Circuit marshals monitor the events to ensure everyone on track is kept as safe as possible. You don't need any special sort of licence, but do require a full and valid driving licence. Most racing licences are also accepted. Most car track days run in an open pitlane format, where drivers can come on and off the track as they please. Sometimes car track days are run in groups, where drivers are split into beginner, intermediate and advanced ability and will take turns out on track. Usually in one 15 - 20 minute session per hour for each group. On most events you can have extra drivers and passengers, hire garages and helmets and also book a session of tuition.