On June 1, 2020, Transport Action Network (TAN) filed a suit in the High Court of Justice challenging the legality of the UK government's Second Roads Investment Strategy, covering the years 2020-2025, on climate and air pollution grounds. TAN, an environmental advocacy NGO, named the Secretary of State for Transport as the defendant and Highways England Company, appointed by the Secretary to implement the strategy, as an interested party. TAN listed four grounds for its suit: 1) the Secretary failed to take into account the impact of the roads strategy on achieving climate objectives, in violation of the Infrastructure Act of 2015 and the objectives of the Paris Agreement; 2) the Secretary unlawfully failed to establish a metric for measuring GHG emissions; 3) the Secretary unlawfully failed to ensure levels of air pollutants do not exceed limits set in air quality regulations; and 4) the Secretary unlawfully failed to carry out a Strategic Environmental Assessment of the roads strategy.
On July 21, 2020, the High Court admitted the case on the first ground - that the Secretary unlawfully failed to take into account climate impacts. On October 19, 2020, TAN renewed its application for the court to admit the air pollution claims, and a hearing was held on the issue on October 29, 2020.
On July 26, 2021, the High Court dismissed the case. The Court found that the Secretary of State for Transport, in approving the strategy, had given adequate regard to UK Policy on Climate Change. The Court upheld the Department of Transport's determination that the greenhouse gas emissions associated with the RIS were de minimis and not obviously material to the decision-making process. In the course of the judgment the Court also observed that "there is nothing in the IA 2015 [Infrastructure Act 2015] which remotely resembles environmental decision-making."