March 19


Review of Trip Generation Handbook, 3rd Edition

By Mike Spack

March 19, 2015

Forecasting, Traffic Engineering, Traffic Impact Studies, Trip Generation

Guest Post from Bryant Ficek, PE, PTOE – Vice-President of Spack Consulting

Trip Generation Handbook 3rd EditionIt’s long and academic, but I finally managed to read through the 3rd Edition of ITE’s Trip Generation Handbook. Published just last year in August, this updated manual provides guidance on the use of and how to collect trip generation information.

As the Handbook itself states, the objectives are to:

  • Provide guidance on proper techniques for estimating trip generation
  • Encourage standardization of trip generation data collection efforts
  • Support and facilitate analyst ethics and objectivity in its use

Most of the document is similar to the previous edition in terms of how you should use the trip generation material. The big change for this edition is a transition to estimating person trips. The strict definition of a person trip is “a trip made by any mode of travel by an individual person from an origin to a destination.” This means that a family of four leaving their house in one car counts as four person trips.

By calculating person trips, we can then divide the person trips into the various modes of travel (car, transit, bike, walking, etc.). Although a hotel is assumed to have the same average amount of person trips, the amount of traffic will vary considerably between a downtown hotel and a rural hotel. This process should allow us to provide more accurate and tailored estimates of development impacts on the transportation network.

While the Handbook provides the formulas to use and some base data, we need lots more data to start forecasting person trips. Using the Handbook recommended methods for collecting this data means observations and interviews, which unfortunately is a very labor intensive process.

To get person trips, a combination of video/tube counts and interview data needs to be collected. This is because you may not be able to see the person exit a bus a block away and then walk to the site. The person trip should be considered transit in that case, but you may only know that if interview the person when they arrive or leave the site.

My basic opinion, this transition will be a good thing and will provide us more data for more accurate studies. However, it will take time and effort (cost) for us to get there.

Mike’s take:  Like Bryant, I think moving to person trips is theoretically great for the industry.  I posted on the ITE Community wondering if anyone had collected this type of data and how they did it – I got one response (they did it the very laborious way of doing interviews in Australia).  I like collecting data to help the industry, but collecting person trips is too labor intensive for us to do on a volunteer basis at Data Inc.  Since ITE came up with this new methodology (and they make a lot of money selling the data), I hope they will invest in collecting this new person trip data.

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Mike Spack

My mission is to help traffic engineers, transportation planners, and other transportation professionals improve our world.

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