Domestic drivers hours rules apply to the drivers' of Vehicles on journeys within the United Kingdom which are exempt from the EC rules.
The rules do not apply to drivers who always drive off the public road (i.e. driving in connection with road improvements or road maintenance, quarrying or other construction work or civil engineering works)

.A driver who drives for less than 4 hours in any day in any fixed week (24:00 hrs Sunday to 24:00 hrs Sunday) does not have to observe the drivers hours requirement during that week.

Daily Driving Limit - Domestic A driver must not drive for more than 10 hours in a day. The daily driving limit applies to time spent at the wheel actually driving on a public road. Off-road driving counts as duty time.

Daily Duty Limit - Domestic A driver must not be on duty for more that 11 hours on any working day. A driver is exempt from the daily duty limit on any working day when he does not drive.

Emergencies
The domestic rules are relaxed for events needing immediate action to avoid danger to life of health; serious interruption of essential public services (gas, water, electricity, or drainage); or of telecommunications and postal services; or in the use of roads, railways, ports, airports; or serious damage to property. In these cases the driving and duty limits are suspended for the duration of the emergency.