The government has been told to revisit its Air Quality Plan because the measures proposed to address exceedances of NOx in many urban areas do not go far enough or fast enough. Under the Air Quality Directive 2008 and the implementing UK regulations, the government is obliged to take steps to ensure compliance with NOx limits "as soon as possible". The government's plans to do so were challenged by NGO ClientEarth for being inadequate.

The judgment in ClientEarth (No.2) v SSEFRA, handed down on 2 November, was the second time in 18 months that a UK court has agreed with the NGO. On 29 April 2015 the Supreme Court ordered that the government revisit its plans in relation to the Air Quality Directive. The latest ruling has held that the government’s revised plan – drawn up in light of that earlier judgment – is also inadequate. The Prime Minister has told parliament that the government does not intend to appeal this judgment and that it will enter into discussions with ClientEarth on timeframes for revising the plans.

Whatever the outcome of discussions, the likelihood is tighter controls on emissions in a shorter period and over a greater geographical range than the government's plans to date. Diesel vehicle combustion engines are a key culprit and construction traffic may find itself subject to charging schemes in numerous urban areas. Control over other emission sources, such as on-site diesel generators, might also be scrutinised. The lead-in time for implementation once plans are announced will be short and so businesses will not be given much time to react. Those involved in construction projects should consider now the possible range of practical measures they could take and make appropriate provisions in their commercial arrangements.