Cycle campaigning

Some detailed opinion about 20mph 2000pcu here.

http://rachelaldred.org/writing/20mph-2000pcu-using-it-for-local-campaigning/

She highlights Hackney as somewhere where changes have been implemented that move towards that goal. Though I think it is important to realise that borough has not been dominated by campaigns for strict segregation, Rachel picks a good example of a road that has been freed up for bikes but car access has been restricted as somewhere where infrastructure is working.

Does this essentially mean of the 2000pcu 85% must be under the speed limit for it to qualify as succesful ?