ABSTRACT
This chapter draws on two manuals published by the Institute of Transportation Engineers (ITE)—Parking Generation and Trip Generation. Urban planners rely on parking generation rates to establish off-street parking requirements, and transportation planners rely on trip generation rates to predict the traffic effects of proposed developments. Few planning decisions would be changed if ITE reported the trip generation rate as 632 rather than 632.125 trips per 1,000 square feet, so the three-decimal-point precision serves no purpose except to falsely suggest that the estimate is accurate. Placing unwarranted trust in the accuracy of precise but highly uncertain data leads to bad policy choices. We need less precision and more truth in transportation planning. The breathtaking combination of extreme precision and statistical insignificance in parking and trip generation rates at fast-food restaurants raises an important question: How many of the rates for other land uses are statistically insignificant?.
