Heathrow’s proposed £33bn third runway could add 100,000–200,000 daily passengers, increasing pressure on roads and rail. Transport for London is questioning whether the expensive Heathrow Express should continue, arguing that its limited use takes up valuable railway capacity that could support cheaper, more frequent public transport.

The Heathrow Express costs £26 for a 15–21-minute journey and carried 4.5 million passengers last year—fewer than 6% of Heathrow’s air passengers, including discounted airport staff. TfL favours expanding the Elizabeth line, which reaches more of London at lower fares, although services to Terminal 5 are currently infrequent and rail capacity remains constrained.