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16 CHAPTER 3 Estimating Airport Roadway Traffic Volumes This chapter presents methods for estimating existing and included installing ATRs at 25 locations typically cost less than future airport roadway requirements. The data required to $50,000 (or about $1,000 to $2,000 per location) excluding analyze existing roadway traffic volumes and operations are any analyses of the resulting data. described, and two alternative methods for estimating future If the analysis of roadway operations is to focus on one road- roadway traffic volumes are presented. One method, the tra- way segment (e.g., a curbside roadway), it may be necessary to ditional four-step approach commonly used by transporta- record only the traffic volumes on this segment and/or adja- tion planners, incorporates estimates of the roadway traffic cent roadways rather than to conduct a comprehensive survey volumes generated by airline passengers, visitors, employees, of all roadways. Similarly, if peak airport traffic periods are air cargo handlers, and major airport land uses. This method known, it may be possible to record the traffic volumes during requires an extensive database for each of these traffic gener- a 3-hour peak period coinciding with this peak period rather ators. The second method, the growth factor method, yields than conduct day-long, 48-hour, or 7-day surveys. acceptable, but less precise results, while requiring much less input data. However, this simpler method is less sensitive to Selecting Survey Dates changes in future conditions or travel patterns. Ideally, the traffic volume and curbside surveys should be conducted during the peak hours on a typical busy day (ideally Establishing Existing Airport during a peak month). Typically, the peak days occur in the Roadway Traffic Volumes months with the largest volumes of airline traffic. At many air- Analyses of existing conditions and estimates of future con- ports, the busiest days are Mondays and Fridays, but at some ditions should be based on observed vehicular activity. Surveys airports--especially those serving large volumes of non- of traffic volumes, roadway operations, and vehicle character- business passengers--the busiest days may be Sundays. istics are often conducted to support these analyses. Additional information about traffic surveys can be found in the ITE Man- Selecting Survey Hours ual of Traffic Engineering Studies and other references listed in the bibliography provided in Appendix B to this Guide. The peak hours for roadway traffic precede the peak hour for originating airline passenger departures and follow the peak hour for terminating airline passenger arrivals. Peak- Roadway Traffic Volume Survey Methods hour traffic volumes can be determined by counting the num- Roadway traffic volumes can be obtained inexpensively and bers of vehicles on the roadway by type of vehicle (for curbside quickly through surveys compared to a planning and forecast- surveys), recording the number of vehicles on the roadway ing analysis. Surveys of roadway traffic can be conducted by during each 15-minute increment, and then either identify- (1) the public works or traffic engineering department of a ing the four consecutive 15-minute increments with the municipality or county using automatic traffic recorders largest traffic volumes or the busiest 15-minute increment. It (ATRs), (2) consulting firms that specialize in conducting is suggested that surveys of the departures area (passenger such surveys, or (3) interns, students, or volunteers recruited drop-off area) roadways be conducted during the 3 hours to manually record traffic volumes on airport roadways. For prior to and including the 60-minute period with the most example, in 2010 a comprehensive 7-day traffic survey that departing flights, and that surveys of the arrivals area (passen-