There is an option available for hauliers to request a special routing agreement. This allows for a new route to be agreed by London Councils that makes greater use of non-ERN roads than would usually be accepted.
This requires the haulier to make a compelling case that the proposed route is better in environmental terms than the standard compliant route. The usual measure of benefit is based upon the number of dwellings the vehicle will pass on its journey.
It should be noted that these agreements are rarely entered into (there are currently about 150 of them), that the criteria for them are quite strict and they are subject to regular review.