See the Order
This transferred responsibility for cleaning the section of the A40 east of J1 of the M40 (previously A40(M)) to the border with LB Hillingdon from S Bucks DC to the Highways Agency. The order includes similar transfers for other sections of highway
Interestingly the Explanatory Memorandum states
Monitoring & review
12.1 The monitoring of cleanliness will be conducted by the Highways Agency and is subject to the graded standards of cleanliness expected as part of the DBFO Operator contract and as defined in the ‘Code of Practice on Litter and Refuse’ issued in January 1991 and updated in November 2006 by the Secretary of State for the Department for the Environment, Food and Rural Affairs under section 89(7) of the Environmental Protection Act 1990.
12.2 The DFBO Operator is as far as reasonably practicable required to ensure roads are kept at a Grade A standard for paved areas and a Grade B (or higher) standard for verges and other soft areas. If this target is not met operators are obliged to meet the above standards within 28 days from Grade C and within 7 days from Grade D.