In addition to daily and work shift limits, drivers need to work within cycle limits of cumulative on-duty hours. Cycle limits help to prevent the fatigue that builds over time. When a driver reaches a cycle limit, the driver must stop driving. A driver can start a new cycle at any time if the driver takes an extended period of off duty time (as specified per rule set) that acts as a cycle reset.
Each cycle limits the number of on-duty hours in either a 7-day (Cycle 1) or 14-day (Cycle 2) period. On-duty time includes both driving time and On duty, not driving time. If a driver reaches the cycle limit, the driver must stop driving however, the driver can perform other on duty work as long as the driver does not exceed the daily and work shift limits.
At any time, a driver can end the current cycle and start a new cycle if the driver takes an extended period of off duty time that acts as a cycle reset as specified per rule set. During the cycle reset, the accumulated on duty hours are set back to zero hours. After the reset period, the driver starts a new cycle and the driver’s on duty hours begin to accumulate from zero again.
Ref: Alberta Motor Transport Association, Alberta Reference Guide for Hours of Service Training Development, June 23, 2008.