Traffic management during high pollution episodes: a review

This report attempts to identify those conditions that give rise to high pollution episodes and, through a review of existing research and pilot studies, evaluates the potential of traffic management to reduce both the frequency and magnitude of these episodes. Although the number of high pollution episodes in the UK has declined, such episodes continue to occur. Fewer episodes are now associated with primary pollutants, such as carbon monoxide. Increasingly those episodes that do occur are now more likely to be associated with elevated concentrations of secondary pollutants such as nitrogen dioxide, particulates and ozone. There is a potential to influence the magnitude or occurrence of a high pollution episode by reducing emissions from the transport sector, through the use of a range of traffic management initiatives. To enable the modification of routine travel patterns, it is essential that advanced warning be given for an event. Reliable forecasts are thus required to provide an appropriate advanced warning and response system. The existing status of pollution modelling appears to be insufficient to ensure an accurate forecast for periods in excess of 2 days. However, with the use of a staggered forecast and response system, current developments in modelling techniques are likely to be sufficient, albeit with a possible incorrect quantitative assessment. (A)