Less Pollution, Better Mobility
Both Stockholm and Gothenburg have implemented congestion charging with substantial effects on traffic flows (-20% and -10%), travel time improvements (-30% and -25%) as well as gas emission reductions (-8% and -5% (NOx)). Congestion charging has thus proven to be very effective in reaching its primary political objectives of reducing congestion and emissions.
Congestion charging also generates a considerable revenue stream that can be used to strengthen sustainable modes of transportation with additional investments. In both Stockholm and Gothenburg, infrastructure investments are made possible by congestion charging revenues which provide about half of the necessary funding.
WSP in Sweden has been the lead consultant for the Swedish Transport Administration in the policy design for both Stockholm and Gothenburg, as well as the evaluation of the policy effects in Stockholm. The work includes developing demand forecasts, cost-benefit analysis, as well as environmental and economic impact assessments for alternative policy schemes. In terms of evaluation, the work included defining suitable KPIs, monitoring plans, measurement and data collections design, and resulting statistical analysis and reporting. It is an ongoing project since 2005 with the latest work being evaluating the effects of system changes in Stockholm effective January 2016.
Building the Case for Congestion Charging
The main challenges in developing sound congestion charging policies lie in translating the often implicit political objectives and constraints into a practical, feasible and understandable scheme for travellers.
The variables for a congestion charging design in terms of where to charge, which vehicles, at what time and how much, are extensive. Simultaneously initial public resistance is often significant, which increases political risk. Therefore, designing congestion charging policies must rely on solid scientific research and trusted transportation modelling that steers the decision making process with quantified estimates of alternative policies.
WSP has put transportation modelling at the heart of an interactive and iterative process with policy makers, which included setting an initial policy objective, analyzing the traffic constraints, as well as assessing, evaluating and refining the economic and environmental impacts. We also developed the monitoring and evaluation plan. Following the congestion charging policy implementation, we assisted with data analysis and public reporting on its impacts.
The scientific and modelling based approach for designing congestion charging helps reduce political risk. It enables investigating numerous alternatives, addressing political objectives and constraints to come up with a design that both politicians and experts can explain to the public as being beneficial to society.