Congestion on urban freeways is of two types—recurring and nonrecurring.
Congestion that occurs regularly at particular locations during certain time periods
is said to be recurring. On the other hand, congestion that occurs as a result of
irregular events, such as accidents, disabled vehicles, or other similar happenings,
is said to be nonrecurring. Both can cause driver dissatisfaction, but drivers usually
expect the recurring congestion and make adjustments in their travel plans to
accommodate it. The most common example of recurring congestion is the morning
and afternoon “rush hour” periods, when traffic demands can exceed the capacity
of the freeway.