To learn about exposure to traffic pollution, scientists in Boston, Massachusetts, pedalled around their city towing an instrumented trailer. Their results provide useful information for cycle lane design. Perhaps unsurprisingly, least exposure to traffic exhaust was found where cycle paths were separated from roads, especially when lined by hedges and trees. More air pollution was found on bike lanes that run alongside traffic and most pollution was found where cyclists shared bus lanes.

Good cycle paths cost money but the potential pay-back from increasing cycling and walking is huge. A six-mile-a-day car commuter who switches to cycling to work could lead to health savings of around £1,000 per year from increased exercise. Extra benefit also comes from less exhaust emissions. On the downside, cyclists breathe faster and journey time also alters the pollution dose.

The risk of increased accidents from switching to cycling varies from place to place. Driving and cycling are thought to be equally risky in the Netherlands where cycle facilities are good, but cycling is more dangerous than driving in Paris. Despite this, the benefit from cycling is still more than ten times the increased health cost from accidents and pollution exposure. As an alternative to policies that focus on cleaning up vehicle exhausts, a switch to active travel provides many more benefits.

The potential to increase cycling in the UK has been recognised by the Parliamentary Cycling Group. They have called for cycling spending to be increased from the English city-average of £2 to £10 per head to boost cycling from two per cent of journeys to ten per cent by 2020.