Multi-objective optimal speed for expressways

摘要

Relationships for speed-flow, speed-fuel consumption (speed-carbon emission rates) and speed-accident occurrences for highway (expressway) driving conditions are reviewed. The optimal speeds for maximising traffic flow capacity on highly utilised expressways in Singapore lies in the range of 45-65 km/h, a speed band that the Land Transport Authority (Singapore) uses in its Electronic Road Pricing (ERP). On the other hand, the optimal speed range lies between 50 and 75 km/h based on efficient fuel consumption. As for carbon emission rates of the vehicular flow, the optimal speed range is 50-60 km/h. In terms of accident occurrences, the general norm is that low travel speeds as well as low speed variability are desirable. Experimental runs have shown that a relatively low speed band is preferred for greater fuel efficiency. Setting operating speeds that straddle the optimum regimes of capacity, safety and environmental sustainability suggests a range of 50-60 km/h.