U.S. Parking Structures Continue their Evolution
Laura Barbero-Buffa and Robert A. Chapman
U.S. parking structures are as varied and unique as the destinations they serve and the density of the area in which they are located. Their form and architecture reflect their users. For example, distinct differences exist between parking garages that serve suburban office workers or retail shoppers, and visitors to the downtown urban core.
The size and design of these structures also are affected by factors including the location, whether the structure qualifies as shared parking, cost and availability of different building materials, and the available parking technology. In the retail and municipal markets, parking structures exhibit a high turnover and a small number of repeat users.
Thus, the typical parking stall is 18 feet deep by 9 feet wide, with drive aisles that are, at a minimum, 24 feet wide for two-way traffic. Most parking structures provide straight-in parking (90° stalls), and when angled parking is provided for convenience, the stalls tend to have an angle between 60° and 70°. To ensure a more intuitive and comfortable parking experience, park-on ramps are provided and the slopes are usually limited to 5% to 6%. Adequate height clearances of 7 to 8 feet, as well as bright lighting, provide patrons with a sense of openness and safety.
U.S. parking structures average approximately 20% larger dimensions for accommodating vehicles than their European counterparts. However, the United States may be moving toward accommodating smaller vehicles as awareness of environmental issues with fossil fuels and their finite availability becomes more widely accepted.
Also, ramping systems are becoming more sophisticated to express users to available parking, rather than circulating through areas of unavailable parking. Dynamic signs display the quantity of available spaces for each level, and the user can proceed directly to the available parking area, staying clear of occupied areas.
Large quantities of available land in urban and suburban areas formerly gave developers flexibility with regard to garage footprint, and below-ground construction was limited to parking structures in high-density cities such as New York and Chicago. However, for the past decade, land costs have been steadily rising throughout the nation, and unoccupied spaces large enough to accommodate a parking structure are more difficult to find in most urban areas.
The parking industry has responded by increasing parking efficiency, increasing the number of structures built below ground (when financially feasible), introducing mechanical and/or robotic parking, and integrating the parking facilities with other uses such as housing, retail and transportation centers.
A current trend in the development and real estate industries is creation of mixed-use centers, where at least three revenue-producing uses are integrated functionally and physically. These mixed-use centers allow people to live, work and play in the same location, and they are pedestrian-friendly.
A mixed-use center’s generated parking demand can be calculated using principles of shared parking for such integrated uses. Parking demand can be reduced by up to 40% when compared with the parking demanded by each individual land use.
Mixed-use developments are becoming more common and are forcing cities to re-evaluate parking requirements. They also are allowing owners to build smaller structures where the majority of the parking stalls will be occupied throughout the day.
A small percentage of U.S. parking facilities are constructed of steel; most are built of pre-cast concrete or cast-in-place concrete. Because of increasing construction costs, parking garage owners have to be conscientious in choosing a method of construction that is reasonably priced, as well as relatively fast.
Pre-cast concrete usually will fulfill this requirement, unless the garage site is too far from the pre-cast plant, and transportation costs (especially with increased fuel costs) become an issue.
Also, the long-term maintenance costs can be higher for pre-cast concrete when compared with traditional cast-in-place concrete. It is estimated that the numbers of parking facilities built of either pre-cast or cast-in-place concrete are very similar.
Since concrete and steel reinforcement costs are on the rise, some owners and designers are looking to structural steel as a lower-cost alternative, sometimes saving as much as 25% in construction costs per parking space.
The United States has been slow to accept automated parking revenue control technology, compared with Europe and Asia. Traditional exit cashiering has been the norm until recently, and many new parking developments are still requiring that cashier booths be included in the design.
However, the entire parking industry is moving toward automation in the form of central cashiering / pay-on-foot technology. The labor costs and issues associated with traditional exit cashiering have compelled the change to implement pay-on-foot solutions. The public has accepted and embraced the “new” parking technology.
The future of the U.S. parking structure is the move to “green” or sustainable design practices, such as recycling materials, efficient power and water use, landscaped roofs, and additional convenience for bicycle users, car pools and hybrid vehicles. The facilities also will be integrated with other transportation methods as the need for alternative transportation becomes more accepted.
One thing is for sure – the “architecture” of U.S. parking structures will continue to adapt as do their users, construction materials and transportation modes.
Laura Barbero-Buffa, a Parking Consultant with Walter P. Moore, can be reached at firstname.lastname@example.org. Contact Robert A. Chapman, a Principal and Senior Parking Consultant with the firm, at email@example.com.
Article Abstract from May, 2008