Plenty of drivers live in two legal worlds at once: a rigid truck on tachograph Monday and Tuesday, a 7.5-tonner under GB domestic rules Wednesday to Friday. The assimilated rules and the domestic rules do not take turns politely - they overlap, and the government’s mixed-driving guidance sets out exactly how. For operators, the mixed week is where hours compliance most often quietly unravels, because each set of rules sees the other set’s work differently.
Three principles govern the mixed day or week, and the first word is that the assimilated rules take precedence over the GB domestic rules. Time spent driving or on duty under the assimilated rules cannot count as a break or rest period under the domestic rules. Driving and other duty under the domestic rules - including non-driving work in another employment - counts as other work, not as a break or rest, under the assimilated rules. And driving or duty under the assimilated rules counts towards the driving and duty limits under the domestic rules. In short: everything counts everywhere, and nothing counts as rest anywhere it was not.
The domestic limits never sleep. The GB domestic driving limit - a maximum of 10 hours of driving in a day - must always be obeyed, as must the domestic duty limit of no more than 11 hours on duty in a 24-hour period. But whenever any assimilated or AETR driving is carried out, the assimilated duty picture applies too: a maximum duty spread of 13 hours, or 15 hours, determined by the amount of assimilated daily rest needed, and the assimilated breaks must be taken within those duty periods. The driver on a mixed day is therefore satisfying two frameworks simultaneously - the stricter of the two effectively governs the day.
Drivers who drive in scope of the assimilated rules must comply with the sector-specific working time rules, which carry the same rest requirements as the assimilated hours rules. The relief valve is the occasional mobile worker. Occasional mobile workers need only comply with assimilated daily rest requirements on days when they actually drive under the assimilated rules - but they must still take an assimilated weekly rest. So a driver who works under the assimilated rules one week and domestic rules the next must take a regular or reduced weekly rest in the week containing the assimilated driving, and a reduced weekly rest still demands compensation by the end of the third week following. Because nobody may work more than six 24-hour periods between weekly rests - including work not regulated by the assimilated rules - an occasional mobile worker whose domestic work would breach that must take a weekly rest before starting any assimilated-regulated work.
Record keeping follows the same dual logic. Working under the assimilated rules means assimilated record keeping always applies in addition to GB domestic record keeping - and that holds even for occasional mobile workers. On any day containing both assimilated and domestic driving, the driver must keep records under both sets of rules. Under the assimilated rules, all non-assimilated and non-AETR work - secondary employment included - must be recorded as other work, using an analogue tachograph chart, a digital or smart tachograph printout, or the manual input facility of a digital or smart tachograph. The assimilated rules also require records for rest days and for annual or sick leave. And when an examiner or police officer asks, the driver must be able to produce the assimilated records - including the driver card where held - for the current day and the previous 28 calendar days, together with any GB domestic records.
The fleets that handle mixed driving well treat it as a planning problem rather than a paperwork problem. Rota design matters: clustering assimilated-scope driving into clear blocks reduces the days where both frameworks bite at once. Driver briefing matters more: the driver who thinks Tuesday’s domestic van work “doesn’t count” toward Wednesday’s tachograph day has the rule exactly backwards - it counts as other work, it eats into the assimilated duty spread, and it must be recorded. And analysis must see both sides: a tachograph-only view of a mixed driver’s week misses the domestic hours that the examiner will ask about. The mixed rules are not obscure; they are simply strict - and strict rules handled systematically stop being a problem.