduced before the money meltdown….

Only had the one blowout – on the way back from a passed MOT. I came back into Aberdeen along the south Deeside Road – much loved by motorcyclists for its tight twisty bends and occasional long straight.

The front WHEEL collapsed as I went over a catseye – managed to get it back under control and stopped literally inches away from a 40 foot drop into the river below (though the trees might have broken my fall 😯 ).

Coffeeking, I believe drag force goes with the square of velocity, so the power need to overcome it goes with the cube of velocity, which is a pedantic way of making your point even more strongly.

But you've got to remember that if you're going faster you get there earlier, so energy required is only proportional to the square of speed. That would of course be assuming everything else was equal, which as usual it's not – when the majority of cars on the motorway get less MPG at 70 than I get at 80 I don't accept the argument that I'm an eco-terrorist.

The congestion argument is a pretty silly one – if it's that congested you can't do 70 anyway (and remember we're only talking about legalising doing 80, not changing the speed people actually drive at). Why shouldn't you be allowed to do 80 when it's quiet because sometimes it's congested? By the same argument, the limit should be 50 or 40 because sometimes it's not safe to do more than that, or that is the optimum speed for traffic flow.

Lets sum this up:
want to reduce accidents – penalise bad driving
want to reduce congestion – have variable speed limits (which work properly, like the M25 ones, not the M42 ones which appear to have some additional agenda to slow you down more than necessary)
want to help the environment – ban fuel guzzlers from motorways
want to make people respect the law more – raise the speed limit on motorways to the speed which many people already do quite safely
want to prevent people speeding where it really matters – set all speed limits sensibly so you don't foster disrespect for them, and if necessary have rigid enforcement, which people will mind a lot less if it's not seen as a revenue raiser rather than a safety issue

Just another quick question though. If there really isn't a significant difference in journey time between 70 and 80, then why not make people take a compulsory 10 minute rest every hour? That would make far, far more difference to road safety, yet make no more difference to people's journey times.

How are you going to make people have a compulsory 10 minute break every hour?! Maybe put a special device that cuts the engine after 50 minutes? Even if workable, people like yourself would just drive faster between 'breaks' to make up for the delay.

Everyone has a perceived "max" they dare go over the 70mph limit. To think for one minute raising it to 80 would mean people wouldn't then apply their logic to the faster limit is naive at best.

Basically this whole argument for an increase. revolves around people thinking they should go faster because they are good drivers, have good car, are perfectly capable, and assume everyone is like them.

Face facts – we don't have a decent police force (in terms of manpower) to crack down on tailgaters, bad drivers, middle lane hoggers.

Even if workable, people like yourself would just drive faster between 'breaks' to make up for the delay.

Yes, and?

Everyone has a perceived "max" they dare go over the 70mph limit. To think for one minute raising it to 80 would mean people wouldn't then apply their logic to the faster limit is naive at best.

That's assuming people break the speed limit because they think they can get away with it, rather than because the speed limit feels silly. Do you really think if the limit was 90 everybody would suddenly be doing 100+?

Face facts – we don't have a decent police force (in terms of manpower) to crack down on tailgaters, bad drivers, middle lane hoggers.

So instead of doing something for road safety, just make it look like you are with speed limits? 🙄