Efficiency and equity of ramp control and capacity allocation mechanisms in a freeway corridor

This paper investigates the efficiency and equity of morning peak ramp control schemes in a freeway corridor with limited capacity. In terms of efficiency, both short-run and long-run optimal ramp control schemes are obtained by minimizing the total travel cost and maximizing the total social benefit along the corridor. It is found that for a short-run optimum with inelastic demand, the morning peak period is of the same duration for different on-ramp locations. But for a long-run optimum with elastic demand, the peak duration for various on-ramps increases with the local capacity elasticity of demand. In terms of equity, two measures are defined from a demand-based viewpoint and a space-based viewpoint. It is shown that the short-run optimal ramp control scheme is perfectly fair from a demand-based equity viewpoint. Consequently, two typical ramp control schemes-a perfect demand-based equity scheme and a perfect space-based equity scheme-are introduced and compared with the long-run optimal ramp control scheme in terms of efficiency and equity. It is shown that the long-run optimal ramp control scheme without an equity constraint is more unfair than the perfect demand-based equity scheme from a space-based equity viewpoint. Numerical simulations using survey data from China suggest that the perfect demand-based equity scheme attains an economic welfare level that is very close to the optimal one.