Plan extra time during rush hour; roads leading to Heathrow, including the M4, often experience congestion

https://jeffreyyubo860.cavandoragh.org/heathrow-express-vs-elizabeth-line-fastest-way-to-heathrow-from-central-london

Plan extra time during rush hour; roads leading to Heathrow, including the M4, often experience congestion, especially around junctions and airport exits.