<P> The driver of a motor vehicle is typically required to hold a valid driver's license while driving on public lands, whereas the pilot of an aircraft must have a license at all times, regardless of where in the jurisdiction the aircraft is flying . </P> <P> Vehicles are often required to be registered . Registration may be for purely legal reasons, for insurance reasons or to help law enforcement recover stolen vehicles . Toronto Police Service, for example, offers free and optional bicycle registration online . On motor vehicles, registration often takes the form of a vehicle registration plate, which makes it easy to identify a vehicle . In Russia, trucks and buses have their licence plate numbers repeated in large black letters on the back . On aircraft, a similar system is used where a tail number is painted on various surfaces . Like motor vehicles and aircraft, watercraft also have registration numbers in most jurisdictions, however the vessel name is still the primary means of identification as has been the case since ancient times . For this reason, duplicate registration names are generally rejected . In Canada, boats with an engine power of 10 hp (7.5 kW) or greater require registration, leading to the ubiquitous "9.9 hp (7.4 kW)" engine . </P> <P> Registration may be conditional on the vehicle being approved for use on public highways, as in the case of the UK and Ontario . Many US states also have requirements for vehicles operating on public highways . Aircraft have more stringent requirements, as they pose a high risk of damage to people and property in event of an accident . In the US, the FAA requires aircraft to have an airworthiness certificate . Because US aircraft must be flown for some time before they are certified, there is a provision for an experimental airworthiness certificate . FAA experimental aircraft are restricted in operation, including no overflights of populated areas, in busy airspace or with unessential passengers . Materials and parts used in FAA certified aircraft must meet the criteria set forth by the technical standard orders . </P> <Table> <Tr> <Td> </Td> <Td> This section does not cite any sources . Please help improve this section by adding citations to reliable sources . Unsourced material may be challenged and removed . (July 2011) (Learn how and when to remove this template message) </Td> </Tr> </Table>

When is a vehicle considered parked in europe