A low-emission zone (LEZ) is a defined area where access by some polluting vehicles is restricted or deterred with the aim of improving air quality. This may favour vehicles such as bicycles, micromobility vehicles, (certain) alternative fuel vehicles, hybrid electric vehicles, plug-in hybrids, and zero-emission vehicles such as all-electric vehicles. A zero-emission zone (ZEZ) is a LEZ where only zero-emissions vehicles (ZEVs) are allowed. In such areas, all internal combustion engine vehicles are banned; this includes any plug-in hybrid vehicles which cannot run zero-emission. Only battery electric vehicles and hydrogen vehicles are allowed in a ZEZ, along with walking and cycling and fully electric public transport vehicles, e.g. trams, electric buses etc. Workings In many LEZs, vehicles that do not meet the emission standards set by the LEZ are not barred from entry into the LEZ (i.e. using automated boom barriers), but rather simply fined if they enter the zone. A fine is not issued if entering the LEZ with a vehicle that does not meet the emission standards, when a fee (LEZ daily charge, ...) has been paid. In some LEZs, such as the one in London, this is done by automatic number-plate recognition (ANPR) cameras which read the vehicle registration number plate as they enter the LEZ and then compare it against a database of vehicles which: either meet the LEZ emissions standards, or are either exempt or registered for a 100 percent discount, or if the LEZ daily charge has been paid This fee/fine works as a deterrent for those having a vehicle that does not meet the LEZ emission standard for entering the city, and those having such vehicles will hence try to avoid paying this fee/fine (using various means, see "intent and actual impact"). Intent and actual impact The intent of LEZs is generally to improve air quality within cities. This intent is indeed achieved, with diesel particulates (PM10) dropping in most LEZs. Often, this is achieved as people with polluting vehicles replace them with vehicles that attain a higher emission standard, which may mean buying a new vehicle. Some people (such as workers on night shift or carrying heavy tools or cargo) however can't do without a car, but might not be able to afford to purchase unsubsidized cleaner vehicles. Therefore in some places the LEZ is only enforced when public transport is available, or electric taxis or cargobikes are subsidized. The European Federation