Restricted access to zones

Access regulation zones are frequently called low emission zones (LEZs) or environmental zones. An LEZ is a defined area that can be entered only by vehicles meeting certain emissions criteria or standards. Depending on the design and objective of the zone, vehicles that are prohibited are typically relatively more polluting vehicles. The main objective of such zones in urban areas is often the reduction of pollutant emissions, such as particulate matter (PM). LEZs should be adjusted over time to account for changes in road use/demand within the restricted zones.

Low-emission zones have been introduced in many European cities as well as in Tokyo (Japan) and Singapore. Frequently, such zones are introduced in combination with economic measures like congestion pricing, and are coupled with a zone that restricts the access of heavy-duty vehicles (HDVs) or freight transport. Examples of access restriction zones that have the primary objective of reducing CO2 emissions could not be identified.

In European cities, the criteria for LEZ entrance are based upon the Euro emission standard, the year of first registration as a proxy, or by means of the presence of retrofitted emission-control devices, usually a diesel particulate filter (DPF). Only HDVs are restricted in most European countries, but in Germany light-duty vehicles (LDVS) are included, as are cars in Athens (Greece), London (UK) and Lisbon (Portugal). The Italian LEZs also restrict two-wheeled vehicles. There are a large number of LEZs in Italy and Germany, and several in the United Kingdom, but other countries have been less enthusiastic.

Available studies on health impacts and local pollutants can be divided into two major groups: studies modelling hypothetical situations and monitoring studies measuring the impact of actual LEZs. In some cases, both observations and modelling techniques are applied. Studies that rely on modelling tend to overestimate the positive effect of LEZs on local pollutant concentrations.