In addition to providing benefits to their users, transport networks impose both
positive and
negative externalities on non-users. The consideration of these externalities – particularly the negative ones – is a part of transport economics. Positive externalities of transport networks may include the ability to provide
emergency services, increases in land value, and
agglomeration benefits. Negative externalities are wide-ranging and may include local air pollution,
noise pollution,
light pollution,
safety hazards,
community severance and
congestion. The contribution of transport systems to potentially hazardous
climate change is a significant negative externality which is difficult to evaluate quantitatively, making it difficult (but not impossible) to include in transport economics-based research and analysis. Congestion is considered a negative
externality by economists. An externality occurs when a transaction causes costs or benefits to third party, often, although not necessarily, from the use of a
public good. For example, manufacturing or transportation cause air pollution imposing costs on others when making use of public air.
Traffic congestion Eastshore Freeway in
Berkeley, California. Traffic congestion is a negative externality caused by various factors. A 2005 American study stated that there are seven root causes of congestion, and gives the following summary of their contributions: bottlenecks 40%, traffic incidents 25%, bad weather 15%, work zones 10%, poor signal timing 5%, and special events/other 5%. Within the transport economics community,
congestion pricing is considered to be an appropriate mechanism to deal with this problem (i.e. to internalise the externality) by allocating scarce roadway capacity to users. Capacity expansion is also a potential mechanism to deal with traffic congestion, but is often undesirable (particularly in urban areas) and sometimes has questionable benefits (see
induced demand).
William Vickrey, winner of the 1996
Nobel Prize for his work on "
moral hazard", is considered one of the fathers of congestion pricing, as he first proposed it for the
New York City Subway in 1952. In the road transportation arena these theories were extended by
Maurice Allais, a fellow Nobel prize winner "for his pioneering contributions to the theory of markets and efficient utilization of resources",
Gabriel Roth who was instrumental in the first designs and upon whose
World Bank recommendation the first system was put in place in Singapore.
Reuben Smeed, the deputy director of the
Transport and Road Research Laboratory was also a pioneer in this field, and his ideas were presented to the British government in what is known as the
Smeed Report. Congestion is not limited to road networks; the negative externality imposed by congestion is also important in busy public transport networks as well as crowded pedestrian areas, e.g. on the London Underground on a weekday or any urban train station, at peak times. There is the classical excess in demand compared to supply. This is because at peak times there is a large demand for trains, since people want to go home (i.e., a derived demand). However, space on the platforms and on the trains is limited and small compared to the demand for it. As a result, there are crowds of people outside the train doors and in the train station corridors. This increases delays for commuters, which can often cause a rise in stress or other problems. A possible solution for this is fare reduction for travel at off-peak times.
Congestion pricing Gantry at North Bridge Road, Singapore Congestion pricing is an
efficiency pricing strategy that requires the users to pay more for that public good, thus increasing the welfare gain or net benefit for society. Congestion pricing is one of a number of alternative
demand side (as opposed to
supply side) strategies offered by economists to address congestion. Congestion pricing was first implemented in
Singapore in 1975, together with a comprehensive package of
road pricing measures, stringent car ownership rules and improvements in mass transit. Thanks to technological advances in
electronic toll collection, Singapore upgraded its system in 1998 (see
Singapore's Electronic Road Pricing). Similar pricing schemes were implemented in
Rome in 2001, as an upgrade to the manual zone control system implemented in 1998; London in 2003 and extended in 2007 (see
London congestion charge);
Stockholm in 2006, as seven-month trial, and then on a permanent basis since August 2007 (see
Stockholm congestion tax).
Pollution pricing From 2008 to 2011,
Milan had a traffic charge scheme,
Ecopass, that exempted higher emission standard vehicles (
Euro IV) and other
alternative fuel vehicles This was later replaced by a more conventional
congestion pricing scheme,
Area C. Even the transport economists who advocate congestion pricing have anticipated several practical limitations, concerns and controversial issues regarding the actual implementation of this policy. As summarized by noted regional planner
Robert Cervero: "True social-cost pricing of metropolitan travel has proven to be a theoretical ideal that so far has eluded real-world implementation. The primary obstacle is that except for professors of transportation economics and a cadre of vocal environmentalists, few people are in favor of considerably higher charges for peak-period travel. Middle-class motorists often complain they already pay too much in gasoline taxes and registration fees to drive their cars, and that to pay more during congested periods would add insult to injury. In the United States, few politicians are willing to champion the cause of congestion pricing in fear of reprisal from their constituents... Critics also argue that charging more to drive is elitist policy, pricing the poor off of roads so that the wealthy can move about unencumbered. It is for all these reasons that peak-period pricing remains a pipe dream in the minds of many."
Road space rationing ,
Brazil, despite no-drive days based on license numbers. Transport economists consider
road space rationing an alternative to congestion pricing, but road space rationing is considered more equitable, as the restrictions force all drivers to reduce auto travel, while congestion pricing restrains less those who can afford paying the congestion charge. Nevertheless, high-income users can avoid the restrictions by owning a second car. Moreover, congestion pricing (unlike rationing) acts "to allocate a scarce resource to its most valuable use, as evinced by users' willingness to pay for the resource". While some "opponents of congestion pricing fear that tolled roads will be used only by people with high income. But preliminary evidence suggests that the new toll lanes in California are used by people of all income groups. The ability to get somewhere fast and reliably is valued in a variety of circumstances. Not everyone will need or want to incur a toll on a daily basis, but on occasions when getting somewhere quickly is necessary, the option of paying to save time is valuable to people at all income levels." Road space rationing based on license numbers has been implemented in cities such as
Athens (1982),
México City (1989),
São Paulo (1997),
Santiago,
Chile,
Bogotá,
Colombia, La Paz (2003),
Bolivia, and
San José (2005),
Costa Rica.
Tradable mobility credits A more acceptable policy on automobile travel restrictions, proposed by transport economists to avoid inequality and revenue allocation issues, is to implement a
rationing of peak period travel but through revenue-neutral credit-based congestion pricing. This concept is similar to the existing system of
emissions trading of
carbon credits, proposed by the
Kyoto Protocol to curb
greenhouse emissions. Metropolitan area or city residents, or the taxpayers, will have the option to use the local government-issued mobility rights or congestion credits for themselves, or to trade or sell them to anyone willing to continue traveling by automobile beyond the personal quota. This trading system will allow direct benefits to be accrued by those users shifting to public transportation or by those reducing their peak-hour travel rather than the government. == Funding and financing ==