Transportation's Role in Reducing U.S. Greenhouse Gas Emissions ...

Transportation’s Role in Reducing U.S. Greenhouse Gas Emissions: Volume 2
achieved through the pricing alone (although there will be some offsetting increases in
GHG emissions from the additional transit service). The reduced congestion as a result of
cordon pricing should also improve fuel economy, achieving further greenhouse gas
reductions. On the other hand, it may result in more traffic and congestion outside of the
congestion pricing zone, leading to GHG increases in these areas.
Magnitude and Timing of GHG Reductions
Cordon or area pricing has been found to result in a significant reduction in VMT and
congestion in the few central city areas to which it has been applied. In London,
21 percent less traffic entered the central zone in 2006 than in 2002 before the application of
cordon pricing. This resulted in an estimated reduction in CO2 emissions of 16 percent in
the pricing zone, of which about half was due to changes in traffic volume and half due to
changes in speeds (Transport for London, 2007). Stockholm’s pricing scheme was
estimated to reduce CO2 emissions by 10 to 14 percent in the inner city, or 2 to 3 percent on
a countywide basis (KT Analytics 2008). A modeling study estimated that an $8 fee
applied to all traffic entering the Manhattan central business district could reduce traffic in
this area by 7 percent (NYCEDC and NYCDOT, 2007).
Cordon/area pricing has limited overall effectiveness, however, because it only applies to
a small amount of total travel. The application of cordon pricing to all CBDs nationwide is
estimated to affect only 3 percent of urban VMT, 14 reducing GHG emissions by 1.6 to
3.2 mmt CO2e in 2030 (Cambridge Systematics, 2009). This estimate considers only VMT
reduction effects and not the GHG benefits of congestion reduction.
Furthermore, cordon/area pricing could have the negative impact of shifting travel to
routes which bypass the selected cordons, thus increasing some trip lengths and travel
times and reducing any GHG benefits from reduced travel into the CBD. In the long term,
applying pricing only to CBDs could also impact development patterns. A recent study of
the Washington, D.C. metropolitan area used an integrated transportation and land use
model to evaluate the effects of both downtown and beltway cordon pricing, including
land use as well as travel changes. The study found an overall regional VMT reduction in
the range of 0.8 to 1.3 percent (Safirova, Houde, and Harrington, 2007). GHG reductions
(which were not analyzed) are likely to be greater because of the benefits of reduced
congestion.
Cordon/area pricing can be implemented in the short term (less than five years), with
immediate impacts. Tolls may need to be continually adjusted after the project is
implemented, in order to keep congestion to economically efficient levels.
14 The three percent estimate is based on an estimate of urban VMT in the greater London region
affected by London’s cordon pricing system (Transport for London, 2007).
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