8.2Data Needs

Data is not information, information is not knowledge, knowledge is not understanding, understanding is not wisdom.Clifford Stoll, astronomer, 1950-

For any detailed traffic-engineering study, data representing the existing conditions will be required. This will form the baseline against which proposed alternatives can be compared, and which can be used for future traffic projections. During the planning stages of the project, data should have been collected with the focus on link volumes and distribution of traffic volumes during the day. This data would typically include classified hourly counts of both vehicle (classified by vehicle type) and customer volumes (occupancies in vehicles). Also from the planning stages of the project, data such as Origin-Destination patterns (OD Patterns), vehicle occupancies, existing public transit ridership, and an assessment of possible modal shifts should be available. This information should be sourced for input and evaluation in the Traffic Impact Assessment. Depending on the detail required for the TIA and the extent of the TIA, it could be necessary to collect the following additional information:

  • Classified vehicle turning movement counts at all the major intersections;

    • These counts must be categorized in fifteen-minute intervals and done for at least two hours (preferably three hours) during each typical peak period of a typical day;
    • Where significant issues are expected during shopping peaks on Saturdays or Sundays, these peak periods should also be counted;
    • The counts must be classified by type, i.e., cars, buses, minibuses, paratransit, trucks, pedestrians, and bicycles;
  • Turning-movement counts at the major accesses along the corridor with similar requirements for the counts as outlined above;
  • Link-volume counts (between major intersections) classified by vehicle type on all the major routes in the proposed BRT corridors and also along important parallel routes. These counts should preferably be done for a full day in order to define the variation in traffic demand over a typical day, not only in terms of the total traffic volume, but also the variation in demand for each of the different modes;

  • If not available from the local agencies or from the planning studies for the BRT, the following information must also be collected (see Chapter 4);

    • Vehicle occupancies;
    • Modal shift;
    • Public transit ridership;
    • OD patterns.