Urban and national road networks in many countries are severely congested, resulting in increased travel times, unexpected delays, greater travel costs, worsening air pollution and noise levels, and a greater number of traffic accidents. Expanding traffic network capacities by building more roads is both extremely costly and harmful to the environment. By far the best way to accommodate growing travel demand is to make more efficient use of existing networks.
Portugal has a good but underused toll highway network that runs near to an urban/national road network that is free to use but congested. In choosing not to pay a toll, many Portuguese drivers are apparently accepting greater risk to their safety and longer travel times. As a result, the urban/national road network is used far more intensively than projections anticipated, which raises maintenance costs while increasing levels of risk and inconvenience. The main idea behind this pilot study is to motivate a shift of traffic from the overused network to the underused network. To this end, a model for calculating variable toll fees needs to be developed.
Dynamic pricing can reduce congestion by shifting some traffic to alternative times, routes or modes — or by eliminating trips. Previous studies have shown that when transportation agencies implement variable pricing, drivers significantly shift their travel patterns around the pricing structures. Drivers reduce peak-period travels and take greater advantage of discounted, off-peak periods. The adoption of new, variably priced express lanes allows traffic to flow at higher speeds and volumes than general purpose lanes, thus reducing congestion. They also boost overall vehicle throughput.