In urban transit network design it is commonly presumed that all travellers walk to the halt they need. This might hold true for short-access distances but as soon as the halt and line spacing increases other transport modes, such as bikes, might become interesting as alternative access modes. In this article an analytical model is presented for determining optimal network characteristics, that is: stop spacing, line spacing and frequency. It is a model which also explicitly accounts for alternative access modes. The whole stated objective is that of maximising social welfare. Results show that if cycling is to be seen as an alternative access mode then all three characteristics of urban transit networks should be increased, thus providing benefits for the traveller, the operator and society as a whole. However, if there is a large sub-population of travellers unable to avail themselves of the alternative mode or if there are barriers to using alternative modes to gain access to the transit system then one must assume that walking is the only access mode available. If cycling becomes the alternative accessing mode then there are definite benefits to be gained from this. It is predicted that with other possible access modes, such as people movers and demand-response transit systems, the thresholds will be too high to have any impact on urban transit network design. (Author/publisher)
Abstract