Climate change: evidence review of mitigation options in the Transport sector

Executive summary

• This evidence review is based on a systematic literature review of over 100 papers on the wider impacts of climate change mitigation in the transport sector. The review looked at qualitative and quantitative sources of relevance to the Scottish context. Particular consideration was given to the impacts from an equalities perspective.
• Overall the evidence base suggests there are a number of potential co-benefits associated with transport climate change mitigation measures. Health benefits associated with increased levels of walking and cycling dominates the literature. Reductions in car vehicle kilometres whether through modal shift or demand reduction ( e.g. through teleworking) can offer air quality improvements, noise and congestion reduction. There is also an emerging evidence base on the co-benefits of improved transport efficiencies. However, the extent of these benefits, particularly from an equalities perspective, is dependent on how and where policies are implemented and the extent of consumer uptake and acceptance.
• Transport is a major contributor to air quality pollutant emissions. An emerging literature base suggests that improvements in vehicle efficiency for example, through the use of electric vehicles can offer benefits here. Further understanding relating to population exposure and the spatial distribution of these vehicles to ensure these benefits is required. The evidence base suggests links between socially deprived neighbourhoods and exposure to higher levels of air pollution, thus consideration should be given to the geographic positioning of demonstration schemes and grants to help facilitate equitable, social and distributional benefits of these vehicles.
• There are opportunities too with regard to the potential for noise reduction through the use of electric vehicles, however a fuller understanding of the implications of the European Commission's required introduction of sound generating devices (for safety purposes) on these vehicles is necessary to better understand the extent of this potential reduction.
• Modal shift from car to public transport and walk and cycle can potentially bring about reductions in noise, air pollution and congestion. The level of benefit depends on the extent of modal shift in terms of car vehicle kilometres reduced, and where and when these reductions take place. For public transport modes, the impacts will be greatest when the modal shift is to cleaner vehicles. To capture these potential benefits, guidance is available at the UK and Scottish level. In terms of quantitative approaches, recent Defra modelling work may be highly relevant. Identification of opportunities from an equalities perspective is required e.g. the location of bike share schemes in areas where the numbers of existing cyclists is limited.
• There is strong evidence that active travel interventions can, through increased physical activity, bring about substantial health benefits. These health benefits relate to reductions in disease and mortality. Quantitative tools and models exist to capture these benefits. To quantify the benefits of reductions in disease in the Scottish context, further work is required. Scottish based research is making important contributions to the real life evidence base with regard to the increased adoption of active travel measures. In terms of ensuring equitable distribution of benefits, further understanding is required to help ensure those that are currently less likely to walk and cycle are reached. This could include innovative methods such as electric bicycles.
• Action may be required to lock in these benefits, for example through demand management. Demand management offers opportunities in terms of congestion reduction and can be used as an incentive to facilitate the adoption of lower emission vehicles. There are close links with land use planning and the facilitation of modal shift.