This article is about buses that can operate from two independent fuel sources. For other hybrid technologies, see
Hybrid electric bus and
Fuel cell bus. For vehicles for two infrastructure types, see
Dual-mode vehicle.
A dual-mode bus is a
bus that can run independently on power from two different sources, typically electricity from
overhead lines like a
trolleybus or from
batteries like a
hybrid bus, alternated with conventional
fossil fuel (generally
diesel fuel). In contrast to other hybrid buses, dual-mode buses can run forever exclusively on their electric power source (wires). Several of the examples listed below involve the use of dual-mode buses to travel through a tunnel on electric overhead power.
Many modern trolleybuses are equipped with auxiliary propulsion systems, either using a small
diesel engine or battery power, allowing movement away from the overhead wires, called "off-wire" movement, but such vehicles are generally not considered to be dual-mode buses if their off-wire capability is very limited. Examples include the fleet of about 300 trolleybuses in
San Francisco[1] and the trolleybuses used on a 2005-opened system in
Rome, Italy,[2] which are capable of running on battery power only for short distances or short periods of time before needing recharging. The Rome vehicles are powered from overhead trolley wires over most of the 11.5-km route and only use battery power on the 500-metre section closest to the city centre.[2] Dual mode trolleybuses in a number of Chinese cities can operate significant distances (8 to 10 km) off-wire on battery power.[3]
Boston, Massachusetts, USA installed dual-mode Neoplan DMA-460LF buses on the Waterfront portion of its
Silver Line in 2005 and removed in 2023. Electric power was required in the exclusive right of way that runs in a tunnel under
Fort Point Channel to
South Station;
diesel power was used to run on city streets and highways, including the
Ted Williams Tunnel to
Logan Airport
Castellón de la Plana, Spain installed a new trolleybus line that went into operation 25 June 2008.[5][6] The
Irisbus Civis vehicles are optically guided and are capable of switching to diesel engine power for turning in front of the Parque Ribalta.[7][8]
Ploiești,
Romania features ex-Lausanne Neoplan N6121 dual-mode buses in the Ploiești trolleybus system.
São Paulo,
Brazil also has a dual bus that operates in the
Jabaquara district, in the south zone. One of these is a Superarticulated Bus that operates in the
Corredor ABD.
Gdynia and
Lublin, both
Poland have the dual-mode buses running as part of their
trolleybusnetworks, in case of Gdynia, their (PKT's) duobuses are
Solaris Trollinos and
Mercedes Citaros (which were converted into trolleybuses in 2012). Both of these types, unlike typical dual-mode buses, are trolleybus and
electric bus hybrids.