The demand model captures the essential features of a transport CBA but is as homogeneous as possible: it considers only one class of travelers and one ticket price. For simplicity ,the fare pi is assumed to be constant and exogenous.4 The generalized travel cost is defined as ci¼piþαtiþβS/ni, where S/ni is the average waiting time, and α and β are monetary values of travel time and waiting time.5 Travel demand between the stations is Di¼Di(ci). In the numerical examples we will assume a demand function with constant elasticity ε such that DðcÞ ¼ D0ðc=c0Þε. The consumer surplus (CS)of a change in generalized costs from{ci0} to{ci1} is by definition