Silverstone has suffered with bad traffic delays on race days. The traffic problem was improved when the A43 Silverstone bypass was built. When the race date was moved to April in 2000] heavy rain turned the fields used for parking into mud pits, causing severe problems for the spectators trying to park. On F1 race day many spectators travel to the circuit by helicopter. Silverstone Heliport is the busiest airport in the UK for this day.