Unexpected Results in Logit Model with Repeated Choices in Biogeme

[朱铭锴]

Dear all:

I’m currently building a logit model in Biogeme. In my setup, each respondent makes a choice among three main alternatives — POD A, B, and C — under nine different scenarios. So in total, each individual makes nine choices.

Each alternative (POD A, B, and C) has three key attributes:

• Wait time (15 min, 45 min, 60 min)

• Travel time (<1 hr, 1–2 hrs, >2 hrs)

• Parking (limited, moderate, extensive)

In each of the nine scenarios, the attribute values for each alternative are different. I am currently modeling only the main effects, without any interaction terms.

To avoid multicollinearity:

• I set the alternative-specific constant (ASC) for POD C to 0 (as the base alternative).

• For each attribute, I excluded one level (i.e., one wait time, one travel time, and one parking level).

My goal is to estimate the respondents’ preference for each attribute level, but the estimation results I get are very different from what I expected.

I’ve included the code and data below. Could someone help me understand what might be going wrong?

I have attached the data and code to this email

Thank you!