It is well known that cars are a main cause of atmospheric pollution. However, the emissions coming from your tailpipe aren’t always the biggest contributor. When the weather situation favors the creation of winter smog, tailpipe emissions account for less than half of the fine particulate pollution from your car. The majority of this pollutant is produced by mechanical wear and resuspension of dust due to air turbulence from passing vehicles.
The fine particle matter released by combustion processes, and mechanical wear, and that thrown up again swirling air can no longer move into the higher layers of the atmosphere, with the result that the concentration at ground level increases. Working together with the Road Engineering / Sealing Components Laboratory, the atmospheric specialists developed a new measuring method using Empa's Traffic Load Simulator. This machine is normally used to investigate the time-accelerated resistance to wear of road surfaces under extreme load conditions.
The results of the study showed that in urban area debris from vehicle brakes contributes about 20% of the fine particle emissions from road traffic because of the regular nature of traffic flow. Damaged roads surfaces, on the other hand, can result in quite high fine particle emission levels. What this means is that keeping roads as clean as possible and in good repair makes a significant contribution to reducing the problem of fine particulate emissions.
Empa. "Clean streets and intact road surfaces help to keep the air clean." ScienceDaily 1 February 2011. 1 February 2011