UK commuters spend an average of about 1.5 hours a day at the wheel. Researchers at the University of Surrey have now found that where drivers spend just 2% of the journey time at traffic intersections managed by lights, this short duration contributes to about 25% of total exposure to nanoparticle emissions. Their study is published in the journal Atmospheric Environment.
PNCs [particle number concentrations] and change in driving speed showed an exponential–fit relationship during the delay events at TIs [traffic intersections]. Short–term exposure for ∼2% of total commuting time in car corresponded to ∼25% of total respiratory doses.—Goel and Kumar
The team monitored drivers’ exposure to particle number concentrations (PNCs) at various points of a journey. Traffic intersections with signals were found to be high pollution hot-spots due to the frequent changes in driving conditions. With drivers decelerating and stopping at lights, then revving up to move quickly when lights go green, peak particle concentration was found to be 29 times higher than that during free flowing traffic conditions.
As well as concentration, researchers found that as cars tend to be close together at lights, the likelihood of exposure to vehicle emissions is also significantly increased.
Our time spent travelling in cars has increased by over 10% in the last ten years and with more cars than ever joining the roads, we are being exposed to increasing levels of air pollution as we undertake our daily commutes.
It’s not always possible to change your route to avoid these intersections, but drivers should be aware of the increased risks at busy lights. The best ways to limit your exposure is to keep vehicle windows shut, fans off and try to increase the distance between you and the car in front where possible. Pedestrians regularly crossing such routes should consider whether there might be other paths less dependent on traffic light crossings. Local transport agencies could also help by synchronizing traffic signals to reduce waiting time and consider alternative traffic management systems such as flyovers.—lead author, Dr. Prashant Kumar
Anju Goel, Prashant Kumar (2015) “Characterisation of nanoparticle emissions and exposure at traffic intersections through fast–response mobile and sequential measurements” Atmospheric Environment doi: 10.1016/j.atmosenv.2015.02.002