Pure electric vehicles: wholly driven by an electric motor, powered by a battery that can be plugged into the mains and have no combustion engine. These vehicles do not produce any tailpipe emissions and usually only need a single gear. Sometimes referred to as Batter Electric Vehicles (BEV). Plug-in hybrids: features a combustion engine and an electric motor, with the electricity supplied by a battery pack. The electric motor can power the car for part of its journey before the combustion engine starts up. It can be plugged in to charge its batteries. Sometimes referred to as Plug In Hybrid Vehicles (PHEV). Extended-range electric vehicles (E-REV): have a plug-in battery pack and electric motor, as well as an internal combustion engine. The difference with a plug-in hybrid is that the electric motor always drives the wheels, with the internal combustion engine acting as a generator to recharge the battery when it is depleted. Hydrogen fuel cell vehicles: have a fuel cell stack which uses hydrogen to produce electricity, which then powers the wheels of the vehicle. They have no internal combustion engine and do not need recharging. They will continue to generate power as long as they are fed with a supply of hydrogen and are refuelled at a filling station in a similar way to vehicles with a petrol or diesel engine. An initial network of 12 hydrogen filling stations is being developed across in the UK to support their roll out.