It is necessary for taxi-drivers to obtain a special licence, which then allows them to stand in taxi ranks or to drive around looking for passengers. The taxi-driver assists the passengers with any luggage they may have and then drives them to their destination. They then collect the fare as shown on the taximeter. They make sure the taxi is kept clean, both inside and out, and are also responsible for ensuring the taxi is properly maintained and kept in a roadworthy condition. Private hire vehicle drivers perform the same function as a taxi driver, but are not allowed to stand in taxi ranks or ply for trade on the streets: they are normally booked by phone, or by two-way radio from a central booking office.