# Speed limits?



## redddraggon (17 Jun 2010)

What's the point having a Wide, well surfaced, good visibility main road with a 50mph speed limit, and then having the narrow, poor visibility, poorly surfaced, country lanes off the main roads at the national speed limit?

Seems a bit stupid to me - should they not be 20 or 30mph limits?


----------



## RedBike (17 Jun 2010)

Speed limits don't reflect the 'safe' speed limit.
After all they rarely change when the road has a dangerous corner etc. 

They are more to do with the roads location / proximity to a built up area.

I would like to see dynamic speed limits introduced on motorways and some 'A' roads. 

Heavy rain / fog - drop the speed limit to 40mph. 
Clear carridgeway at night. - Lets have a 100mph limit.


----------



## jazzkat (17 Jun 2010)

lots of stuff about speed limits here
http://www.safespeed.org.uk/speedlimits.html

the problem is so many people choose to drive at whatever speed they think is right. Not helped by local councils lowering speed limits on roads that are well surfaced and capable of higher speeds causing motorists to become frustrated. Once youve broken that law its easy to break it again IMHO.


----------



## jonesy (17 Jun 2010)

jazzkat said:


> lots of stuff about speed limits here
> http://www.safespeed.org.uk/speedlimits.html
> 
> the problem is so many people choose to drive at whatever speed they think is right. Not helped by local councils lowering speed limits on roads that are well surfaced and capable of higher speeds causing motorists to become frustrated. Once youve broken that law its easy to break it again IMHO.



There's certainly lots of bollox on that web site.

I'm unclear why the 'frustration' of drivers who wish to go faster than they are allowed to should prevail over the wishes of those who'd like a safer, more civilised environment on their streets...


----------



## Bromptonaut (17 Jun 2010)

jonesy said:


> There's certainly lots of bollox on that web site.
> 
> .



+1


----------



## wafflycat (18 Jun 2010)

jazzkat said:


> lots of stuff about speed limits here
> http://www.safespeed.org.uk/speedlimits.html
> 
> the problem is so many people choose to drive at whatever speed they think is right. Not helped by local councils lowering speed limits on roads that are well surfaced and capable of higher speeds causing motorists to become frustrated. Once youve broken that law its easy to break it again IMHO.



As pointed out, there's a complete load of bollox on that site. Please don't drag safespeed over here. If I may remind we motorists who hold a full driving licence, it's a basic driving skill we have to demonstrate competency in in order to obtain said licence: driving within the speed limit at all times. If someone really has difficulty in doing that then they should stop driving solo and not do so again until they've had some remedial training to bring their driving skill back up to the level of basic competency. It's really not at all difficult to drive within the limits.


----------



## guitarpete247 (18 Jun 2010)

I used to have a 70 mile Drive down the M1 on Friday and back North on Sunday which I usually did at 80mph+. When I slowed down to 70mph I realised that: 
a) It was taking me the same time for the journey give or take 10 mins;
 I was saving myself a hell of a lot of fuel;
c) I enjoyed the driving more as I wasn't so stressed over other numpties coming up behind flashing me as they had to be somewhere fast (probably needed the loo or something like that).

Drove down to Cornwall a few years ago with a trailer full of camping gear. Instead of 35 mpg I got 52mpg just by sticking to 60mph (the limit for a trailer).


----------



## StuartG (18 Jun 2010)

Yes, yet another outstanding example of a graduate from the Dr Andrew Wakefield School of Statistical Inference.


----------



## Rhythm Thief (18 Jun 2010)

I drive from Mitcheldean (near Gloucester) to Hemel Hempstead every night, mostly in an artic but sometimes in a 7.5 tonner. In the artic I'm limited to 40mph for most of the stretch between Gloucester and Oxford, in the puddlejumper I can drive at 56 mph on the same stretch. It makes maybe ten minutes' difference to a three hour journey. Hardly worth bothering about. My colleague does the same journey every night and he's forever telling me how he has to watch out for cameras, slow down when he sees a pair of headlights in his mirrors "in case it's a copper", and so forth. Who needs that?


----------



## al78 (20 Jun 2010)

redddraggon said:


> What's the point having a Wide, well surfaced, good visibility main road with a 50mph speed limit, and then having the narrow, poor visibility, poorly surfaced, country lanes off the main roads at the national speed limit?
> 
> Seems a bit stupid to me - should they not be 20 or 30mph limits?



Because the wide, well surfaced, good visibility road has hidden hazards on it that may not be immediately apparent to drivers who are not familiar with the road. The hazards on the narrow, poor visibility, poorly surfaced, country lane, on the other hand, are so obvious to the driver that the hazards act as a natural speed limiter (think risk compensation).

The most dangerous roads are the ones that look perfectly innocuous, but have a nasty surprise at an unlucky moment.


----------



## Bad Company (28 Jun 2010)

RedBike said:


> Speed limits don't reflect the 'safe' speed limit.
> After all they rarely change when the road has a dangerous corner etc.
> 
> They are more to do with the roads location / proximity to a built up area.
> ...



Excellent idea.

Could be difficult to police tho.


----------



## atbman (29 Jun 2010)

Renminds me of the Top Gear bit a few years ago. They tested the difference between two drivers (B'ham - Exeter), one of whom lane hopped whenever the lane he was in was going faster. T'other stayed in lane.

The difference at Exeter was 5 minutes quicker for the lane hopper


----------



## gavintc (29 Jun 2010)

atbman said:


> Renminds me of the Top Gear bit a few years ago. They tested the difference between two drivers (B'ham - Exeter), one of whom lane hopped whenever the lane he was in was going faster. T'other stayed in lane.
> 
> The difference at Exeter was 5 minutes quicker for the lane hopper



Personally, I always get lane hopping wrong and end up pushing in to an even slower lane. I now tend to sit it out - less stressful.


----------



## JamesMorgan (30 Jun 2010)

There is a potential personal dilema as highlighted by the safe-speed website. The speed at which the lowest crash risk is approx at the 85 percentile. So if, as an individual, I want to drive at the safest speed for me I should typically drive at that speed. However, if I did have an accident at this speed the consequences for a pedestrian or cyclist would be a lot worse. So I need to resolve the dilema of my own personal safety with that of others. I think this is where enforced speed limits really come in. There has been a lot of recent discussion about dropping residential speed limits to 20mph. If I drove at 20mph today the chances are I would be more likely to have an accident, but if I did hit a pedestrian/cyclist they would probably survive. If the speed limit was enforced at 20mph then my own chance of an accident would probably not go up.


----------



## Bad Company (30 Jun 2010)

JamesMorgan said:


> There is a potential personal dilema as highlighted by the safe-speed website. The speed at which the lowest crash risk is approx at the 85 percentile. So if, as an individual, I want to drive at the safest speed for me I should typically drive at that speed. However, if I did have an accident at this speed the consequences for a pedestrian or cyclist would be a lot worse. So I need to resolve the dilema of my own personal safety with that of others. I think this is where enforced speed limits really come in. There has been a lot of recent discussion about dropping residential speed limits to 20mph. If I drove at 20mph today the chances are I would be more likely to have an accident, but if I did hit a pedestrian/cyclist they would probably survive. If the speed limit was enforced at 20mph then my own chance of an accident would probably not go up.



Mr Paul and the other usual suspects will be along shortly.


----------



## Dan B (30 Jun 2010)

JamesMorgan said:


> There is a potential personal dilema as highlighted by the safe-speed website. The speed at which the lowest crash risk is approx at the 85 percentile.


Given safe(sic)speed's usual ability with figures, I am willing to bet this is a confusion between correlation and causation.

And what anyway is the 85th percentile speed in a typical urban 30? The cars may be moving at 25-30, the bikes at 12, the pedestrians at 4 and the street furniture at 0: any and all of these are entitled to be on the road and are potentially hazards that the driver must respond to. So "going at the same speed as everyone else" is a meaningless concept


----------



## jonesy (30 Jun 2010)

coruskate said:


> Given safe(sic)speed's usual ability with figures, I am willing to bet this is a confusion between correlation and causation.
> 
> And what anyway is the 85th percentile speed in a typical urban 30? The cars may be moving at 25-30, the bikes at 12, the pedestrians at 4 and the street furniture at 0: any and all of these are entitled to be on the road and are potentially hazards that the driver must respond to. So "going at the same speed as everyone else" is a meaningless concept



It is simply bollox of course. JamesMorgan won't be able to provide any research supporting his claim that the 85%ile is the safest speed at which to drive, because there isn't any. If he looked at the research (by which I mean real research, carried out using robust methods and subject to peer review) he'd see that lower speeds reduce both the probability and severity of crashes, full stop, which is why 20mph zones are successful at reducing causalities:
http://www.bmj.com/cgi/content/full/339/dec10_3/b4469.


----------



## JamesMorgan (1 Jul 2010)

Just to be clear, I am not claiming that 85%ile is the safest speed - just pointing out that if it is perceived to be by other drivers then it does create a personal dilema between individual safety and safety of others. I have no idea whether the research quoted on safespeed re the 85%ile safety stands up to peer review. However, from personal experience I do know that driving at a slower speed to the 'normal' traffic flow is potentially dangerous and can cause accidents. I do sometimes do it to save fuel, but it is stressful and does require more concentration. I could unilaterally decide to drive at 20mph in built up areas. Although this speed would be safer to pedestrians/cyclists, I personally prefer to drive at 30mph (unless road conditions dictate otherwise) as I believe it to a speed less likely to cause accidents. The only solution to overcome this is to have an enforced 20mph speed limit.


----------



## adscrim (1 Jul 2010)

JamesMorgan said:


> Just to be clear, I am not claiming that 85%ile is the safest speed - just pointing out that if it is perceived to be by other drivers then it does create a personal dilema between individual safety and safety of others. I have no idea whether the research quoted on safespeed re the 85%ile safety stands up to peer review. However, from personal experience I do know that driving at a slower speed to the 'normal' traffic flow is potentially dangerous and can cause accidents. I do sometimes do it to save fuel, but it is stressful and does require more concentration. I could unilaterally decide to drive at 20mph in built up areas. Although this speed would be safer to pedestrians/cyclists, I personally prefer to drive at 30mph (unless road conditions dictate otherwise) as I believe it to a speed less likely to cause accidents. The only solution to overcome this is to have an enforced 20mph speed limit.



Who is actually to blame is you driving at 20 mph resulted in an accident? Is it not the responsibility to of those around you to drive with due care and attention? I know you're just being theoretical but if Driver B is involved in a crash because of frustration caused by Driver A's lower speed, then Driver B is at fault- no?


----------



## Bad Company (1 Jul 2010)

> All it does cause is the occasional idiot on my bumper. They don't bother me at all.



They should. They are bloody dangerous.

I had an HGV do that to me a while ago. I was keeping the 30 limit thru a village on the way to work and I guess he wanted to maintain his momentum. He was flashing his lights and all sorts. Very intimidating and very dangerous.


----------



## skrx (1 Jul 2010)

JamesMorgan said:


> I could unilaterally decide to drive at 20mph in built up areas. Although this speed would be safer to pedestrians/cyclists, I personally prefer to drive at 30mph (unless road conditions dictate otherwise) as I believe it to a speed less likely to cause accidents.



Accidents isn't the same as injuries, and I reckon that driving at 20mph on a 30mph limit road, causes less-severe injuries overall, even if the number of accidents is larger (which it may or may not be, I don't know. Most of the time I'm in 30mph areas I'm being followed by cars going at less than 20mph and it doesn't seem to be a problem).


----------



## Bad Company (2 Jul 2010)

> HGVs maybe, yes. But I'm not too bothered about an idiot ramming me up the chuff with the likely small speed differential. They'll be the ones paying after all. And, again other than trucks, I don't really find them intimidating.



As I said you should be bothered because it's dangerous. If you have to stop quickly and the bloke behind you can't you can receive a whiplash injury or worse still he can push you into the danger.

Example - You are driving at or below the limit with a another car a couple of feet from your rear bumper. A child runs into the road and you hit the brakes stopping just short of the child. The car behind cannot stop, runs into the back of you and . . . . .

Not much you can do about it though.


----------



## adscrim (2 Jul 2010)

> HGVs maybe, yes. But I'm not too bothered about an idiot ramming me up the chuff with the likely small speed differential. *They'll be the ones paying after all*. And, again other than trucks, I don't really find them intimidating.



Assuming they have insurance!


----------



## Bad Company (2 Jul 2010)

adscrim said:


> Assuming they have insurance!



A brave assumption imo.


----------



## al78 (4 Jul 2010)

Bad Company said:


> As I said you should be bothered because it's dangerous. If you have to stop quickly and the bloke behind you can't you can receive a whiplash injury or worse still he can push you into the danger.
> 
> Example - You are driving at or below the limit with a another car a couple of feet from your rear bumper. A child runs into the road and you hit the brakes stopping just short of the child. The car behind cannot stop, runs into the back of you and . . . . .
> 
> Not much you can do about it though.



Ultimately, you have no control over other people.

In the scenario you describe, it is highly likely the child will escape with minor injuries since if the driver behind shunts you into the child, you will hit the child at a very low speed (<10 mph).


----------



## GrasB (4 Jul 2010)

Actually what's more likely to happen is you hit the brakes, get down to 10-15mph then have the car behind hit doing 5-10mph more than you pushing your speed back up again & extending your braking distance a fair way as you foot will most likely be jerked off the brake by the impact.

This is why I got into the habit of using the fly off handbrake as well as the foot brake when doing an aggressive braking/emergency stop. While the effect brake on braking was minimal under normal condition the natural action of a rear impact would be to pull the handbrake on harder which would help compensate for the reduction of foot brake input. Well that was the theory anyway, I never found out if it really worked or not.


----------



## GrasB (4 Jul 2010)

I wasn't arguing about keep the speeds up regardless. I was more giving a good reason why it isn't just speed limits that need to be enforced but also dangerous driving by tailgating needs to be addressed as well. It also illustrates why when you're being tailgated you need to extend your estimated stopping distances.


----------



## Nigel-YZ1 (6 Jul 2010)

The enforcement of road standards by totally mechanical means has led to the belief that slowing people down will stop all the evils of the world.

Keep the cameras running - doesn't bother me, but can we finally get some eyes on the road to deal with the bigger dangers too?

We have a generation that KNOWS that they are immune as long as they slam on the brakes at the little yellow boxes. So the one-handed driving, slouched, handbrake-turning, farty exhausted, drunk, drugged, uninsured, tailgating, gross-speeding, bullying, chance-takers only have to obey one law for 25 yards at a time, and god help the rest of us.


----------



## jazzkat (6 Jul 2010)

I've not looked in here for a while, I seem to have stirred up a hornets nest linking to safe speed. Apologies.

I don't agree with the politics of the site, it was the 85 percentile thing (I googled) It is one of the things that stuck in my mind about setting speed limits. Whether its true or just the motoring lobby's take I know not, but it did stick in my mind.

My take on speed is that you must be in control of your vehicle and be able to stop in the distance you can see to be safe. Not as easy as you think and painfully slow in many circumstances. Try it the next time you are out driving, you will be surprised, even on the bike there are a few descents in 30 limits where I can easily get up to 30 and I know if a car came out of a side road I'd be toast. I do it because I ride very early in the morning in a very small rural town, no excuse, but no different from many motorists. We take the risks WE perceive to be ok and some people are less risk averse than others.

The only real answer is for everyone to take regular retesting to a higher standard than the current test. A few years ago I took my IAM test and was surprised and pleased in equal measure about the quality of my motoring. Everyone should have to do it, combined with a police force that is actually able to enforce the laws we have on the statute books, I reckon we could have one of the best and safest road networks in the world IMHO


----------



## JamesMorgan (7 Jul 2010)

jazzkat said:


> I don't agree with the politics of the site, it was the 85 percentile thing (I googled) It is one of the things that stuck in my mind about setting speed limits. Whether its true or just the motoring lobby's take I know not, but it did stick in my mind.



Like you, I'm not sure about the 85 percentile research but intuitively it feels right. However, all this means is that in order to travel safely, you should be travelling at a similar speed to the rest of the traffic. The purpose of speed limits (and more importantly enforcing them) is to determine what that speed should be. Drivers are not always a good judge of what a safe speed is, especially if it on a stretch of road unfamiliar to them. Unfortunately having inappropriate speed limits (esp too low ones) leads some drivers to believe that speed limits are not useful and to ignore them in all situations. Whilst safespeed seems to draw conclusions from this that it is better to set speed limits at the speed that most drivers want to drive, I suspect a more useful conclusion is to force drivers to drive at the speed that is optimised for safety.


----------



## StuartG (7 Jul 2010)

JamesMorgan said:


> Like you, I'm not sure about the 85 percentile research but intuitively it feels right.


I would refer the learned gentleman to my earlier post on Safespeed:

_Yes, yet another outstanding example of a graduate from the Dr Andrew Wakefield School of Statistical Inference._

If you can't see the illogicalities in the proposition for yourself than forgive me it will be pointless to waste further time ... just as pointing out simple facts to the JABS people was a waste of time. Meanwhile needless lives were lost & damaged.

You do appear here as a troll.


----------



## JamesMorgan (7 Jul 2010)

StuartG said:


> I would refer the learned gentleman to my earlier post on Safespeed:
> 
> _Yes, yet another outstanding example of a graduate from the Dr Andrew Wakefield School of Statistical Inference._
> 
> ...



I'm sorry, but I can't see how drawing a comparison between accidents caused by traffic moving at different flow speeds and some discredited research on vaccines has any relevence. If you have some research that counters my inituitive view that travelling at a similar speed to the rest of the traffic flow is safe then I welcome it. 

By the way, a 'troll' is normally someone who posts outrageous comments in order to bait people for an answer. They will typically use insults and are rarely interested in providing any real discussion around the main topic area. I think your response is a classic example.


----------



## StuartG (7 Jul 2010)

JamesMorgan said:


> By the way, a 'troll' is normally someone who posts outrageous comments in order to bait people for an answer. They will typically use insults and are rarely interested in providing any real discussion around the main topic area. I think your response is a classic example.


My dear friend - look back - I think you will find my comment was one of the rather more restrained responses.

If you want a serious discussion then you need a serious proposition. The arguement that travelling at 85% is the safest _within a peloton_ of traffic is clearly independent of the safest average (or maximum) speed for that peloton. There is also the obvious illogicality that if you restrict people travelling faster than the 85 percentile - then you shift the percentiles down until you are all stationary.

The safest speed is a little more difficult to determine than the simpleton argument propounded by Safespeed. Is that insult or fact?


----------



## JamesMorgan (7 Jul 2010)

StuartG said:


> My dear friend - look back - I think you will find my comment was one of the rather more restrained responses.
> 
> If you want a serious discussion then you need a serious proposition. The arguement that travelling at 85% is the safest _within a peloton_ of traffic is clearly independent of the safest average (or maximum) speed for that peloton. There is also the obvious illogicality that if you restrict people travelling faster than the 85 percentile - then you shift the percentiles down until you are all stationary.
> 
> The safest speed is a little more difficult to determine than the simpleton argument propounded by Safespeed. Is that insult or fact?



I think you will find that these were all points previously made by me, so I am somewhat confused as we appear to be in agreement. My argument was that in order to achieve a safe driving speed at 20mph we first need to enforce a speed limit of 20mph. I don't support restricting driving faster than the 85th percentile - as you say it is mathematically unachievable anyway. You seem to feel that I am in some way supportive of the Safespeed website, when my messages seem to indicate the contrary. I have just happened to use some of the research on their website about accident rates and speed differentials. Whatever we think about Safespeed there does appear to be quite a lot of evidence that speed differentials are a major cause of accidents (as is inapproriate speed).


----------



## JamesMorgan (7 Jul 2010)

> In my experience (and I have a history with safespeeding) it's very dangerous to take any notice of their "evidence".
> 
> Unless you think that, for example, sitting in your car in a garage with a stopwatch and looking out of a window to determine the distractive effects of a speedometer is credible evidence. That was one of the most outlandish examples, but even his interpretation of other people's proper figures is worthless.



I suspect you are right - esp. in the way that their conclusions are drawn from various items of research. However, regarding the 85th percentile there does appear to be quite a broad amount of evidence around accident rates. What I hadn't realised until I just googled it, is that many countries (including the UK and US) do currently set speed limits based on the 85th percentile. This does appear to lead to the slighty crazy approach that you can't set a lower speed limit than the 85th percentile. You first have to lower speed (through measures such as road calming), then once the 85th percentile has fallen you can lower the speed limit. I don't think this applies in 30/20 mph zones though.


----------



## StuartG (7 Jul 2010)

The whole fallacy of the Safespeed idea is that because there is an inherent danger in speed differentials then we should let motorists manage the speed and keep up with an unlimited pack. This is ludicrous nonsense. They then falsely (and from reading the rest of the site I suspect knowingly) translate danger into safety policy. 

Within it own deranged world it is rubbish. It equates a crash at 20mph with one at 80mph. Whether passenger, cyclist or pedestrian - those pose very, very different risks/outcomes.

The site is one (and this is why I mentioned JABS) that take an idea which may or may not be true in itself and with an agenda not based on evidence seek to extend it well outside its limitations to befuddle, confuse and get their agenda promoted while ignoring or even discrediting all the hard and non-controversial evidence to the contrary.

This really annoys me. And why I, amongst others here, will shout baloney when we see it. And have our suspicions about those that continue to give it credence.


----------



## JamesMorgan (7 Jul 2010)

StuartG said:


> The whole fallacy of the Safespeed idea is that because there is an inherent danger in speed differentials then we should let motorists manage the speed and keep up with an unlimited pack. This is ludicrous nonsense. They then falsely (and from reading the rest of the site I suspect knowingly) translate danger into safety policy.
> 
> Within it own deranged world it is rubbish. It equates a crash at 20mph with one at 80mph. Whether passenger, cyclist or pedestrian - those pose very, very different risks/outcomes.
> 
> ...



OK - I now know where you are coming from, and am broadly in agreement.


----------



## StuartG (7 Jul 2010)

JamesMorgan said:


> OK - I now know where you are coming from


Keep checkin' those mirrors dude


----------



## wafflycat (7 Jul 2010)

jazzkat said:


> My take on speed is that you must be in control of your vehicle and be able to stop in the distance you can see to be safe. Not as easy as you think and painfully slow in many circumstances. Try it the next time you are out driving, you will be surprised,




Well no, I wouldn't be surprised. Not because I'm a brilliant driver but because it's a *basic* motoring skill of the sort those of us who have a full driving licence had to demonstrate competency in in order to pass the test to gain that full licence. 

I'm constantly shocked, by those of us who have full licences, at the excuses made for poor driving when it's *basic* skills not being talked about. What is it amongst too many of us driving that once we've passed the test and got the full licence that means basic skills go out of the window or are deemed somehow difficult to do? It's as if once passed the test basic skills, competencies and rules no longer apply or are suddenly too difficult to do.


----------

