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== Introduction ==
[[File:Expresslanes.jpg|thumbnail|right|View of Los Angeles Metro ExpressLanes (credit: LACMTA)]]
Congestion pricing is a concept applied to roadways experiencing high traffic volumes in order to motivate better economic decision making among drivers and improve traffic flow. When a roadway is carrying more vehicles than it was designed for, traffic becomes congested, decreasing travel times and reliability of travel. Applying a pricing scheme, such as a toll, which increases along with congestion (and likewise decreases), motivates some drivers to adjust their travel behavior. Drivers unwilling to pay the higher price will choose to drive at other times, thus maintaining or improving overall congestion conditions.
Congestion pricing can be used to generate revenue in support of enhanced public transit service. Recently implemented projects demonstrate that congestion pricing is an effective tool
both for managing vehicle throughput and motivating solo drivers to choose improved transit options.
== Congestion pricing basics ==
Congestion pricing encompasses several different strategies for applying a price to heavily traveled road networks. The basic concept is to raise the price of travel as the number of travelers increases, especially when the level of traffic begins to decrease the time and reliability of travel. In the United States, "high occupancy toll" (HOT) lanes has recently become one of the most common forms of congestion pricing<ref>Federal Highway Administration. "Congestion Pricing: A Primer". October 2008. http://ops.fhwa.dot.gov/publications/fhwahop08039/cp_prim1_00.htm</ref>. HOT lanes are typically converted from existing high-occupancy vehicle (HOV) lanes, retaining the basic concept of free travel by carpools and buses, while adding the option for solo drivers to "buy in" to the lane. This strategy allows motorists who value a faster and more reliable trip on the highway to pay for such an alternative. HOT lanes do not replace the "general purpose" lanes, meaning people can continue to drive for free on the same roadway. True congestion pricing on HOT lanes requires that the price paid by solo drivers increase as the volume of cars increases
. In some examples, the policy guiding price response is based on maintaining a minimum average speed in the HOT lanes, such as 55mph. If so many vehicles are buying into the HOT lanes that traffic begins to back up, the price may climb significantly, or in some cases, the HOT lanes may revert temporarily back to HOV-only. There are several ways this can be accomplished, which are explored in the examples below.
Other congestion pricing tools besides HOT lanes include "cordon pricing", variable tolls across an entire roadway, and certain non-tolling strategies. Cordon pricing has been used in London since 2003, in which most vehicles entering the central city must pay a charge between 7:00am and 6:30pm Monday through Friday. The revenues from the cordon price were directed towards improved public transport, and together have reduced traffic by as much as 15% without significant increases on surrounding local roads. Cordon pricing is not currently used anywhere in the United States, although a plan had been developed to enact cordon pricing around Manhattan (CITE).
== Examples of Congestion Pricing ==
=== California ===
=== Elsewhere ===
"Transit and Congestion Pricing: A Primer". http://www.ops.fhwa.dot.gov/publications/fhwahop09015/cp_prim7_00.htm
== References ==