The congestion charge is an economic disincentive (fee) to the use of congested roads at the busiest times of the day. A congestion charge is different from road pricing (road tolls), although they may be perceived by some highway users in the same way. Road pricing is typically implemented as a way of paying back the cost of a debt-financed road – meaning that the road pricing toll is paid whether the road is congested or not. In comparison, congestion charges are targeted at providing economic disincentives for the use of congested roads at congested times.
To be successful, the congestion charge must be accompanied by complementary services that provide a valid alternative to the car even if this can make it difficult to differentiate the environmental benefits attributable to each measure.
Experiences from frontrunner cities show that congestion charges can be an effective means for achieving multiple policy objectives such as:
- reducing traffic volumes in a specified area
- increasing the efficiency of the transport system as a whole
- encouraging people to use public transport, walk and cycle
- raising finance for a city.
From an environmental perspective, this entails reductions in air and noise pollution, as well as opportunities to improve the quality and attractiveness of the city centre.
To maintain over time the significant and immediate effects on traffic levels generated by the congestion charge, cities should identify supplementary measures that reinforce the attractiveness of alternative transport modes, and implement them gradually as congestion levels are reduced to deter citizens from finding driving to the city centre attractive again. Cities where a high percentage of car parking is provided by private companies rather than the public authority must also consider the possibility that the effect of implementing a congestion charge could be diminished if private organisations decide to reduce parking fees inside the charging zone.