Why Change Behaviors ? Cost-Benefit Analysis Of Different Strategic Scenarios With Respect To Sustainability And Equity

Why Change Behaviors ? Cost-Benefit Analysis Of Different Strategic Scenarios With Respect To Sustainability And Equity


Richard GRIMAL, Center for Expertise and Studies on Risks, Environment, Mobility and Town Planning (CEREMA)


In this study, a cost-benefit analysis of different strategic scenarios in terms of equity and sustainability is carried out by forecasting levels of car traffic, GHG emissions and fuel budget coefficients in 2060 through an ad hoc model.


With continuous growth in household car ownership and the resulting traffic, externalities related to car use have also increased, either in terms of congestion, pollution, or climate change. In order to mitigate climate change, French decision makers have implemented various policies focused in reducing car use. At the national level, laws have been designed, like the law of energetic transition settling a “carbon tax” on GHG emissions as a component of the national tax on oil products. At the local level, significant efforts have been made in improving transit supply, settling free-duty bike sharing systems, reducing authorized speed limits, creating dedicated lanes or reducing parking space, resulting in reduced facilities for car traffic within inner cities and downgrading the relative efficiency of the car. However, these policies might have attained their limits, given saturated transit systems with increasing malfunctions resulting in a degraded quality of life for city dwellers, and their helplessness in dealing with car dependency in low-density residential areas, in a context of rising fuel prices over the two last decades. Moreover, climate mitigation goals are seldom put into perspective with equity issues in order to design optimal sustainable travel policies, achieving GHG cuts without generating excessive social costs. In order to introduce a discussion about potential costs and benefits of various strategic scenarios with respect to both equity and sustainability issues, an ad hoc model is designed to estimate future levels of car traffic, GHG emissions and the ratio of travel expenditures to income in 2060, in relation with demographic forecasts by sex and age group from the model OMPHALE of the French National Institute of Statistics and Economic Studies (INSEE). Traffic generation is calculated from a sequential model, segmented by gender, and disaggregated at the individual level, from driving license to personal car availability and car mileages. It is estimated with the panel dataset from the French Car Fleet Surveys. The consequences of different scenarios are considered, according to different assumptions about income growth, fuel prices and vehicle efficiency. These scenarios are called “business-as-usual” as travel behaviors of generations to come are assumed to be identical to the last generations with well-known travel behaviors, described on their full lifecycle. Modeling results tend to prove that the main benefits in terms of GHG cuts are to be expected from increasing average vehicle efficiency of the vehicle fleet. In addition, a scenario of technological progress associated with moderate fuel prices is also beneficial for households in terms of mobility and budget coefficients. By contrast, the environmental benefit of highly increasing fuel prices is moderate as the travel reduction it brings is limited by car dependency, while generating high social costs. We finally discuss some implications of these results for travel policies. Policy sets based on research and innovation funding and the diffusion of technological progress through financial incentives to accelerate the renewal of the vehicle fleet appear as the best way to answer to both equity and sustainability issues by leading to GHG cuts without excessive social costs. In turn, modeling results highlight the need for compensatory measures to mitigate the potentially negative social outcomes of increasing levels of taxation, especially with the implementation of the carbon tax. Policies based on the price signal may also have limited environmental benefits, given car dependency which is resulting in a low price elasticity of car travel.


Association for European Transport