road congestiona situation where the volume of traffic using certain roads is high enough to slow traffic flows, causing delays to all travellers journeying on those roads. Road congestion has increased in many countries as a result of greater car ownership and use, and is particularly prevalent in cities and urban areas, especially in the ‘rush hours’ at the start and end of working days as commuters travel to and from work. The main costs of road congestion are the time delays experienced by road travellers, which, in the case of lorry and van drivers, salespeople, etc., is borne by their employers. In addition to lost time, slow-moving vehicles burn more fuel to complete their journeys and cause more exhaust POLLUTION.
Congestion is an example of MARKET FAILURE, with each extra vehicle using a congested road slowing traffic for all vehicles, so imposing a social cost of EXTERNALITY on other road users in the form of delays. To correct for this externality, governments have several options. First, they could build more roads or widen or improve existing roads, at public expense, to increase road supply. However, this may generate further traffic as faster journeys encourage more consumers to buy cars or to live farther from their places of work. Second, governments can build roads and bridges financed by tolls paid by motorists. Third, government can subsidize public transport as substitutes for cars, such as buses, trains and trams, to encourage their greater use by travellers. Fourth, governments can restrict car access by designating bus-only lanes and introducing parking charges. Finally, governments can use road-pricing systems to charge vehicles for travelling on designated roads at specified times in order to discourage car use. For example, in 2003 London introduced a congestion charge of £5 per day for vehicles entering the central London charging zone, which has initially reduced traffic by around 20%. Since 1998 Singapore has had a more sophisticated electronic road-pricing scheme, which charges different rates for travel in different areas of Singapore at different times.