The following utility function was calibrated based on an observed mode split of 84.9% private auto use and 15.1% bus use. Utility function: Uk = Ak – 0.10 X1 – 0.13 X2 – 0.12 X3 – 0.0045 X4 After implementing service improvements to the buses, the mode split changed to 81.6% private auto use and 18.4% bus use. Determine a value for the calibration constant for the bus mode that reflects this shift in mode split.

Question

A mode choice logit model is to be developed based on the following information. A

survey of travelers in an area with bus service found the following data:





What will be an ideal response?

Answer 1

Using the given information prior to the bus service improvements, the utility

functions are:

Uauto = – 0.33 – 0.10 (0) – 0.13 (20) – 0.12 (5) – 0.0045 (225) = –4.54

Ubus = – 0.27 – 0.10 (10) – 0.13 (35) – 0.12 (0) – 0.0045 (100) = –6.27

Using the new mode split data, the calibration constant for the bus utility function

will need to be recalculated. The logit function for bus service that reflects this

shift can be written as:



Ubus = –6.03

The bus utility function and new value for Abus can now be solved.

Ubus = Abus – 0.10 (10) – 0.13 (35) – 0.12 (0) – 0.0045 (100) = -6.03

Abus = – 0.03