On 2011\10\30 16:21, Nick Finnigan wrote:
On 30/10/2011 08:03, Basil Jet wrote:
At the crossroads of Exhibition Road and Cromwell Road SW7, traffic
approaching from three directions is now banned from turning left or
right.
This is signified by the green light being a forward arrow. At other
junctions where both turns are banned you would see a vertical white
arrow
on a blue background beneath the three traffic lights, but they have not
done that here.

I would expect to see 'no left turn' and 'no right turn' signs in red
circles alongside or under the green arrow.

After a little googling, it seems that is the norm for forced forward
across a two way road (except Oxford Street, curiously), whereas the
blue arrow is the norm for forced forward because both side roads are no
entry. Perhaps the distinction is to help police cars etc. know that
it's okay to ignore the former but you have to be bloody careful when
ignoring the latter. I've always thought that there should be some
distinction between banned turn because of no entry and banned turn
because it's a banned turn, to help police cars driving at speed.