Resource efficiency for UK cars from 1960 to 2015: From stocks and flows to service provision

The transport sector is supported by the continuous provision of energy and material flows and material stocks. However, most resource accounting methods do not assess the role of material accumulation in the delivery of mobility, as a service. Using a UK-based case study, we evaluate the service contribution of both resource stocks and flows in the provision of the passenger-kilometres (pkm) travelled nationally by UK-registered cars between 1960 and 2015. For flows we considered diesel and petrol. For stocks we considered steel, aluminium, and plastics, among others. We used six indicators to analyse the interactions between stocks, flows and service. Our results show that the fuel efficiency of cars increased from 0.46 to 0.69 pkm/MJ over the period. However, there was a decrease in stock efficiency from 24.9 to 17.1 pkm/kg-year. Resource productivity increased from 0.42 to 0.61 pkm/MJ. Stock expansion rate decreased from 0.16 to 0.03 year−1 while the specific CO2 embodied impact reduced from 2.4 to 2.0 tCO2/tonne of resource flow. Consumer preferences for heavier larger vehicles and sociodemographic changes linked to workplace expectations, commuting and urbanisation patterns are key factors influencing UK car stock efficiency. While fuel efficiency has improved and will continue to do so via the mass adoption of electric vehicles, due to policy and legislative developments, there are still sustainability concerns linked to their heavier weight and the environmental impact of their increased material complexity.