Long-haul truckers have to deal with some pretty rigid rules about when they can work, and perhaps more importantly, when to rest. Unfortunately, that may not always line up with how the day is actually going. The rulebook in question comes from the Federal Motor Carrier Safety Administration, or FMCSA, the agency that governs commercial driving across the US.

A driver can only stay on the road for so long before those rules require proper rest. Officially, the rulebook demands 10 straight hours off duty, taken in full before getting back behind the wheel. But the 7/3 split gives drivers some extra flexibility for how they spend their downtime.

Normally, a driver has to take ten hours off in one unbroken block. The 7/3 lets them chop it into two instead. So, one of those pieces has to be at least seven consecutive hours in the sleeper berth, while the other needs to be at least three consecutive hours.

The driver has the choice to pick how that goes — it can either be off-duty, in the sleeper, or some combination of the two. Stack those two together, and you land at 10 hours. The nice part is you can take them in either order, so maybe the three-hour break comes first, and the seven-hour stretch comes later — or the other way around. Both work fine. Either way, it’s the bunk is where most of that downtime is usually logged, so it is worth knowing what the inside of a semi truck sleeper cab looks like.

Since a commercial driver is actually juggling three separate clocks at the same time, there’s a number of ways the split can affect it. First is the 14-hour on duty window, which frames the working day. This is the daily span where the trucker has to finish all their duties – not just driving, but also loading, fueling, or otherwise representing a carrier in any official way.

The handy part is that time spent in the sleeper berth does not count against it. That is the whole reason the bunk has been worth its space ever since the first sleeper truck changed American trucking. So once both qualifying breaks are done, the window gets recalculated rather than being wiped clean. A full 10-hour break hands you a totally fresh start.

Next up is the 11-hour driving limit. This one acts as a cap for the number of hours actually spent rolling down the road in a day. Any drive time you had banked before the break does not vanish. It can be completed once you are moving again.

Then comes the 70-hour weekly limit. This is a running total of every hour across a rolling eight-day stretch that a driver spends working, similar to the on-duty window noted above. Once that total reaches 70 hours within an eight-day stretch, they cannot drive again until some of it frees up.

The catch here is that the split does nothing for this weekly total because it’s only geared towards a single day. It’s worth mentioning here that there’s a sibling to the 7/3 split known as the 8/2 split, which just shuffles the math to eight hours and two, though the underlying idea stays the same.