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Multi-Modal Handbook

Parking

Parking lots are critical linkages between the transportation system and destinations. A poorly designed parking lot that does not accommodate all modes can single handedly discourage alternative modes. A well designed parking lot can transform a development into a vibrant welcoming space.

Excess parking has many direct and indirect costs. Direct costs for developers include the purchase of additional land, improvement and added maintenance costs, and property taxes. Indirect costs to a developer, but more direct costs to the environment include heat island generation and the excess stormwater runoff and loss of ground water recharge areas created by the added impervious surfaces.

Parking availability can affect not only the destination, but also the means people will use to reach a destination. The more difficult it is to find available parking, the less likely people will drive their automobiles to a destination. Lack of available parking also makes it more likely that people will utilize public transit, if it is available and relatively convenient. If there is a consistent abundance of available parking, it may indicate the parking lot is too large.

Walkways are an integral part of parking lot design.

Many off-street parking lots for commercial areas have traditionally been designed to accommodate the maximum parking loads and predominant use of single occupancy vehicles. Balancing the demands of the private sector to provide sufficient parking with the municipality's desire to reduce the harmful impacts of excess parking is an issue many municipalities must contend with in new developments.

Determining the proper size, location, and layout of parking facilities are important decisions that municipalities must make to provide the most appropriate level of parking within a municipality. Facility types generally include off-street surface parking, on-street parking, and structured parking (parking garages).

Comments

Parking facility design must reflect many factors including the amount of space available for the facility, the number of parking spaces required by the destination's land use, environmental and site specific conditions. The following provides general design principles and guidance regarding the physical elements to be addressed when developing parking facilities.

Site Work — Basic design principles to consider when deciding where parking facilities should be located include:

Number of Spaces — The Delaware Valley Regional Planning Commission (DVRPC) developed the publication The Automobile at Rest: Toward Better Parking Policies in the Delaware Valley, which inventories the parking standards of all Chester County municipalities and offers the following policy recommendations towards establishing a proper amount of parking spaces:

Pedestrian and Vehicular Circulation - The orientation and configuration of parking spaces must be considered early in the development process to create a safe and convenient facility:

Distributor Roads - In larger commercial and office developments there should be a hierarchy of travel lanes ranging from a ring road, or distributor road to parking aisles. Providing for different types of traffic improves circulation and reduces the potential for accidents.

The distributor road which is intended to carry higher speed and higher volumes of traffic throughout the development should have wider lanes, no parking, and should directly link the parking area to the public street. Distributor roads carry traffic at speeds of 10 to 20 MPH while parking aisles function at speeds of less than 10 MPH.

The intended function of the roadway immediately adjacent to a building is to be the fire lane and pick-up/drop-off area. It should not be used as a distributor road for through traffic.

Example of an internal distributor road.

Off-Street Parking

Off Street Parking
(On-lot parking)

A space located off the public right-of-way for parking a motor vehicle.

Off-street parking is the most common type of parking facility. These facilities have traditionally been developed as one large paved area resulting in expanses of asphalt. Most of these traditional lots were developed prior to the passage of modern stormwater regulations.. Parking lot designers should limit the places where pedestrians are forced to cross vehicular traffic, and reduce redundant driveways, inefficient single stacked parking bays, locations where cars need to back into intersections, limit vehicular stops and turning movements, as well as consider appropriate locations for trash enclosure pads with regard for trash vehicle turning radii.

One of the first decisions to make when designing a parking facility is to determine the safest and most efficient configuration of the available space to meet the parking requirements. There are a number of different parking angle configurations to be considered, including perpendicular (or 90 degree) and other angled (60, 45, 30 degrees) options. The following provides basic descriptions and dimensions including the advantages and disadvantages for each configuration type:

Perpendicular (90 degree) - This is the most efficient and economical parking configuration because it accommodates the most vehicles per square foot of available parking area. Perpendicular configurations work best with two-directional driveway aisles; one way drive aisle configurations have almost the same space requirements and offer little advantage in circulation. Standard dimensions for this configuration are 9 foot wide by 18 foot deep spaces with a 24 foot wide (two-directional) driveway aisle for a total 60 foot wide cross section.

Advantages

Disadvantages

Angled—60 Degree - The primary advantage with any angled parking is the ability to provide more spaces or better circulation patterns when the space available for parking is dimensionally constrained. The 60 degree angled parking configuration is ideal for a fast turnover rate or predominantly short term use and may be preferred over 90 degree parking in some situations due to ease of navigation, even though it may be a less efficient use of the available space. Standard dimensions for this configuration are 9 foot wide by 20 foot deep spaces with a 24 foot wide (two-directional) driveway aisle for a total 64 foot wide cross section, or 16 foot wide (one-directional) driveway aisle for a total 56 foot wide cross section.

Advantages

Disadvantages

Angled—45 Degree - The 45 degree angled parking configuration displays similar benefits and limitations as the 60 degree configuration. Standard dimensions for this configuration are 9 foot wide by 19 foot deep spaces with a 14 foot wide (one-directional) driveway aisle for a total 52 foot wide cross section. Two-directional driveway aisle dimensions are not provided since two-directional 45 degree parking requires almost the same amount of cross section width as 90 degree configurations while providing significantly fewer spaces.

Advantages

Disadvantages

Angled—30 Degree - Similar to 45 degree configurations, this configuration progressively increases the amount of pavement required per space while narrowing the double bay cross section. Standard dimensions for this configuration are 9 foot wide by 16.5 foot deep spaces with a 12 foot wide (one-directional) driveway aisle for a total 45 foot wide cross section.

Advantages

Disadvantages

Landscaping - The most attractive,most functional, and most sustainable parking areas are those that are well landscaped. Trees provide valuable additions to parking areas, whether planted in curbed islands or located on the parking area perimeters. Trees provide shade, visually reduce the mass of open pavement, and mitigate heat gain. Landscaped areas may be used to collect runoff for stormwater management. The following are some general considerations for how plant materials can be used to improve parking facilities:

Other factors to consider:

Avoid the following with respect to tree plantings:

A good example of trees and planted
islands within a commercial parking lot.

Trees that should be selected include those that:

See also LANDSCAPE MATERIAL design element.

Lighting - Lighting is an important component of parking lot safety, especially for a facility that has early morning, late afternoon, or night time use. The Illuminating Engineering Society (IES) recommended minimum average illumination level for a surface parking lot is 0.5 footcandles. The IES also recommends that all pedestrian routes and entrances/exits should be well lit with a minimum average of 1.0 footcandles. Lighting poles are typically 20-25 feet in height, and should be located in islands or in parking perimeters and protected from potential vehicular damage.

Other lighting factors to consider include:

See also LIGHTING design element.

Example of vegetated bioswales within parking islands
at Riverfront Park, Pottstown, PA.

Stormwater Management - Surface parking lots have traditionally been developed with large expanses of asphalt resulting in a significant increase in stormwater runoff. The stormwater was then collected by a drainage system where runoff from large storm events would be temporarily stored in a retention basin then slowly released through control structures into the natural drainage systems. This general concept has been revised and reflected in Pennsylvania through the State's adopted erosion and sediment control regulations where the focus is to infiltrate or recharge a much larger portion of this runoff into the ground. As part of this shift, the National Pollutant Discharge Elimination System (NPDES)-as authorized by the federal Clean Water Act-now requires a permit for any earth disturbance exceeding 1 acre, where the threshold was previously 5 acres. These permit applications are reviewed by the local Conservation District as part of the land development process.

To help facilitate these new regulations, the state has published the Pennsylvania Stormwater Best Management Practices Manual. Some examples of Best Management Practices (or BMPs) applicable to surface parking include:

Parking lot with a large expanse of uninterrupted paving.

Shared Use Parking - 'Shared Use' parking is the approved use of the same off-street parking spaces for two (2) or more uses where peak parking demand of the different uses occurs at different times of the day, or, where various uses are visited without moving the automobile; and, where the division of parking spaces is a net decrease from the combined total of individual off-street parking requirements for each use.

Municipalities should consider possibilities for shared parking facilities based on operating hours and peak parking times for adjacent or nearby uses. Through the use of shared parking facilities, a lower overall number of parking spaces may be justified. Municipalities should be assured that adequate parking facilities for all uses will continue in the long-term and be available regardless of individual land use changes.

Areas where excess parking is provided should be considered for use as a park and ride facility for public transportation. See also the PARK-AND-RIDE design element.

On-Street Parking

On-Street Parking
(Parking lane)

An area within the right-of-way and adjacent to the travel lane for parking motor vehicles.

Standards

AASHTO: The minimum width of a parking lane is 8 feet. The desirable width is 10 to 12 feet.

PennDOT:

See also the LANE DESIGN design element

Comments

It can generally be stated that on-street parking decreases through capacity, impedes traffic flow and increases accident potential (AASHTO). From a comprehensive review of accident data, curb parking is directly or indirectly responsible for at least one out of every five accidents that occur on surface streets in our cities each year (ITE). While this applies to the nation's urban centers it must be taken into account when designing on-street parking anywhere.

The type of on-street parking selected should depend on the specific function and width of the street, the adjacent land use and existing and anticipated traffic volumes.

On-street parking is most commonly associated with urban or village landscapes and is often metered as a revenue generator as part of a community's parking management program. On-street parking spaces are typically included in the design of the roadway within which they are located and also referred to as 'parallel' parking.

On-street angled parking is less common and often associated with historic or central business districts with lesser traffic volumes where it also serves as a traffic calming effect. These installations require much more space within the road right-of-way than parallel parking but offer the opportunity to create more stalls within the same length.

Back-in angled on-street parking has recently been installed in the Borough of Pottstown, Montgomery County, PA. This installation on East High Street converted two westbound travel lanes and on-street parallel parking into one westbound lane, one bike lane and back-in angled parking within the same available space. Installed in 2003, this concept "has helped revitalize the downtown by slowing traffic, providing more parking spaces adjacent to stores, encouraging bicycling, and making it easier for pedestrians to cross the street."

ADA Accessibility & Parking Requirements
(aka Handicapped parking and access)

All or any portion of buildings, structures, site improvements, complexes, equipment, roads, walks, passageways, parking lots, transportation facilities, or other real or personal property that are readily accessible to and usable by individuals with disabilities in terms of architecture and design, transportation and communication.

ADA Accessibility & Parking Requirements

ADA accessible parking.

The Americans with Disabilities Act (ADA) Accessibility Guidelines for Buildings and Facilities requires that the construction of all new facilities shall provide at least one accessible route within the boundary of the site from public transportation stops, accessible parking spaces, passenger loading zones if provided, and public streets or sidewalks, to an accessible building entrance. And, at least one accessible route shall connect accessible buildings, facilities, elements, and spaces that are on the same site. The accessible route shall be a minimum of 36 inches wide. The routes should be as close to the designated handicapped parking spaces as possible. See also the ADA ACCESSIBILTY design element.

The minimum number of accessible parking spaces to be provided is based on the total number of spaces included:

Total number of parking spaces provided in parking facility Minimum number of required accessible parking spaces
1 to 25 1
26 to 50 2
51 to 75 3
76 to 100 4
101 to 150 5
151 to 200 6
201 to 300 7
301 to 400 8
401 to 500 9
501 to 1000 2% of total
1001 and over 20, plus 1 for each 100, or fraction thereof, over 1000
ada parking
Source: ADA Accessibility Guidelines for Buildings and Facilities

Accessible parking spaces serving a specific facility should be located closest to an accessible entrance. If facilities have multiple accessible entrances, accessible parking spaces should be dispersed and located closest to the accessible entrances.

Accessible parking spaces should be at least 8 feet (96 inches) wide. Parking access aisles should be part of an accessible route to the facility entrance. Two accessible parking spaces may share a common access aisle at least 5 feet wide, with the potential for the aisle to be 8 feet minimum width if shared with accessible van parking. Parked vehicle overhangs should not reduce the clear width of an accessible route. Parking spaces and access aisles should be level with surface slopes not exceeding 1:50 or 2% in all directions. Signing for parking spaces should be placed on the paving surface and meet the requirements of the law.

Structured Parking

Structured Parking
(Parking garage)

A building constructed primarily to provide for many levels of off-street parking to meet high parking demands.

Parking garages are most commonly associated with densely developed urban centers and represent a significant investment in providing for a parking facility. They may also be developed at locations that have a significant draw with little or no additional space available to provide for more surface parking to meet the parking demands. Examples of such locations include transportation centers, rail stations, shopping malls & centers, and significant employment centers.

There are many design factors to consider for structured parking, including:

Garage
West Chester Borough's Chestnut Street parking structure with Solar Array.

Recommendations

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The entire Multi-Modal Handbook PDF may be downloaded here.