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

efficiently locate spaces.
Transportation’s Role in Reducing U.S. Greenhouse Gas Emissions: Volume 2
Most parking management strategies are under the domain of local government. In most
U.S. cities, parking supply is constrained or priced only in the central business district
(CBD) and possibly a few other major activity centers, primarily as a result of market
forces that establish a strong premium on land costs. Outside of these areas, parking
supply is generally plentiful, due to long-established planning and zoning regulations that
require developers to provide ample parking, and free (Shoup, 2005). However, some
cities, such as Charlotte, Portland, Oregon, and Pasadena, have taken steps to reduce
parking supply in transit-oriented developments or other urban neighborhoods. Active
management of parking pricing to regulate demand is being tested in New York and
Washington, D.C. and considered in other cities including Chicago, Los Angeles, and San
Francisco (Nguyen, 2009). Parking cash-out and worksite parking pricing can be
implemented by employers or property managers, and are considered a subset of
employer commute measures (Section 5.5) in this report.
Magnitude and Timing of GHG Reductions
Both the cost and supply of parking are significant determinants of travel behavior. (These
factors tend to be closely related, as parking tends to be priced when – and only when – its
availability is limited.) Most studies of parking pricing have focused on commuting
behavior. Cervero (1993) found that rail transit mode shares in the San Francisco Bay Area
increased by about 50 percentage points (e.g., 64 versus 14 percent transit mode share) if
the employee had to pay for parking, compared to those that were given free parking. A
study of employers in California found that parking cash-out programs reduced vehicle
trips an average of 11 percent (Shoup, 1997).
Information on the potential nationwide GHG reductions from parking pricing or other
parking management strategies is very limited. Two recent estimates have focused on
commute travel in particular. Nationwide, only 5 percent of employees pay for parking,
so in theory there is great potential for expanding the scope of worksite-based parking
pricing. On the other hand, market prices for parking usually exist only in CBDs and other
densely built activity centers, and, according to data from the 2000 U.S. Census, less than
10 percent of a typical metropolitan area’s workforce is located in the CBD. Assuming that
an additional 5 percent of workers nationwide could have parking priced at market rates,
reducing SOV use per worker by 20 percent, and further assuming that work trips make
up 30 percent of total VMT, the total reduction in VMT on a nationwide basis would be
approximately 0.3 percent (EEA, 2008). This represents a reduction of 3.5 mmt CO2e in
2030. A nationwide fee of $5 daily per parking space levied on all worker-utilized parking
spaces (or the equivalent, such as a $5 cash-out incentive offered to all workers who choose
not to drive) is estimated to reduce emissions much more substantially—by nearly 40 mmt
CO2e in 2030 (Cambridge Systematics, 2009). However, it is not clear how such a broadbased
fee would be implemented or enforced.
Some parking management strategies, such as market-rate pricing of on-street spaces or
offering a cash-out option to employees, can be implemented within one or two years.
However, others (such as reducing parking requirements in zoning) take many years to
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