The London Congestion Charging Scheme was meant to reduce traffic in central London with the hope that it would also boost air quality – however, a new study published by the Health Effects Institute (HEI) suggests it is failing to meet the latter objective.
Admittedly the scheme was designed to improve traffic rather than air quality – but early projections suggested it would have this effect too. However, according to Professor Frank Kelly and his team at King’s College London, the projected declines have not come to fruition.
The investigators did not find consistent evidence of improved air quality and said that it is in part difficult to assess improvements from a specific programme, especially one targeted area within a large city.
Within the zone, the investigators projected a net decline of 1.7ppb in the annual average mean nitrogen oxide concentration, and a decline of 0.8ug/m3 in PM10. It also suggested a major proportion of PM10 might be accounted for by regional background levels.
Dan Greenbaum, the president of the HEI, believes that air pollution does not know precise boundaries so any benefit appears to have been lost in the larger regional mix.
In addition, some behavioural adjustments among the population may have offset any benefits. These include increased diesel powered taxi and bus trips to transport people into the zone.
It is hoped that the results of the study will help other administrations considering traffic management schemes to achieve vehicle reductions, as well as improving air quality.
