Professors Jeff Kenworthy and Peter Newman, of Curtin University, have conducted a global survey and found that road building has a poor track record in reducing congestion. It's akin to putting more holes in a belt to solve an obesity problem.

Kenworthy argues that traffic ought to be viewed as a gas, rather than a liquid. Liquids typically hold their volume, regardless of the space provided. Transport planning theory views traffic as a liquid. Thus, the transport planner's job has been to simply provide the necessary volume of road space to achieve an efficient flow of traffic.

A clearer understanding treats traffic as a gas. A gas is able to expand and contract depending on the space provided. Viewed in this way, the transport planner's role is one in which a conversion to the most space-efficient modes of transport becomes the priority. A good transport planner looks to compress traffic by making space-efficient modes of transport more attractive. The tunnel will reward the most space-inefficient form of transport: the single-occupant motor vehicle.

Urban planning expert Jane Jacobs argues that officials often focus on symptoms and ignore causes. In this instance, the Victorian Government sees the problem as traffic congestion; so, the obvious solution is to widen the road. However, congestion is the symptom. Dependence on motor vehicles is the problem.

Moreover, only about 9% to 12% of traffic exiting the Eastern Freeway actually heads for the western suburbs. Why, then, spend $9 billion facilitating a mobility pattern that people don't actually use?

(Elliot Fishman is director of the Institute for Sensible Transport, which lobbies to reduce car use in urban areas. )