The public transit system in Frankfurt is part of the Rhein-Main-Verkehrsverbund (abbreviated: RMV) transport network and consists of several carriers who all use the same fare system. Therefore, one ticket is valid for a journey which may include several modes of transit run by different operators. The fares are paid in advance of travel at a ticket vending machine or at the driver on board a bus. There are no turnstiles or other controlling barriers - passengers therefore have responsibility for ensuring they have a ticket. Plain-clothes ticket inspectors are employed and carry out checks to ensure passengers have paid. If found to be travelling without a ticket, then they are required to pay an increased fare of €60. A single way trip within Frankfurt costs between €1.80 and €2.80, and a journey to the suburbs outside Frankfurt costs between €4.65 and €9.10 approx. There are also some discounts for children for groups or day tickets. A day ticket for traveling within Frankfurt costs €7.
Frankfurt itself is the central city of the so-called Rhein-Main Region, and therefore the service caters the large number of commuters who travel to and from the suburbs each day. The suburban rail service is provided by rapid transit trains (S-Bahn). All but one of the lines run together in a single underground section through the city centre, and then go their separate ways at either end. In the suburban sections they are generally double-tracked or share mainline tracks with other regional, long distance passenger and cargo trains.
The trains can be up to 200 m (600 ft) long and have a maximum speed of approximately 140 km/h (90 mph). Electricity supply is provided by overhead wires at the common German railroad voltage (15,000 volts AC).