What is the process for deciding speed limits? - dimdip
Can anyone tell me (or point me to a thread or website) how speed limits are set, please? I'm thinking more about the local process rather then the national limits; particularly roads that carry a 30 mph limit where that seems unreasonably low. Specifically, is someone with relevant technical knowledge involved, or is it decided by 'other factors'? Thanks.
What is the process for deciding speed limits? - Rhubarb
Try: www.dft.gov.uk/pgr/roadsafety/speedmanagement/dftc...f

It's a PDF document.
What is the process for deciding speed limits? - Honestjohn
I think this concerns the ludicrous lowering of the 40mph speed limit to 30mph on a dead straight road with very few entrances or houses between Hampton Court and Kingston. As soon as the camera van hides itself along this stretch most drivers will be sitting ducks. But if due warnings are laid out, as they are these days in Surrey, then it's difficult to see what possible justification there can be for it. Maybe someone has complained that traffic at 40mph upsets their horses. Maybe there was an 'incident' as the result of the newly laid down bicycle lane.

HJ
What is the process for deciding speed limits? - movilogo
I think it is the threshold point where people will become frustrated at ludicrous low limit inappropriate for the road and then they will start to flout it - so that it will generate revenue via speed camera/traps etc.

What is the process for deciding speed limits? - FocusDriver
Second HJ's post about H'Court to Kingston. There is an example of illogical road management likely to lead to frustration if ever there was one. Safety cameras continue to be located where they shouldn't be and omitted from where they'd do some good.
What is the process for deciding speed limits? - Mr X
'What is the process for deciding speed limits?'
In one word - Politics
What is the process for deciding speed limits? - dimdip
Thanks for the replies. Although I wasn't concerned with a particular road, the one HJ mentions is just the scenario (and good grief that must be an interminable drive now at 30 mph; it felt slow enough at 40!).

Agreed movilogo; as the document that Rhubarb kindly linked to states: "Indeed, if a speed limit is set in isolation, or is unrealistically low, it is likely to be ineffective and lead to disrespect for the speed limit." It seems clear that this aspect of the guidance document is not being adhered to in some cases.