As noted in the introduction to this section, logistic decay functions provide a better fit to the surveyed data than negative exponential functions. Recent work in this area by Abley Transportation Consultants has resulted in the development of a methodology for fitting logistic decay functions to the NZHTS survey data. A significant improvement in the ability to fit the data over the negative exponential function was observed, as similarly noted by other researchers. However, it was not possible to update the entire accessibility model within the timeframe of this research. Work has since been undertaken to include the logistic decay functions into the New Zealand accessibility model methodology.