Do external benefits compensate for external costs of transport?

Positive externalities of transport play a growing role in the political discussion. If one concentrates on externalities of infrastructure use it is easy to show that the number and the relevance of positive externalities is low. Most of the effects mentioned such as improvement of economic efficiency or development of new consumption/production structures are basically not external but normal consumer’s or producer’s surpluses induced by market interactions. Therefore, there is no reason to subtract external benefits from the external cost bills of traffic modes which are detrimental to the environment.