Passenger load factor refers to how many people are on the bus at any given moment compared to its seated and standing capacity. While high productivity is desirable for transit service, passenger loads must be monitored to ensure that the service remains attractive to travelers. Comfort and access issues may result if overcrowding conditions occur, and additional service may need to be required to address the situation.

Passenger load factor is calculated by dividing the maximum load for a trip by vehicle seating capacity. A trip is overcrowded if load factor is greater than 1.25 (100% of seating capacity + 25% of seating capacity worth of standees) at any point during a trip.