Policy measures to reduce road congestion: What worked?

Abstract

Background

Road congestion is a persistent problem. Increasing road capacity has not solved this problem, which requires measures to curb road use demand. This paper reviews recent evidence on the effectiveness of different types of policy measures in reducing congestion through reducing road use. The paper answers three questions: 1) what explains the success or failure of measures in reducing congestion?, 2) is the reduction of congestion sustained in the long term?, and 3) are combinations of measures more effective than single measures?.

Methods

We searched the literature for studies assessing the effects of policy measures that aimed at reducing congestion through reducing road use demand.

Results

Restrictions to vehicle ownership tend to reduce congestion, but road use charging and vehicle restrictions are not always effective as road users circumvent the charges or restrictions. Soft measures such as incentives and the provision of information have mostly short-term effects. More evidence is needed on measures affecting fuel prices, high-occupancy vehicle lanes, and parking policies. Measures to reduce road use demand are more effective when combined with measures to improve public transport.

Conclusions

Policies to reduce congestion in the long term need to account for possible adaptations in road user behaviour and provide alternatives to road travel.