Summary of information received from Lewisham Council with percentage analysis by me:

Traffic was counted 'in the middle of Devonshire Road' - ie not where it would be slowed by queues.

The traffic count was undertaken from 26 June - 3 July 2009.

Total number of vehicles counted, 10449 northbound and 10538 southbound.

Northbound -
54.1%<20 mph, 94.5%<25mph, 99.4%<30mph. Just 5 vehicles (0.02%) over 40mph - and they could be counting errors. Mean speed 19.6mph with 85% under 22.8mph.

Southbound
36.2%<20 mph, 85.1%<25mph, 98.5%<30mph. Only 1 vehicle over 40mph - and that was apparently doing more than 60mph at around 8am so is almost certainly an error! Mean speed 21.2mph with 85% under 24.8mph.

My observation would be that most drivers are close to, or a little above the 20mph speed limit with drivers tending to speed more when travelling southbound. Bear in mind that speeds would have been measured at the fastest point in the road.

Very few drivers are doing more than 30mph and virtually none 'twice the speed limit'.

Banning the right turn into the South Circular would be a matter for TfL and would, apparently, require extensive consultation in surrounding streets. My limited observation is that few vehicles actually make this right turn but they cause chaos, and hazards, in doing so. The views of others on this would be very welcome.