A major transport project would typically affect the cost of travel of several different alternatives, and give rise to a combination of gains and losses to users of each alternative. The attribution of benefits to each of the travel alternatives needs to recognise that travellers may change their behaviour as a result of the project. These changes in demand arise not only from changes in the cost of each specific alternative but also from cost changes in other competing alternatives. The appropriate treatment of inter-modal effects is central to the determination of the user benefit produced by each alternative. The paper sets out a number of desirable criteria that source-related measures of user benefit should satisfy which include local consistency with the rule of a half. It explores the effect of alternative path specifications on the resulting measures and demonstrate that they can give different results when larger cost changes can occur, such as in modelling a new alternative. Appropriate measures that are able to treat this problem are developed and the results compared to those obtained by numerical methods.
Hyman, G. & Daly, A.J. (2014), The Attribution of Transport User Benefits by Source using Discrete Choice Models. Research in Transport Economics, 47, pp 103-111.