Speed limit setting

[saaby93]

Tafia said:

It clearly doesn't fit the 85th percentile which is why it makes an ideal trap site.

85th percentile is only used in the rules for cameras not speed limits
Cameras can go in if a fair number of drivers are exceeding the 85th percentile & exceeding the speed limit
Speed limits use mean speeds instead and shouldnt be lower than those
Ask for the traffic speeds to find out if the limit is too low, if it is the camera shouldnt be there.

Lower speed limits are rarely best to reduce accident rates, you said theyd tried to change the junction to solve that problem.

[Tafia]

saaby93 said:

Tafia said:

It clearly doesn't fit the 85th percentile which is why it makes an ideal trap site.

85th percentile is only used in the rules for cameras not speed limits
Cameras can go in if a fair number of drivers are exceeding the 85th percentile & exceeding the speed limit
Speed limits use mean speeds instead and shouldnt be lower than those
Ask for the traffic speeds to find out if the limit is too low, if it is the camera shouldnt be there.

Lower speed limits are rarely best to reduce accident rates, you said theyd tried to change the junction to solve that problem.

I think it was Welsh Blackbird who mentioned a junction alteration which was perhaps a mile west of this trap site. There are no junctions on this stretch once past the entrance to St Melyd Golf CLub

I had understood that many authorities have used the 85th percentile speed as a guide when setting limits.

More here http://www.safespeed.org.uk/speedlimits.html

On the cameras information section of the N Wales speed trappers, they mention a list of features pertaining to each trap site but under " 85th Percentile" they seem to use the phrase; "No information available" a lot.

I wonder why?

[saaby93]

Tafia said:

I had understood that many authorities have used the 85th percentile speed as a guide when setting limits.

Nope that's out of date - it was superceded some years back to make it more 'understandable'. The limit shouldnt be lower than the speed most people are driving, (it will usually amount to pretty much the same thing)
http://www.dft.gov.uk/pgr/roadsafety/speedmanageme...
85%ile is only used for siting cameras

[Tafia]

saaby93 said:

Tafia said:

I had understood that many authorities have used the 85th percentile speed as a guide when setting limits.

Nope that's out of date - it was superceded some years back to make it more 'understandable'. The limit shouldnt be lower than the speed most people are driving, (it will usually amount to pretty much the same thing)
http://www.dft.gov.uk/pgr/roadsafety/speedmanageme...
85%ile is only used for siting cameras

Hmm. I wonder if they would tell us how many drivers have been speed trapped at the site pictured over the years. Since I saw the van at the other end of the stretch of road to where the scamera folks said it would be, I have spoken with several folks who have been speed trapped there, usually at around 35 to 36 mph.

[saaby93]

Youd be better off asking if the camera siting complies with the above Dft guidelines i.e. they'll need to show theyve first measured traffic speeds and checked the limit agrees with that.