Survey: Peak Occupancy Rate
The average peak hour occupancy rate at the maximum load point in the peak direction gives an indication of the adequacy of the service provided.
It is normally necessary to obtain this information by means of surveys.
The peak periods may not be precisely known: in any case determination of peak periods will be subjective to some extent. If the peak periods are not known, it will normally be appropriate to take a period of approximately four hours: in the morning, this should commence approximately three hours before the time at which the majority of people start work; in the evening it should commence approximately one hour before the time at which the majority of people finish work. When plotted as a bar chart, showing total passenger numbers at ten minute intervals, the period during which occupancy rates are highest may be identified as the peak. In most cities the morning peak is shorter and more concentrated (typically one to two hours) than the evening peak (typically 90 minutes to three hours).
Subsequent surveys may be confined to these peak times.
Surveys should be conducted in the direction of peak flow. This will normally be towards the city center in the morning, and away from the center in the evening. They should be conducted at the point on each route where loads are at a maximum: this should be determined by observation but will normally be near to the city center.
It is not possible to count the exact number of passengers on each bus as it passes, and it is necessary to estimate loads and capacities. It is normally sufficient to assess, for each bus that passes, whether it is empty, has a quarter, half or three-quarters of a seated load, a full seated load, a normal standing load, or is overloaded. From observation of a sample of buses, an approximate number of passengers for each of these load categories can be determined. If there are buses with significantly different capacities, these must be identified, and estimates made for each category of bus.
The survey form will have columns for each load category. Where there are different sizes of bus, there should also be a column for each; if there is only one size of bus, these columns will be unnecessary. If there are several routes, it is useful to identify these, and a column for route (or route number) should also be included.
As each bus passes the survey point, the surveyor should enter the time and route (or route number) in the appropriate column, and place a tick in the appropriate column for bus size and load.
The capacity of the service, and number of passengers traveling, may then be estimated for successive time periods: it is normally sufficient to take totals for fifteen-minute periods.
The peak occupancy rate is the total number of passengers, expressed as a percentage of capacity over the full peak period.
Where additional information is required, for example to determine the number of vehicles operating on a route, it may also be appropriate to include a column for bus registration or fleet numbers. It must be borne in mind that each additional column will require more time and greater concentration on the part of the surveyor, and on a very busy route there is a limit to the amount of detail that can be recorded by one person.
