Optimal road-pricing: Simultaneous treatment of time losses, increased fuel consumption, and emissions

In this paper, optimal road-charges are derived with respect to congestion, emissions, and the corresponding excessive fuel consumption and emissions due to the congestion. It is shown that a road-user should then pay a charge corresponding not only to its own emissions, but also to the increased emission and fuel consumption of other road-users. It is demonstrated in a numerical example that these ‘system effects’ may be significant. Furthermore, a new flexible speed–flow relationship is introduced which incorporates the linear speed–flow relationship as well as the linear speed–density relationship (for different parameter values). The optimal pure congestion charge is then expressed solely by the equivalent congestion factor, the average value of time, the actual speed, and the speed at which the maximum flow occurs.