A discrete choice model is presented that explicitly recognizes differ
ences in the error structure associated with a single ''oddball'' alte
rnative within the choice set that has properties not common to the ot
her alternatives. The model purportedly resolves questions related to
the use of alternative-specific variables in transportation choice mod
els to capture the effects of attributes unique to a single travel alt
ernative, such as ''schedule frequency'' in the case of modal choice b
etween personal auto and public transit. The model, which shares the g
eneral error structure of multinomial legit, is shown to be a modifica
tion of a multinomial legit subchoice by terms involving the exponenti
al integral. The model is shown to yield different results from those
produced by an equivalent multinomial legit specification. Comparisons
to multinomial probit and nested legit formulations are also made.