Policy: Definition and Typology

Congestion charging is a type of road user charge (RUC), which aims to reduce vehicle use by charging users for entering a specific zone at a given time. It is distinct from highway tolls and other types of road user charges because it is a local scheme designed to respond to local conditions (Anable and Bristow, 2007; Veitch and Bakir, 2007; EEA, 2008). There are a number of different congestion charging mechanisms including area-wide schemes where motorists pay as they cross a cordon around an area (or pay to locate within the area), toll charges on specific roads or lanes, or distance-based charges (Table 2-1.) Generally, congestion is specific to individual roadway segments, and is not a system wide phenomenon, although there are exceptions in such cities as Bangkok or Mexico City. There are two types of congestion - recurring and non-recurring. The former occurs predictably at the same place and the same time whereas, the latter arises from temporary conditions, such as a vehicle breakdown, accidents, or temporary road works. Among the central impacts of congestion are travel time unreliability, lost time incurring economic costs, and increased emissions from petrol and diesel engines caused by frequent acceleration episodes. Vehicle engines operating at low speeds also tend to emit more pollutants i.e. carbon monoxide (CO), nitrogen oxides (NOx), and volatile organic compounds (VOCs) with related impacts upon environment and human health. Related to increased emissions is the problem of increased fuel consumption and therefore carbon emissions that accompanies frequent stop-and-go driving conditions (Stopher, 2004).

Table 2-1. Typology of congestion charge policy instruments