Each ferry carries 73 cars and operates using its own set of slipways and parallel chains, with a vehicle weight limit of 18 tonnes (20 tons).Frequent users can reduce the fare by half by purchasing top-ups online for a machine-readable windscreen-mounted digital payment tag, called TamarTag, which is also usable on the bridge.The fully loaded weight of each ferry is given as 1,000 tonnes, powered by up to three 12-litre diesel engines with generators feeding the two electric motors each driving its chainwheel of nearly 2 m diameter.[3] The steamboat company approached James Meadows Rendel in 1832 and asked him to design a steam-powered floating bridge for the route.A supplementary steamer service was also introduced in 1902, with the Volta and Lady Beatrice linking Torpoint to two locations in Devonport on a triangular route.[3] In July 1923 it was reported that an Asian elephant, named Julia, a part of the Bostock and Wombwell Menagerie, had swum across the river after she had broken loose and "launched herself from the ferry".[4] Motor traffic using the route increased rapidly after World War II, and two new ferries with a capacity of 30 cars each were introduced by 1961.