Roger wrote:
In fact I think there are cases for both vehicle activated signs AND speed cameras, the latter a few tens of car lengths after the former, at certain specific places. however, these places really are few and far between.
Here's an example of where a clearly-marked camera (or indeed SPECS installation) might be appropriate. This is a hypothetical location, but very similar to some real-world ones I can think of.
There's a 40-limit village on a fast rural NSL A-road. It's in a dip, with a steepish climb out at one end, but the road is ruler-straight, so when entering the village you can see the NSL signs at the other end about half a mile away. There's a pub, church, shop, petrol station and about sixty houses, some of which are in a close turning off the main road. There's also a T-junction with a minor road near the village centre.
The highway authority have done all the things in their toolkit - erected prominent gateways saying "Little Snoring - Please Drive Carefully" under the 40 mph signs, put up speed-activated display signs that trigger at around 43, painted central hatching throughout the length of the village to make the road seem narrower, and built central refuges to prevent overtaking within the village limits.
The result is that average speed is about 35 mph, 85th percentile speed 43, which on the face of it seems like a good outcome. However, it is noticeable that about 2% of vehicles still pass through at over 60 mph, which, since there are 5,000 a day in each direction, is 100 a day. There have been a few crashes at the junction with the minor road which the police feel were at least partly due to excessive speed on the main road. Also, in one direction, a number of HGVs go through "on the limiter" as they wish to maintain momentum for the hill on the other side.
Every couple of months, the police have a blitz and pull over a number of offenders, but as this is done between the hours of 9 am and 5 pm on weekdays it fails to catch either the regular commuters or weekend leisure drivers/riders, so there is little effect on the level of offending.
Clearly the highway authority could kill the problem stone-dead by building a roundabout with a wide deflection in place of the T-junction, but the villagers might not appreciate the sound of HGVs grinding up and down the gearbox all day long. Might a camera be a better solution?
Regards,
Peter