A13, millions spent, limits now lower

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Truvelo
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Post by Truvelo »

That letter pretty much sums up what we knew all along - they want us out of our cars by making driving unpleasant.

The second paragraph, starting with "The link between lower speeds...." is total bull.

The next paragraph is the same. The private accesses were there when it was 50mph and there used to be more accesses before it was GSJd.

A 50mph limit is normal for an urban/semi urban GSJ dual carriageway so I can say bull to that argument as well.

In fact I can rubbish all the claims made in that letter. You only have to see the traffic to see what people think of the 40mph limit.
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Post by firefly »

Taking drugs effects just yourself (apart from smoking in public places). Driving too fast endangers everyone around you. You see it makes sence.
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Post by scynthius726 »

firefly wrote:Driving too fast endangers everyone around you.
It does. But you can't draw a line on a particular speed and say everyone on one side is safe and everyone on the other side is dangerous. Speed cameras (which they support) cannot make this distinction. A trained police officer can.
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Post by mixsynth »

A reduced traffic speed is considered to greatly improve the environment for walkers and cyclists.
That's it. That's your reason. They want to "encourage walking/cycling over use of the private car"; in other words, they want to p**s drivers off who use the road.

This is surely misuse of speed limits at its worst.
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Post by signol »

mixsynth wrote:
A reduced traffic speed is considered to greatly improve the environment for walkers and cyclists.
That's it. That's your reason. They want to "encourage walking/cycling over use of the private car"; in other words, they want to p**s drivers off who use the road.

This is surely misuse of speed limits at its worst.
Exactly, especially as a motorway-esque road, I doubt many pedestrians or cyclists use it. Is there an alternative? As for safety, the current situation probably makes it less safe, with driver irritation leading to rash decisions and the frantic braking at speed cameras.

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mixsynth
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Post by mixsynth »

My issue is that speed cameras were sold to parliament and the public as "safety" cameras. They're being used here to enforce someone's opinion of a nicer environment for people nearby.

Words fail me.
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Post by ndp »

Truvelo wrote:That letter pretty much sums up what we knew all along - they want us out of our cars by making driving unpleasant.

The second paragraph, starting with "The link between lower speeds...." is total bull.
No it isn't. It may be a bit simplistic, it may omit that its a balance (you never have perfect safety, you have a balance between utility and benefit), and it doesn't in itself justify the 40mph limit - but I don't think its fair to describe it as "bull"
The next paragraph is the same. The private accesses were there when it was 50mph and there used to be more accesses before it was GSJd.
Maybe the limit was wrong before?
A 50mph limit is normal for an urban/semi urban GSJ dual carriageway so I can say bull to that argument as well.
Not ones with significant numbers of at grade LILO junctions (at least IME).
(I assume there are no gaps in the central reserve?)
In fact I can rubbish all the claims made in that letter. You only have to see the traffic to see what people think of the 40mph limit.
IMV that letter raises a series of valid reasons why that limit may be sensible. Now I don't know the road, so I don't know if these reasons exist on the ground - but given what evidence I have seen (ok, which isn't enough for a proper assessment of the limit) doesn't really prove the limit to be inapparopriate.

I would suggest one mistake has possibly been made, which is it seems the road hasn't been designed to make the limit self enforcing. If 40mph is a suitable limit (again I haven't seen evidence to prove it isn't). Perhaps slightly narrowing the lanes would have been helpful (though I should point out that that I don't know if any measures along these lines were actually considered or implemented).
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Post by PeterA5145 »

ndp wrote:Now I don't know the road, so I don't know if these reasons exist on the ground - but given what evidence I have seen (ok, which isn't enough for a proper assessment of the limit) doesn't really prove the limit to be inapparopriate.
You may not think me the most impartial judge, but I can assure you having used the 40 mph section of the road that it is certainly of a general standard and configuration that pretty much anywhere else in the country would be 50 mph, and if built twenty or more years ago might even originally have been NSL. There are 50 mph roads of considerably inferior standard within a few miles (parts of the A12 and the North Circular).

I seem to recall Serena also agreeing that 40 mph seemed too low, and she's no boy racer ;)

If most drivers choose to do well about 40 mph, it does rather suggest the limit is wrong.
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Truvelo
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Post by Truvelo »

Well said Peter. The only reason I can see for the 40mph limit is Ken Livingston and the junctions would still be traffic lights if he had become mayor before construction started.
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Post by firefly »

scynthius726 wrote:
firefly wrote:Driving too fast endangers everyone around you.
It does. But you can't draw a line on a particular speed and say everyone on one side is safe and everyone on the other side is dangerous. Speed cameras (which they support) cannot make this distinction. A trained police officer can.
Of course you can draw such a lign. Considering safety concerns, fuel consumtion, noise and exhaust gas pollution as well as time consumtion of motorists on the other side there is a bandwidth of speed where benefits are greater than costs. And to keep motorists within this bandwidth speedlimits are required.
Police officers are just the executive authority and speed cameras are their tolls. The only distinction they make is have you violated a speed limit or not.
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Post by ndp »

firefly wrote:
scynthius726 wrote:
firefly wrote:Driving too fast endangers everyone around you.
It does. But you can't draw a line on a particular speed and say everyone on one side is safe and everyone on the other side is dangerous. Speed cameras (which they support) cannot make this distinction. A trained police officer can.
Of course you can draw such a lign. Considering safety concerns, fuel consumtion, noise and exhaust gas pollution as well as time consumtion of motorists on the other side there is a bandwidth of speed where benefits are greater than costs....
Of course, there are other issues on the faster-limits side as well, such as consistancy of limits, ensuring limits are limits and not targets, and maintaining confidence in the system, but the principle is right - its a balance.

That said, it is important not to become to dependant on limits and enforcement - limits are nothing without enforcement, and there is only so much enforcement that can be done feasibly. The aim should be getting drivers to choose to drive at an appropriate speed. Limits, cameras, education and engineering all have a role to play, but none of those would work on their own.
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Post by highwaymana31 »

Truvelo wrote: The second paragraph, starting with "The link between lower speeds...." is total bull.
The remainder of the first sentence reads "The link between lower speeds and reduced injury accidents is well established."

And you say that is total bull, please explain
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Post by PeterA5145 »

highwaymana31 wrote:
Truvelo wrote: The second paragraph, starting with "The link between lower speeds...." is total bull.
The remainder of the first sentence reads "The link between lower speeds and reduced injury accidents is well established."

And you say that is total bull, please explain
You can start with this.

Plus this - scroll down the page to "the one mph lie".

The problem is that the claim presupposes nothing else has changed, whereas to achieve a reduction in speed, something must have changed, so you are not in the same situation as before.

Also, as a generality, faster roads are safer. Clearly they are faster because they are safer, not the the other way round, but if you make roads "slower" by in effect increasing the degree of risk then it does not follow at all that they will become safer.

Also consider the following from Simonet & Wilde on risk homeostasis:
Due to the inevitable uncertainty of the outcome of any given action, the human brain has learned to optimise its degree of psycho-physiological arousal. A lower than optimal arousal would reduce our readiness to deal with a sudden threat; a higher than optimal level would soon exhaust our nervous resources. Physical risk, therefore, cannot be removed with impunity from the traffic system by a massive lowering of legal speed limits or any technical intervention aimed at the same effect. Such measures would be expected to produce a reduction in alertness and, hence, induce a state of behavioural adaptation to new conditions which is less capable of dealing with unexpected threats. A major decrease in the traffic accident rate per capita would, therefore, remain doubtful. If coercive speed reduction were successful in curtailing speed, this would likely amount to reversing the historical trend and thus lead to a reduced road mobility per head of population and a higher accident rate per kilometre driven.
If you could comfortably type at 70 wpm, and you were told that under no circumstances must you exceed 50 wpm, you would almost certainly make more mistakes.
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Post by ndp »

PeterA5145 wrote:
highwaymana31 wrote:
Truvelo wrote: The second paragraph, starting with "The link between lower speeds...." is total bull.
The remainder of the first sentence reads "The link between lower speeds and reduced injury accidents is well established."

And you say that is total bull, please explain
You can start with this.

Plus this - scroll down the page to "the one mph lie".

Of course, lower speeds to mean reduced injuries in the event of an accident - and this may more than offset an increase in accidents as a whole.

The homeostasis point is a valid one, and forms part of the balancing arguments for higher limits.

Nevertheless, I do feel that Truvelo's somewhat childish dismissal of the points raised in the letter to be rather unhelpful and indeed counterproductive. The issue of poorly set limits will not be solved as long as the debate is drowned out by hysterical ranting from minority groups on both sides.

As I said, I don't know the road. My point was merely that the arguments put forward in the letter for the lower limit were valid considerations. Whether or not the balance is for a 40 mph limit, I don't know.

I'd also be interested to hear what people think the limit should be, and why....
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Post by Bryn666 »

I'd say a 50 limit would probably be better, as people would presumably drive at about 45-50mph anyway, whereas a 40 limit will simply be broken.

Perhaps this is further evidence that we need much more flexibility with the setting of speed limits - in America I strongly suspect the A13 would have a 45mph speed limit. That would appear to be a happy compromise.
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Post by Truvelo »

I don't mean to cause offence but I'm only stating the facts.

One of the points mentioned on TFL's letter is the lower the speed limits get as you get further into London. If this is so then I propose the following:
70 where it present starts at Dagenham
50 between Ripple Road and Canning Town
40 between Canning Town and the westen portal of Limehouse Tunnel
30 west of Limehouse Tunnel.

The Lodge Avenue will have to be 40 but I can't see why it couldn't be 50 either side. Anyone scraping the underside of their car on the flyover will remember not to go so fast over it next time. The section to the west can't be compromised because of this.
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Post by PeterA5145 »

ndp wrote:Of course, lower speeds to mean reduced injuries in the event of an accident - and this may more than offset an increase in accidents as a whole.
Lower impact speeds mean reduced injuries in the event of an accident, but there's no automatic relationship between free travelling speeds and impact speeds - hence all the fatalities in 30 limits from accidents involving vehicles travelling within the speed limit. If lower free travelling speeds are achieved at the cost of eroding driver attention, then they may have no effect on impact speeds. Indeed I have seen figures indicating that the average severity of injury accidents is greater in 20 limits than 30s, suggesting a fairly severe erosion of driver attention.
Bryn666 wrote:Perhaps this is further evidence that we need much more flexibility with the setting of speed limits - in America I strongly suspect the A13 would have a 45mph speed limit. That would appear to be a happy compromise.
Allowing x5 limits alongside x0 limits would tend to reinforce the misleading view that if only we could find exactly the right speed limit for a road, its safety problems would be solved. A speed limit is by definition a very broad-brush tool and people shouldn't be encouraged in the view it can be applied (or indeed should be enforced) with precision.
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Post by firefly »

PeterA5145 wrote:Lower impact speeds mean reduced injuries in the event of an accident, but there's no automatic relationship between free travelling speeds and impact speeds - hence all the fatalities in 30 limits from accidents involving vehicles travelling within the speed limit. If lower free travelling speeds are achieved at the cost of eroding driver attention, then they may have no effect on impact speeds. Indeed I have seen figures indicating that the average severity of injury accidents is greater in 20 limits than 30s, suggesting a fairly severe erosion of driver attention.
It is rather the greater fragility of traffic participants on streets where a 20 mph limit is applied than the attention of drivers.
I have never seen a study that concludes higher speed limits increases road safety. And I doubt that you can show me a serious one that does exactly that.
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Post by PeterA5145 »

firefly wrote:
PeterA5145 wrote:Indeed I have seen figures indicating that the average severity of injury accidents is greater in 20 limits than 30s, suggesting a fairly severe erosion of driver attention.
It is rather the greater fragility of traffic participants on streets where a 20 mph limit is applied than the attention of drivers.
Most 20 mph areas are no different in general characteristics to nearby 30 mph areas.
I have never seen a study that concludes higher speed limits increases road safety. And I doubt that you can show me a serious one that does exactly that.
Plenty of evidence that re-engineering roads to permit higher speeds makes them safer, though. The safest roads are generally those with the highest average speeds.
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Post by ndp »

All this gets the "I haven't seen the road in person, I'm working on what is here and photos" disclaimer.
Truvelo wrote:I don't mean to cause offence but I'm only stating the facts.
They weren't the facts, it was personal opinion. Contrary to popular opinion, these are not the same thing ;)
Truvelo wrote: One of the points mentioned on TFL's letter is the lower the speed limits get as you get further into London. If this is so then I propose the following:
70 where it present starts at Dagenham.
Seems resonable.
Truvelo wrote: 50 between Ripple Road and Canning Town
.
.
The Lodge Avenue will have to be 40 but I can't see why it couldn't be 50 either side. Anyone scraping the underside of their car on the flyover will remember not to go so fast over it next time. The section to the west can't be compromised because of this.
The trouble is that if the limit were to go up to 50 on the western side, it is likely that a significant number of vehicles would pay little attention to the brief 40 limit over the flyover. Enforcement simply wouldn't be practical due to the nature of the flyover. So what could you do about about people who take the flyover too fast? What about the ones who crash first time they take it too fast? What about those who get away with it the first time and get cocky because of it?

Granted, people aren't obey the existing 40 limit. But I very much doubt that they would obey a 50 limit either, and at least some people would reckon they could get away with a bit faster than they do at present.

Additionally, the divided footway/cycleway shown at http://sunilprasannan612.fotopic.net/p18999234.html is rather narrow. I think it would be questionable to permit traffic to travel at 50mph given that.
Truvelo wrote: 40 between Canning Town and the westen portal of Limehouse Tunnel
30 west of Limehouse Tunnel.
AIUI, the Limehouse link has a poor alignment, and presumably significantly poor visibility at the junction within the tunnel. Given this and the general vulnerability of tunnels (you really, really don't want an accident in a tunnel), the I'd suggest the 30 limit through there is appropriate.

I'd suggest similar may be the case through the East India Dock tunnel.

TBH, I do think they have got the limits right.
PeterA5145 wrote:
Bryn666 wrote: Perhaps this is further evidence that we need much more flexibility with the setting of speed limits - in America I strongly suspect the A13 would have a 45mph speed limit. That would appear to be a happy compromise.


Allowing x5 limits alongside x0 limits would tend to reinforce the misleading view that if only we could find exactly the right speed limit for a road, its safety problems would be solved. A speed limit is by definition a very broad-brush tool and people shouldn't be encouraged in the view it can be applied (or indeed should be enforced) with precision.
I am inclined to generally agree with that (though I do think strict enforcement is sometimes appropriate).

Perhaps ideally the section between East India Dock and Lodge Avenue would be 50 for this reason - but you'd be relying on people realising the need to slow down and to do it without being told. At the moment I don't think we can put that much faith in people.
Firefly wrote:
PeterA5145 wrote: Lower impact speeds mean reduced injuries in the event of an accident, but there's no automatic relationship between free travelling speeds and impact speeds - hence all the fatalities in 30 limits from accidents involving vehicles travelling within the speed limit. If lower free travelling speeds are achieved at the cost of eroding driver attention, then they may have no effect on impact speeds. Indeed I have seen figures indicating that the average severity of injury accidents is greater in 20 limits than 30s, suggesting a fairly severe erosion of driver attention.
It is rather the greater fragility of traffic participants on streets where a 20 mph limit is applied than the attention of drivers.
I have never seen a study that concludes higher speed limits increases road safety. And I doubt that you can show me a serious one that does exactly that.
20mph zones do consistantly show that will fatal accidents go down after implementation, but injury accidents go up. This is due to risk compensation - pedestrians feel safe due to the relatively slow speed of vehicles, and thus don't feel as much of a need to look. Accidents can result.

Additionally, it can also be shown that excessively low limits reduce driver's trust and compliance in the limit system, and that lower limits can cause an increase in speed (people will comply more with limits they perceive to be reasonable, even if their own judgement would tend to a higher speed than the limit). Ultimately, if motorists start losing confidence in the limits system, they'll simply ignore the limits - and ignored limits may as well not be there.

On the other hand, we also have reasonable limits which are not percieved to be reasonable. This is why it is vital speed limits are set appropriately high, and that unreasonably low speed limits are rooted out. Afetr all, we do (and always will) rely on drivers being willing to obey limits, and for that to happen at locations where the limit is rightly set but lower than the percieved approriate speed drivers need to be able to trust limits. And they can't do that while we have the 70mph motorway limit, or Oxfordshires excessive use of 50 limits etc.

Maybe higher limits don't increase road safety - but excessively low limits can certainly seriously damage it
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