[Talk-GB] Implicit speed limits: What to tag in built-up areas?

[David Woolley]

On 02/05/18 13:03, Craig Wallace wrote:
> A 20 sign with a green circle is advisory. A 20 sign with a red circle 
> is a legal limit.
> Some advisory limits are signed as "Slow zone" or similar.

Advisory signs can be put up with no formality.  Legal speed limits 
require a traffic regulation order, with the associated public 
announcements and public consultation periods.  That's the main reason 
you are likely to see advisory signs.

In another thread, on a different forum, this came up for cycle lanes. 
A lot of UK cycle lanes are advisory, meaning cars can park on them with 
impunity, so they are often of limited use.