Playing the Numbers Game

Traffic study methodologies draw data from and are designed to analyze single-use, auto-oriented suburban developments. This creates a serious challenge for transit-oriented developments (TODs). For TOD's, the use of unadjusted average Institute of Transportation Engineers (ITE) trip-generation rates often will drastically overestimate the amount of traffic generated. This in turn leads to a tendency to overbuild the transportation infrastructure in terms of parking and traffic lanes. Many of the tools needed to change this situation are already available, and the ITE has long recommended that traffic engineers take into account alternatives to the private automobile and modify trip-generation rates accordingly. However, many engineers and municipalities still lack the knowledge and willingness to use alternative trip-generation methodologies. One way to deal with the inherent uncertainty of traffic analysis is to place less emphasis on traffic forecasts and to focus instead on achieving a specific trip reduction as a policy goal. Planners should also push for more funding to expand the ITE trip-generation database, and encourage further research on the links between neighborhood design and travel behavior.