INTERNALISING THE SOCIAL COSTS OF TRANSPORT

ing from distributional problems for the moment, there is little reason for treating this club good like a public good and for producing or allocating transport services according to public rules. On the other hand, the transport infrastructure is characterised by a sub-additivy of costs, and its use leads to external diseconomies. Therefore, a high level of public control is needed to prevent the transport market from natural monopoly and from distortions by externalities. The conclusion is that public control is necessary, but that economic market instruments directed at the private sector are often feasible.