A computer-implemented method of constructing a transit transfer network from transit data comprises processing transit data to define a plurality of transfer endpoints; determining a set of acceptable transfer durations for each of a plurality of transfers associated with the transfer endpoints; determining one or more groups of endpoints to be merged, each group comprising two or more endpoints, wherein transfers associated with the endpoints in each said group have one or more common acceptable transfer durations; and merging the endpoints in each group to form one or more merged endpoints.