Last month, the government published a fresh consultation on the document that will guide the planning decision on Heathrow's third runway. The latest consultation on the draft aviation NPS, issued by the Department for Transport last week, was required because the government needed to update its expectations of how air quality would be affected by a new runway at Heathrow, following publication of its air quality strategy in the summer.
Also, the government had been restricted from publishing its latest passenger forecasts at the time of the original consultation earlier this year due to June's snap general election. The updated passenger forecasts, published alongside the consultation, show that four of the five London airports - Heathrow, Gatwick, Luton, City and Stansted - are expected to be full by 2025 rather than 2029, as previously believed, and all five by the mid 2030s.
The revised air quality analysis accompanying the new draft NPS states that, up to 2029, there is a high risk that a new runway would delay the UK's ability to meet air quality limits and, even after 2030, this only falls to a medium risk. However, it also claims that compliance with air pollution limits can be achieved if measures in the air quality strategy are successful, together with effective legislation to ensure emissions from new cars are reduced under real driving conditions.
But the new air quality strategy has already been threatened with legal action by lawyers acting for campaign group ClientEarth. The Aviation Environment Federation, which also opposes Heathrow expansion, said that the draft NPS and the accompanying assessments of air quality and passenger numbers pose fundamental questions about the project's viability and have been provided at too late a stage in the process.
However, for some experts, the revised consultation changes little. Robbie Owen, head of infrastructure planning at law firm Pinsent Masons, said: "The numbers are slightly different, but the strategic case for expanding Heathrow seems as strong as ever. This further consultation will strengthen the NPS process and allow the government to say it has taken place properly and with updated information." Gideon Amos, national planning adviser at consultancy GL Hearn, agreed that the NPS would be "much safer" from legal challenge once it had been through the consultation.
However, Angus Walker, partner at law firm Bircham Dyson Bell, was not convinced. "Air quality is the biggest Achilles' heel in the Heathrow case," he said. The government has retained its pledge that planning consent will only be granted for a new runway at Heathrow if it can be delivered in accordance with the UK's air quality and climate change obligations, he noted. Pointing to the assessed high risk that a new runway would delay the UK's ability to meet air quality limits, Walker said: "The government is almost saying that the third runway can't open before 2030."