Road safety experts understand the contribution of speed to the severity and frequency of road crashes. Yet, the impact of speed on health is far more subtle and pervasive than simply its effect on road safety. The emphasis in urban areas on increasing the speed and volume of car traffic contributes to ill-health through its impacts on local air pollution, greenhouse gas production, inactivity, obesity and social isolation. In addition to these impacts, a heavy reliance on cars as a supposedly ‘fast’ mode of transport consumes more time and money than a reliance on supposedly slower modes of transport (walking, cycling and public transport). Lack of time is a major reason why people do not engage in healthy behaviours. Using the concept of ‘effective speed’, this paper demonstrates that any attempt to ‘save time’ through increasing the speed of motorists is ultimately futile. Paradoxically, if planners wish to provide urban residents with more time for healthy behaviours (such as exercise and preparing healthy food), then, support for the ‘slower’ active modes of transport should be encouraged.