The provision lets you take your required 10 hours off duty as two periods instead of one unbroken block. It has three conditions, and all three must hold.
The three conditions
- One period of at least 7 consecutive hours in the sleeper berth. This one is restricted to the berth — off-duty time elsewhere does not count.
- Another period of at least 2 consecutive hours, off duty or in the berth, or a combination.
- The two periods together must total at least 10 hours.
Why 6+4 does not work
It totals 10 hours, so people assume it qualifies. It does not, because neither period reaches 7 consecutive hours in the sleeper berth. The total is necessary but not sufficient.
FMCSA is running a pilot programme that adds 6/4 and 5/5 splits — but only for enrolled drivers. It is not the general rule.
What happens to the 14-hour window
This is the real benefit. When a pair qualifies, neither period counts against the 14-hour driving window, and the window is recalculated from the end of the first qualifying period. That is what buys back driving time.
Order does not matter
Either period can come first. What matters is that one of them is the 7-plus hour berth period and the pair totals 10.
Source
Summarised from the FMCSA Summary of Hours of Service Regulations and the FMCSA 2020 hours-of-service FAQ set.