The Institute of Transportation Engineers’ (ITE) Trip Generation Manual suggests that “the user may wish to modify trip generation rates presented in this document to reflect … special characteristics of the site or surrounding area.” We translate this suggestion as a directive to obtain local data when possible because it will be more accurate than a national average. And now we have further proof of that.
Our friends from the Florida Department of Transportation, Gary Sokolow, Nathan Hicks, and Michael Stafford, provided us a wealth of new trip generation based on their work. (Thank you gentlemen!) Combined with our trip generation information, we can begin to see how these local characteristics can result in significant differences between rates. The trip generation rates for a gas station and student housing are shown in the tables below.
You can review the full data and more at www.TripGeneration.org. That’s our free site to share trip generation data with everyone, with currently over 5,000 hours of professionally collected traffic data for popular land uses.
When comparing rates for the gas station, ITE underestimates both Florida and Minnesota data. The Florida rates are closer, particularly the peak hour rates. Since most traffic impact studies examine the peak hours, the difference is probably within the margin of error and not likely to change the final recommendations. Minnesota is at least 24 percent higher across the board. Imagine missing one out of every four cars in your study and you can easily see how major impacts could be missed.
Why are Minnesota rates higher? It’s likely a combination of local factors, such as cold winters that keep many people from walking or bicycling more than a few blocks and suburban areas with few transit options that force people to use their cars more often.
Turning to Student Housing, we can clearly see Minnesota rates are significantly lower while Florida rates are significantly higher. Local factors are again at work. In Minnesota, parking is scarce and expensive. With many housing options on campus or very near campus, the short walk to class does not require a car. In Florida, multiple parking garages are available and parking is viewed as “free” since the transportation fee is combined with tuition. A lack of pedestrian/bicycle/transit infrastructure could also be a cause here.
Whatever the exact reason, the differences between the Florida, Minnesota, and ITE trip generation rates are clear. With often expensive infrastructure decisions depending upon our analyses, local trip generation is obviously the best way to account for each area’s diverse set of circumstances.
Want to partner with us to collect your own local trip generation data? We have a limited pool of COUNTcam video collection products that we’re lending for free specifically for this purpose. Contact Sales at CountingCars.com or leave your contact information in the comments section if you’re interested.