BAQMG begin work on the Updating & Screening Assessment  Local authorities have already carried out their first round of reviews and assessments to determine the need for designation of any AQMAs in their area. This first round should act as a benchmark against which local authorities can measure their future progress in making improvements to their local air quality. Over 100 local authorities across the UK have to date designated AQMAs in their areas. The vast majority of these AQMAs are in respect of emissions from road transport with only a small percentage being designated in respect of industrial sources alone. Other AQMAs have been designated as a result of other transport-related emissions such as in the vicinity of airports or due to emissions from shipping. The vast majority of AQMAs have been designated in urban metropolitan boroughs but several are located in smaller market towns due to the street canyon effect, where the roads are narrow, traffic congestion is a problem and air pollution is unable to disperse effectively. An evaluation report published in March 2002 set out the main thoughts and suggestions on the first round of air quality reviews and assessments. One of the key recommendations suggested that the next round should be carried out in two steps: Updating and Screening Assessment for identifying those aspects that have changed since the first round of reviews and assessments, including by way of lessons learnt from the first round, that may require further assessment. and Detailed Assessment of those pollutants and specific locations that have been identified as requiring further work - i.e. where members of the public are likely to be exposed over the averaging period of the air quality objective.