It is well recognized that new road investment produces induced traffic, so it is necessary to consider the induced traffic in the appraisal of road investments. Benefit estimated by the fixed origin-destination (OD) matrix method will be biased, although the method has been used traditionally. An easier treatment of induced traffic is elastic OD matrix model, but it is difficult to assume reliable parameters of elasticity in the model and the result varies largely according to the parameter. In view of drivers' behavioural side, induced traffic is explained mainly by change of route, change of mode, change of travel destination, and increase of trip frequency when a new road is open. The 4-Level Nested Logit model, that is travel choice, mode choice, destination choice and route choice model was used to express these behavioural responses. The level of services in nested logit model varies according to network congestion, so equilibrium conditions were considered. A Logit type Stochastic User Equilibrium model was used. The mathematical optimization problem that is equivalent to the whole of 4-level NL model and SUE model was formulated. Consistent results are given by solving this optimization problem. There are no internally inconsistent problems in the demand model such as in the conventional 4-step travel demand model. The model includes formulated models for each traveller's trip purposes in travel choice, mode choice and destination choice phase. The combined model was applied to the Tokyo Metropolitan Area. Parameters in the nested logit model are estimated for each trip purpose and each time period with Person Trip survey in this area. A multi-mode and large scaled transport network data using GIS platform was used. The road network has more than 22,000 links and railway network has more than 4900 links. The network congestion is expressed by conventional link performance functions in road links and discomfort functions in railway link. The discomfort functions explain the travellers' discomfort in the crowded train, which is needed to express the railway highly congestion in peak period in Tokyo area. The user benefit of Tokyo Outer Ring Road (Tokyo Gaikan Expressway), which is actually planned in Tokyo Area, was estimated with this model. Some people change their travel mode from railway to automobile because of increased accessibility of the road system according to our model. This modal shift would worsen the congestion in road network, but partly relieve the congestion in the railway network especially in the peak periods. So the induced traffic caused by the modal split partly raises total social welfare in this case. The increased accessibility brings another induced traffic that consists of longer distance trips by changing destination and increased trip frequency. The benefits estimated by the combined model considering induced traffic are compared with the fixed demand model. The benefits by the conventional fixed demand model are overestimated. For the covering abstract see ITRD E124693.
Samenvatting