In the past several years we have done a number of transportation analyses supporting apartment developments intended for student housing. As noted by Mr. Hogue, the ITE Trip Generation Manual contains data for a number of independent variables, but to the issue raised by Mr. Bennett, it does not well-address trip generation for apartment units with a number bedrooms, each occupied by a student or students.
To address this issue, we have collected field data for similar uses and used this information to determine trip generation - typically using bedrooms as the independent variable. For most, if not all of these projects, trip generation and traffic impacts have been a significant political issue and field data collection seems to be the best solution - although it doesn't eliminate controversy. One of the things we have found is that for students, the person trip generation rates are typically higher than would be calculated using ITE; however, the mode split is significantly different - i.e, on a person trip basis, more than 50% of the trips are made by modes other than an automobile.
Overall, because of the uniqueness of your issue, and the fact the mode split for students is different than for ITE Trip Generation Manual data, I suggest requiring applicant's transportation analyses sfor these apartment uses be based on field-collected trip generation data for similar uses.
Christopher M. Clemow
Transportation Engineer
Mackenzie
Portland, Oregon
cclemow@mcknze.com