Spanish drivers are less than impressed with a "temporary" reduction of the maximum speed limit on motorways from 120 to 110 km/h, which came into force today as a measure to reduce petrol imports by five per cent a year. Speaking to RTVE, a disgruntled motorist summarised: "It's a joke, they're winding us up." An octogenarian …
They had it better than us...
...and now they're about the same. 110kph is 68.35mph, i.e. very close to 70, the highest national speed limit in the UK. If it's good enough for us then it's good enough for them. Besides, everyone here behaves like the normal limit is 80 anyway, I hardly expect Spaniards to do anything different.
"Besides, everyone here behaves like the normal limit is 80 anyway,"
In effect it is, as far as your car's speedometer is concerned.
Firstly guidelines state that you can't be nicked until you are doing 10% + 1mph over the speed limit. Secondly most car speedos overread by a few percent anyway, this is because the law allows them to overread by up to 10% (I think that's the right figure) but does not allow them to underread at all. So they are built to overread by a few percent to cover the manufacturer's arse. Ever noticed how your sat nave shows a lower speed than your speedo?
The end result of all this is that if you are driving at an indicated 80mph you are likely to be doing less than 78mph and are unlikely to be nicked where the speed limit is 70mph. Also, to the general horror of Daily Express readers, the police have got better things to do with their time than pull over motorists who are doing a couple of mph over the limit.
You can be nicked for doing 10% over, and people often have been, however, if you do get nicked then arguing in court that your speedo showed you on the button then the case could be dismissed (on the grounds that this is "reasonable") however the police could insist on a calibration test, which if it finds that you're over reading by 10% instead of under reading by 10% (as you're claiming) then you'll not only get a larger fine but you could also be done for perjury, if your spedo is underreading by up to 10% that's within legal limits - You'd be very unlikely to get away with more than about 5%, but it has been used to keep a licence for 101mph which otherwise would have resulted in an automatic ban (empty road, dry conditions, good light, well maintained car, clean licence), 6 points £300 fine, some would say "result".
You can use a speedo that underreads (i.e. in itself that's not illegal), however, it must not have been "constructed" to underread (Road Vehicles Regulations 1986), so if it's faulty or the wheels or tyres have been changed since construction (larger obviously) then it is a valid defence, at this point the defence will rest on what is, or is not reasonable, i.e. is the car well maintained (current MOT), were you overtaking everybody else, did you change the wheels and tyres or did you buy the vehicle second-and like that.
It's also a common misunderstanding for the legal limit for over-reading; it's not 10% it's 10% + 6.25mph. so if it's reading 80mph you could be going 67.
"the police have got better things to do with their time than pull over motorists who are doing a couple of mph over the limit."
Damn right, that's what the speed cameras are for.
Think yourselves lucky: in France it's €90 and 1 point off for going 1kph over the limit in the vicinity of a lurking cam.
You got a 70mph speed limit?!?
/me is envious; I still live under the Nixon-era 55 mph limit... :-(
"Think yourselves lucky: in France it's €90 and 1 point off for going 1kph over the limit in the vicinity of a lurking cam."
That is worse than here, we have a 5% tolerance which isn't much in a 40 zone (2Km). We just had a report that over 3/4 of fines issued (3500 every day) are for the most minor catagory of speeding.
There is little to do with "safety" in this scam, it is pure revenue raising.
So why all the thumbs down?
Lots of Spaniards reading this?
... If it's good enough for them then it's good enough for us.
I'll take that as a yes.
"This argument is unlikely to cut much ice with F1 driver Fernando Alonso, who was quick to criticise the new limit and warned it was so low that drivers could nod off from boredom, with fatal consequences."
Err - what?
Maybe they shouldn't be on the road if they are within a couple of kph of "dropping off from boredom"
Heaven help them if they ever get to a town, city, corner, traffic jam - anything that requires them to drop their speed by more than a few furlongs per fortnight...
Have you ever driven on a motorway or do you not get the concept of appropriate speed for the road?
70mph on an open motorway is boring.... through the middle of town isn't!
Well that explains it, all together now:
"Fernando...is faster....than YOU!"
Fernando Alonso was talking sense. I was a lorry driver at the time speed limiters became mandatory on HGVs. Before, the speed limit was 60Mph and my custom was to go everywhere at 100Kph...62.5 Mph in other words. At 62.5 Mph a lorry behaves differently to one that is restricted to 55Mph (the restrictors were meant to limit the lorries to 56, but 55 or 54 wasn't unusual.
The slower speed was boring enough to be dangerous. In fact I left lorry driving after a couple of close calls due to this very fact.
Drivers who spend a lot of time on the road have their reflexes and everything 'tuned' to a particular speed. Knocking 10Kmh off that speed is going to change the ground state of all those drivers to "bored out of their faces". And that's dangerous.
You want boring...
Try driving round and round and round in tiny circles for hours and hours of a sunday
now THATS boring.
So boring I'd be inclined to have an underling crash into a wall just behind me... to aleviate the boredom you understand.
I'm 100% with jezzas suggestion that they run on TG's test track, its an 8. prolly going to be the least boring race since turbo/ground effect days. (before the playsation generation moved in)
Fatigue and speed: the facts
Sleep Related Crashes account for about 25% of all fatal motorway accidents, rising to about half of all crashes (A roads and motorways) during the small hours.
(“Road Safety Research Report No. 52, Sleep-Related Crashes on Sections of Different Road Types in the UK (1995–2001)” ).
All speed factors together are a contributory factor for 14% of all motorway casualties (RCGB2008).
The factor of 'exceeding the speed limit' is generally 1/3 of all the speed factors.
There is clear scope for benefit by increasing motorway limits, not for reducing them.
Added to that is the displacement from/to less safe roads - a 'pull' towards motorways (the safest type of road) can only be a good thing. Reducing motorway limits 'pushes' traffic onto less safe roads, resulting with an overall increase of casualties across the road network (as well negating any supposed reduction of consumption).
Then there is respect for law. Making limits even less reasonable is a step in the wrong direction.
Lets put this in perspective
The new limit is just shy of 70mph, the (theoretical) limit on British motorways. If they clocked you doing 170kph on British roads, you'd most likely lose your licence, rather than get away with 2 points and a fine.
I'm not sure whether this makes a better argument fro raising British speed limits, or lowering the Spanish ones. To be fair, I doubt either would make any difference to the speed people actually drive at when there are no patrol cars around.
"What difference is there between driving at 120 or 110?"
Sounds like a stupid argument to me. If he really thinks there's no difference between driving at 68mph and driving at 74mph, then he's got nothing to whine about. If, OTOH, he thinks it is a problem then he needs a different argument.
There is difference
The difference is about 4miles per gallon for any of the cars in my household. 110 vs 120 is 46 vs 42 mpg.
Probably more for most "urban runabouts" for which 120 km/h and onwards is 3.5K+ rpm which means that you can kiss the fuel economy bye bye as they are designed to be fuel efficient till around 3.2-3.3. My Daihatsu definitely opens a ravenous mouth at 3.5 and starts gulping fuel dropping to as low as 32mpg on LPG/40mpg on petrol in winter.
If you drive it at less than that it is barely sipping fuel so you can easily go up to 50+mpg.
The UK 70mph motorway limit was originally imposed as a means to save fuel during some fuel crisis or another. So we've all been there. The question is, will the Spaniards limit ever be raised again? Don't hold your breath guys.
The limit was introduced in 1965, purportedly because of a number of accidents in fog, though rumours still abound that it was because AC Cars were using the M1 as a test track at up to 180mph.
IIRC, it had nothing to do with a fuel crisis.
Erm, not quite
I think you will find the 70MPH limit was introduced for 2 reasons.
To reduce the number of serious accidents with people travelling at very high speeds.
To stop manufacturers (for example Jaguar) testing new cars to the limit on the public roads.
Sadly, it works ...
Many years ago, I used to whizz around 80-90mph from London to Bath, and fill up at the other end. I had a 1L car, and it used to cost me just over a tenner. Then one Easter, it was just sheer weight of traffic - I couldn't get above 50 ... all the way.
When I filled up, it was just over £7 ... a damn near 30% increase in fuel efficiency, just by going 50 instead of 90.
Never forgotten that lesson ... which is why I get c. 44mpg from my 2.2L diesel, while in-laws are lucky to get 25 from their 2.0L diesel ....
mph and mpg
When my partner lived in Newcastle, she'd travel to see me at about 80mph. She'd get about 40mpg. I'd do the trip in the same vehicle, at 60mph, using other traffic as wind-breaks, and get >65mpg. Speed may not 'kill' as much as it used to, but it certainly has a greater cost!
Time is money, friend.
Do you value your time or your money more?
Back-of-the-envelope calculations and some precendts
At 110/120km per hour on a level road, the drag due to air resistance is the dominant force to be overcome. The drag will go up roughly to the square of speed, and this means the power required goes up as to the cube. Of course you are travelling for a proportionately shorter period of time, so the reduction in power required will be about 16%. Of course there is also rolling resistance (which is more like a linear relationship), so the actual power requirement reduction is less than this.
Roughly spekaing, you could reasonablyt expect an approximately 10% reduction in fuel usage for a given distance on flat ground by travelling at 110km/hr instead of 120km/hr. Of course there will be a considerable mileage which is not on motorways, but an overal national reduction of 5% sounds achievable.
Those with a long memory will recall the US introducing a blanket 55mph (88 km/hr) national speed limit in reaciting to the 1974 oil crisis. Given the appalling road traffic accident rate in the US these days, then they might want to consider re-introducing it (in the '70s US road traffic accident rates were comparable, or better then the UK's - now they are much worse, about 3 times higher per head of population twice as high per passenger mile).
The UK government introduced 60mph speed limits on dual carriageways and 50mph on non dual carriageways for the same reason (motorways remained at 70). However, these restrictions were removed much quicker than the US measures.
I have a 2.0L AWD petrol turbo nutter Subaru Forester and I can get over 30mpg on a motorway run at around the UK speed limit.
25mpg from a Diesel is shocking, what are they driving? A JCB?
What happens when you put multiple tortoises on the road?
Here's a question: what happens when *everyone* drives slower?
On one hand, everyone could improve their MPG - and reduce wear/tear on their vehicle - the engine isn't worked as hard and tyre wear should be reduced. Lower speeds may also reduce the frequency/severity of accidents, too, as people will have more time to react.
On the other hand: cars will be spending more time on the road - they'll physically occupy a given stretch of road for longer.. Roads have a fixed capacity, so this is likely to lead to increased congestion and traffic jams, especially during peak traveling hours. Which in turn could increase pollution and the risk of vehicle failure (e.g. cars sitting stationary and overheating).
There's also a number of other potential side effects - there's a small but potentially critical increase in both personal and commercial costs; the individual spends longer driving, which increases fatigue and the risk of road-rage and aside from the delay to goods delivery (esp. since truck drivers have to abide by the clock), people travelling for work will have to schedule more "dead time" inbetween activities, reducing their effectiveness - and the company may end up paying for this directly if it's an organisation which treats business travel as working hours/TOIL.
All told, has anyone ever done a study of the side-effects of changing speed limits? I know Top Gear recently did a smug "toldyouso" piece on the removal of speed cameras, but they're not exactly the least biased or most scientific observer available!
On a vague tangent: one place I'd love to see the stats for would be the A14 around Cambridge. They originally had yellow-box photographic cameras scattered along the road's length; these were then disabled for a few months while they installed a set of average speed cameras.
The road was PITA when the photo-cameras were in place, as many drivers stuck to an imaginary "60mph" speed limit until they were clear of the stretch, causing vast queues to form behind them. Things seemed to drastically improve when the cameras were disabled, and then went instantly downhill when the new cameras were activated - with the added bonus that driver stress levels shot through the roof due to the need to keep glancing down at the speedo...
Re: mph and mpg
"Using other traffic as wind-breaks"... Aka slip streaming when on the race track, or tail gating when on a public road?
So what rep-mobile do you drive?
What a long post
to miss the point ...
Internal combustion engines (whether by design, or physics, I don't know) have their maximum efficiency around 3000-4000 rpm. If you look at your speedo, in top gear, you'll find that 3,500 rpm is roughly 55 mph ... which is where you get maximum fuel efficiency.
Drag does play a part, but it's relatively trivial at those speeds.
Re: Sadly it works
Yup, just proved that over this weekend. Had to do a 600 mile round trip this last weekend and actively worked at keeping the speed in my Land Rover at 55mph. The result was 36mpg as opposed to around 30mpg. What's more, it was pretty relaxing, not tensing up to overtake, compete with, stare down and generally not behaving as aggressively as speed often make us behave.
Interestingly and on another topic, we stayed with friends who have a Lexus hybrid, and he was saying he can't get more than 31mpg....
What happens when everyone drives a bit slower.
Often the overall traffic flow goes up. Non-linear effects produce surprising results, y'know.
Also, if you really find it stressful to both have to look around you and occasionally glance down at the speedo, you need to go and get yourself some refresher lessons, since it's a pretty basic part of the skills you need for driving. Turning the wheel and pushing the pedals with your feet is the easy bit, anyone can do that; the skill in driving all comes from situational awareness and using it to guide your decision making.
Sorry, but technically speaking, you are what's known as somebody who hasn't got a clue. I'll make a guess now that you barely made GCSE science, but I'd happily swap physics qualifications.
As to the optimum thermodynamic efficiency of an engine. Well that depends on the fuel it uses, the efficiency of combustion and all sorts of other things. It's certainly not the case that car diesel engines are most efficient at anytthing like 4,000 RPM (mine Focus diesel will be a bit of 2,000 RPM). In any event, it's completely irrelevant. Cars are supplied witrh gearing systems for very good reasons, and one of those is to allow an engine to run at a reasonably thermodynamically efficient RPM and power output at a given road speed. However, optimising the thermodynamic efficiency is only part of the equation - the other issue is reducing the energy required to overcome resistance. That can be done through things such as reducing rolling resistance (e.g. by higher pressur tyres, reducing car weight) and drag. The latter can be achieved by improving aerodynamics, but also by reducing speeds, and at 70MPH air resistance is the dominant factor.
Typically modern cars reach their optimal duel efficiency on flat roads at about 55mph.
an incredible generalisation
My 2.0L Touran does ~1800 rpm at 55mph, At 3500 rpm its more like 110 mph.
Sorry but your calculations are rubbish, first we must assume that most people in this country drive diesels and not petrols (I believe the number of new cars sold in the uk is now about 80% diesel). Diesel engines have a much lower rev range than petrol and most redline at about 4-4.5k rpm and would "cruise" somewhere between 2k and 2.5k. My diesel Saab happily sites at 80mph at just over 2k rpm. Petrols on the other hand tend to rev much higher, usually about 6.5-7k and depending on gearing they would be doing 80mph in the 3k-3.5k range. My petrol Volvo does 80mph at 2.7k, so how you get 55mph at 3.5k i don't know as I believe most cars would be in 3rd gear to get that response.
The most efficient way to drive a car on the motorway is to go as slowly as you can in top gear while still maintaining the torque of the engine i.e. not at the point of stalling but at a point where you can accelerate away in top gear.
So I agree with you that it is usually somewhere in the 50-60mph range.
If 3500 rpm in 5th gear is only giving you 55 MPH what exactly are you driving?
Pretty much every petrol car I have owned with 5 gears does around 80MPH at 3000 rpm
Paris, high revving and whines a lot
The capacity of a road varies according to the average speed of the traffic on the road. That's why when the number of drivers on the road increases, the average speed comes down. I believe that it has something to do with the distance between cars reducing as the average speed comes down so you can fit more cars per mile of road.
As far as the A14 is concerned, I've found that driving on the Cambridge->Godmanchester stretch is slightly less frightening since they switched on the average speed cameras. That said, the road is an abomination and short of digging it up it's hard to imagine how the new cameras that are being installed will improve it.
Increased traffic density at lower speeds
As you should increase the gap between cars with speed (at least in proportion to speed, arguably more), then the increase in car density balances out the slower speeds. Of course once the traffic density hits a certain level then the flow becomes unstable, but generally a motorway with cars travelling at 50mph will allow for greater carrying capacity than one at 70mph. That is the ostensible reason for variable speed limits on some parts of the M25.
It's my experience that traffic is travelling slower on motorways, not just because of congestion, but due to a desire to save money on fuel. Indeed it's more than that - with modern asbestos-free brakes, the wear on disks means that heavy braking can lead to heavy maintenance costs. I think I've seen considerably fewer drivers on motorways relying heavily on their brakes.
Overal UK fuel consumption is down a lot over the past decade or so, some of which is down to changed driving habits.
Actaully, it is perfectly possible to benefit from slipstreaming without in fact tailgating.
A valuable lesson
So - Bath to London in 2hrs 20 minutes for £7 or 75 minutes for £10? A valuable lesson indeed - drive faster and you save a lot of time for only a small increase in fuel used.
Thanks a lot - I'll put that into practice!
Paris - 'cos her time is valuable too.
Is of course completely different depending on what vehicle you drive. The type of fuel, gearbox, and size are all important factors. Those figures might work for you but intelligence is required on the part of the driver to work out what is best for them, the vehicle and their goals.
The USA accident rates have nothing to do with raising the speed limit back to 70 mph. In actual fact, the accident rates in 1997 following the lifting of the 55 mph restriction were the lowest since the late 70s. (It's the same seemingly counter-intuitive effect of speed cameras in the UK).
Having lived in the UK for 30 years, and having driven all over Europe, my own opinion of the US accident rates is that skill level of US drivers is generally appalling by northern European standards. USA drivers have always had terrible lack of situational awareness, being distracted by eating, putting on makeup, shaving, whatever. On one one recent trip across the desert on I-10, I saw some idiot in a pickup lifting dumbbells ffs (namesake, no doubt).
The advent of higher levels of in-car technology has only exacerbated the situation. Lowering the speed limits won't pull people's heads out of texting, Facebook, or their collective asses (arses if you prefer).
My 'even more turbo nutter' 250bhp Saab does about 32/33mpg at 80mph.
Paris, 'cos she goes further on less juice.
*Yes - I do try to find the Paris angle with every post I make.
Maybe it's just diesels
but in my aged 2.0 straight-6 petrol I normally get just over 400 miles (so say 650km) to an 80 litre tank on dual carriageways/motorways (70-80ish mph). That's 22.3 miles per gallon. Which is piss-poor, I'll admit, but hey- it just means that I can buy a big V8 without worrying about mpg figures...
On the same road going at 40mph (on a space saver) I used almost exactly the same- 1/4 a tank in ~100 miles. I'll admit the needle was probably inside the marker rather than outside it so it wasn't utterly useless, but to be honest I'd rather spend an extra couple of quid and get home in half the time.
However, when I went out for a drive a few months ago (after a special on eco-mentalist driving, I guess) I had to dodge and weave between waves of people driving at 50 or 60mph. Speed up, slow down, speed up, slow down- I needed to fill up again after only about 300 miles. A massive, marked difference.
So I think all these "she only got 40mpg, but I got 65!" style comments don't just reflect the speed you're travelling at- they also reflect your driving style. If she's racing back to see you, Bonnie Tyler blaring, avoiding slower cars on the multilane roads and overtaking on the single-track roads but your just lazily cruise along singing along to Radio 4 you've got two totally different driving styles.
Yes, yours is better for fuel economy. But adopt your more laid-back driving style at 80mph and you'll soon see that your speed is making a lot less difference than you thought.
Golf TDI Mk5 3,000rpm is 90mph in top gear. It's not the best MPG I can get from that car ...
What's with all these numbers and shit?
I want some lazy car-IT analogy to make the argument clear for me.
Your cars peak efficiency is at 56mph, so you'd have done slightly better going slightly faster there.
Course, an hour ride at 90 or a close to two hour ride at 50mph, for £3 difference, I'm going to be £3 lighter.
save time.. do the maths
I drive too fast, cos i like it, my car is thirsty as a result, and I accept this, (square law of wind resistance and all ) .
But do not tell me you get there any quicker by doing so! it is simply not the case.
my sat nav smugly estimates my TOA on any journey, and it is always pretty much smack on.
I am often minded to drive like a headcase to beat it, the best i can recall beating it by was about 3 minutes....... in a 5 hour journey.
Let me introduce you to calculus.
now consider traffic speed/congestion as a second order function.
at peak times the vast majority of road users are travelling WAY below the speed limit
there fixed it for you
Your assessment is wrong. You neglect breaking distance. It has a non-linear relationship with speed. The faster a vehicle travels the greater the space that is needed around it. Throughput is increased by reducing speed - the optimum speed for throughput bearing the breaking distance issue in mind is about 40MPH. This is why the variable limits on the M25 work to clear congestion, reducing the speed limit as the road gets busier increases traffic throughput.
If your car is doing 55 mph @ 3000 rpm you NEED TO CHANGE GEARS!
I remember that retarded speed limit. I used to live in the US back then, and wondered why the hell did the US have such a slow-ass speed limit. Given US distances, it meant that most trips were a multi-day affair.
110 km/h is the standard speed limit in Mexico, but cops will only go after you if you go over 120 km/h.
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