Micro The Maniac wrote: ↑
Sat Sep 18, 2021 09:13
ajuk wrote: ↑
Sat Sep 18, 2021 00:36
You seem to be alluding to the hypothesis that if you set the speed limit lower than many or most drivers will only only drive X amount over or under the posted limit.
I have to admit I used to assume that to be true, but it's not by a long chalk. That claim has come to be like nails down a chalk board to me, so I wrote a blog
post about it.
I'm sure I've mentioned elsewhere the case study of a rural road near me... it was a self policing national speed limit road - self policing in that it twists and turns across the heathland. It is mostly perfectly driveable at approaching 60mph, slowing as needed for the bends. Unfortunately two cars, in quick succession, failed to take one of the bends, hitting the same sturdy tree... six teenagers were killed.
It should be noted that in both cases, the estimated impact speed was in excess of 100mph... at night, in the wet. And alcohol was a factor.
The idea is; some people are breaking the law, and the solution is to criminalise the behaviour of people not breaking that law, in order to stop people breaking that law.
The immediate cry of "something must be done" has resulted in the road getting a 30mph limit, with regular policing when it was still high in people's memory. Quite a few people were been done for 33.
It should also be noted that, with most cars obeying the limit, the numpty (sorry!) drivers still drive like idiots (sorry!).
As an aside, the 30 limit is now mostly treated with the contempt it deserves by most drivers... and the local plod have better things to do than sit on a country road with low traffic levels. They are dealing with the more populist issues, like guarding protesters.
I'm reminded of this section of this video
. "If you only ticked more afternoon commuters, those stupidity induced late night teen fatalities would never have happened
Sounds to me like that crash was already down to people driving dangerously and recklessly, that's not the people who will slow down because the limit has been made lower, they're the least likely to do so. People don't drive too fast because the speed limit lets them or because it's only slightly over the posted limit.
It sounds like the road into Cheddar, it was reduced from NSL to 30 because it's popular with drifters. They're notorious for their speed limit obedience.
Getting to over 30 down there is a mission for most people, I certainly wouldn't have argued to have a 40 limit along there, just no signs encouraging a speed
, but now there's no longer a 30 limit for traffic entering Cheddar.
pjr10th wrote: ↑
Sat Sep 18, 2021 21:58
My point isn't that a lower signed speed limit will magically immediately lower the speed of all drivers. My point is that the average driver has a tendency to slightly overspeed but not a tendency to underspeed. If you have a 30mph speed limit, near to noone will travel at 20mph if the road is clear ahead. In fact you'll get a fair few who will travel at 40mph+, while if you have a 20mph limit, you will get some drivers who will sit at 20mph, especially if it's enforced.
The key point should be national consistency, so drivers know what speed limit to expect for the road they're on. And 20mph should be the appropriate limit on the majority of urban & village streets, with the exception of the main motorist roads on your network (main roads which also don't have high place value, such as shopping streets or streets in the city/town centre). 40mph should only be used where frontal development is limited and there are low numbers of pedestrians and cyclists, e.g. the London North Circular (but even some of that should be 30).
No, that's not true, drivers overwhelmingly
judge their speed by the design of the road and the conditions at the time not
by speed limits.
I know of many 40 limit roads in South Gloucestershire that have lower average and 85th percentile speeds than a near by 30 limit road of a similar design.
You can have road that has a seemingly generous 40 limit lined with repeaters reminding people they can go 40 but the average speed is consistently in the low 30s and the level of compliance over 90%! Why? Because more people were parking on it the 40 limit road than on the 30 limit one and there were houses on both sides. The 40 limit do more warn pedestrians of the greater road danger, than they do to speed up traffic.
Yes, they do look to measure free-flowing average speeds for these surveys.
Yes, this sort of thing initially surprised me too.