Geoscience Reference
In-Depth Information
There is a large body of literature dealing with parking-policy measures. Several
researchers stress the need for combined urban-land-use and transportation
planning in order to reduce private VKT and, consequently, pollutant emissions.
Several studies show that parking-policy methods have but a small influence on
VKT, and therefore they are more useful when combined with urban-land-use and
transportation planning policies. The main claim is that parking policies do not
much affect private VKT unless the use of public transit is encouraged and the
urban structure is amenable for choosing alternative modes (Marsden
2006
;
Marsden and May
2005
).
An interesting point of view elaborated by Shoup (
1999
) shows the importance
of parking-policy methods as a catalyst for further implementation of urban land-
use-development and transportation planning policies. The author describes a
vicious cycle, briefly outlined below, that enhances VKT.
This cycle starts with transportation planners who survey parking occupancy
at sites that offer ample free parking but lack public transport. The parking-
generation-rate manuals created by transportation engineers are used by urban
planners to set the minimum number of parking spaces for all types of land uses.
When the parking supply is large, most new developments will offer free parking.
Transportation planners survey vehicle trips to and from sites that offer free
parking, and the outcome of this procedure is a trip-generation-rate manual. The
roads leading to such sites are designed and planned according to these manuals,
which means that the roads and highways provide enough capacity to satisfy
expected demand. Urban planners generally limit land-use density in order to
prevent congestion on roads near a new project because of their limited capacity
(Shoup
1999
).
This vicious cycle demonstrates the huge cumulative effect that parking policy
has on urban land-use and transportation planning. Shoup (
1999
) stresses the
importance of parking policy as a means of influencing transportation land use
and urban planning in a significant way, not simply as a “glue” connecting the urban
land use and the transportation system (Shoup
2005
). Note, as previously men-
tioned, that most researchers refer to parking policy as a component of the whole
complex of transportation land-use-development and urban planning policies.
Since urban land-use and transportation planners seldom have the opportunity to
plan from scratch in a completely new setting, joint planning of a transportation
cum land-use policy is rare. Usually planning is undertaken in the framework of
a new neighborhood site in an existing city. Therefore, there are usually leading
land-use policies that are adopted first. Thus, in order to reduce VKT (and, hence,
air-pollutant emissions), a leading policy, such as parking policy, could trigger and
affect other aspects of urban form, land use, and transportation planning aimed at
reducing VKT (Cervero
2002
).
The problem with adopting any policy measure is that it often draws a large
amount of public criticism if not backed with solutions that will alleviate, at least in
part, the policy's perceived restrictions on the general public. For example, when
enforcing parking-policy measures such as increased parking fees and/or decreased
numbers of parking spaces, the public will demand the provision of alternative and
