Safe Speed Forums

After reading these forums for the last month or so I have decided to join and make my first post.

Riding home this evening on a three lane dual carriageway at the 30-40mph limit on a motorcycle capable of 145mph I suffered the usual attention wandering that driving at an artificially low speed can cause.

Strangely enough though (or maybe not), my mind wandered to the subject of speed limits themselves. I had some thoughts that will be pretty hard to put into words, and may well be total rubbish, but I am going to post them anyway.

If I understand it correctly, then good engineering principles state that the speed limit for any road should be set at 85% of the average natural free flowing traffic speed.

If we then take the Brunstromian definition of speeding as being to exceed the posted speed limit by 10% + 2mph (I will even ignore the extra 2mph) then if my understanding is anything like correct then on average, in a correctly and safely set speed limit, 93% of drivers should never get a speeding ticket.

The converse of this that if every speeding driver was caught and prosecuted, then again on average 7% of the driving population would have speeding convictions.

The point when more than 7% of the driving population have speeding convictions must be some kind of critical moment. What it means though, I am not totally sure of, but let us look at this some more.

We know that the percentage of drivers who speed and are caught is a lot less than 100%.
We also know that a lot more than 7% of the driving population have convictions for speeding.

Therefore it must follow that:

Speed limits are being set artificially low, ignoring the 85th percentile rule.

A large numbers of safe drivers are being convicted of speeding.

It would appear that drivers will continue to drive at what they consider to be the safe speed for the road regardless of the speed limit and enforcement by speed cameras.

Speed cameras are not working.

I have not thought too long and hard about this line of reasoning, but instead have just made this post when I got in from work while the idea was still in my head, so if it is total rubbish, try not to be too hard on me.



Biker-Russ

- Many speed limits are too low. But that's partly because they have to step in 10s. So if 50 would be too high then the speed limit must be 40. No chance of a 45 limit. Maybe even 48mph would be the safe speed. (In the USA they step in 5s, and the rest of the world uses km and steps in 10s which is steps of approx 6.25mph)

- They probably set them a little bit lower knowing that people will exceed them by a little.

- Many drivers will drive as fast as they can regardless of the speed limit. Most of the time they'll get away with it, i.e. they won't have an accident as a result.

- There are loads of accidents every day, of which about 17% are caused by directly speeding. Most of these are probably caused by "excessive" speeding (often dangerous driving).

- Speed limits can often be arbitrary because they do not allow for changes in road conditions, both weather related and conditions like rush-hour, school-times and shopping hours.

- Driving at an inappropriate speed is dangerous. Driving too slowly also causes a hazard and is therefore also dangerous. So while speed limits are not targets, it is preferable that you do not drive inappropriately slowly.

I'm not sure this is true. Undoubtedly a few will, if they can get away with it, but I think it's only a small minority overall. In Manchester, there are several wide, straight radial roads such as Hyde Road and Ashton Old Roads. They have 30 limits, perhaps some stretches would be OK for 40s in view of extensive demolition and clearance on either side, and most traffic probably travels at around 40 in clear conditions. You could easily do 60+ and stand a good chance of getting away with it, but very few do.

Most drivers tend to drive at a speed they feel comfortable with, rather than trying to maximise their speed as much as possible.


I think recent figures from a government report said the proportion of accidents where inappropriate speed was the primary cause was about 12%, of which about two-thirds were likely to be inappropriate speed within the posted limit.

Regards,

Peter

_________________
"Show me someone who says that they have never exceeded a speed limit, and I'll show you a liar, or a menace." (Austin Williams - Director, Transport Research Group)

Any views expressed in this post are personal opinions and may not represent the views of Safe Speed

Biker-russ, welcome to the world of common sense. Your musings have brought you to the very conclusions that SafeSpeed has been battling to get heard.


Kaz

Yes, but they probably think it's safe because they get away with it so often. They are a minority, but a large enough minority that you will encounter them every now and then, especially if you drive a lot (and I used to work as a mini-cab driver in London when I was between computing jobs).