I think rshdunlop's point about the bus (356) turning left from PV is valid - the problem it and the Clarke's coaches face do need some attention.

TfL's point on, "This would be the last opportunity they would have to turn off the A205 to avoid the low bridge just west of Waldram Place. However, from Perry Vale this bridge is not visible, and it is therefore likely that any instructions on these signs would not be followed. If drivers miss Perry Vale and are no longer able to use Waldram Crescent it would cause delays and difficulties on the network." is fairly specious.

There are two significant opportunities before a truck reaches WC -Perry Vale as mentioned but also Westbourne Drive. Number recognition systems work perfectly well in all circumstances including directive signs for low height warning systems and therefore "flash" signs can say "Driver of vehicle registration AA61 BBB must turn left now."

Additionally frequency of such occurrences is waning as commercial vehicles have SatNav systems with low bridges and clearances specifically marked and thereby route planning tends to avoid such problem circumstances.