Civil Engineering Reference
In-Depth Information
commuters who drove downtown to switch to transit. By the early 1980s, the
effective management of parking was recognized an effective strategy to achieve
travelers and community objectives as well as manage congestion [
5
].
22.2.2 Objectives of Parking Management
Parking management, as de
ned in this chapter, is the comprehensive control of the
quantity, location, price, and availability of parking. Parking supply and demand
strategies include (1) limiting and controlling parking supply, (2) expanding park
and ride facilities for transit and carpool riders, (3) providing preferential parking
spaces for high occupancy vehicles, and (4) establishing pricing incentives. An
acceptable mix of these strategies can help reduce congestion by encouraging peak
period commuters to use transit or ride share.
22.2.3 Limiting Parking Supply
Historically, municipal parking codes established
minimum
parking ratios (number
of spaces per unit of development) to ensure suf
cient off-street parking, accom-
modate a site
s needs and avoid spill back onto public streets or neighboring sites.
Typical values were codi
'
guides published by
public agencies and the Institute of Transportation Engineers. More recently,
parking requirements are sometimes framed as the
maximum
allowable parking
rates, rather than minimum rates.
Transit oriented cities have increasingly recognized that a large supply of
commuter parking in central areas has a negative impact on transit ridership and
contributes to downtown congestion.
Analysis of modal choices in eight major Canadian cities, for example, found a
strong inverse relationship between downtown transit use and employee parking
supply [
8
]. Table
22.1
shows that A.M. peak hour transit share increases as the
number of parking spaces per employee decreases.
A non-linear regression model found an r-square value of 0.92 for the equation
explaining transit use to US and Canadian CBDs as a function of downtown
parking supply per employee. But when US cities were included the relationship
was much weaker yielding an r-square was 0.59 [
8
].
Accordingly, since the 1970s some larger cities in the United States and Canada
have limited their downtown parking supply as a means of reinforcing transit
ridership and reducing automobile use. The share of automobile trips was reduced
by establishing ceilings on the parking supply and/or by modifying zoning
requirements. These parking supply restraints work in a compact and densely
developed CBD that is well served by public transit, and where there is the need to
limit traf
ed in various
“
parking generation
”
c congestion.
