As urban areas continue to grow and the demand for efficient land use increases, the need for structured parking solutions has become more critical than ever. When surface lots no longer meet the parking demands of a building, commercial center, or service hub, the development of structured parking becomes a viable—if costly—solution.
Understanding the Need
Parking is often an underestimated consumer of both land and resources. In many developments, such as shopping centers, parking space requirements can be as high as 1.5 square feet for every square foot of leasable space. For office buildings, this ratio typically stands at around 1 square foot per leasable square foot.
While surface parking is a less expensive option, costing significantly less than structured parking (sometimes up to five times cheaper), it is not always the most efficient or sustainable use of land—especially in high-density urban environments. In such cases, building upward with parking structures allows for higher development density and more strategic land use, potentially freeing up surface areas for other infrastructure or green space.
Planning for Parking Space
One of the first and most important steps in planning a parking structure is accurately determining how much parking is genuinely needed. This includes assessing:
- Parking Generation: The number of vehicles expected to be parked based on the current land use.
- Parking Demand: The actual number of parking spaces needed, including allowances for peak hours, special events, or other high-traffic scenarios.
Parking demand is influenced by a variety of local factors including development density, public transportation availability, regional policies, economic conditions, and parking costs. Typically, planning begins with a national standard based on a 100% automobile modal split, which is then adjusted for local context.
Key Issues in Parking Demand
Planning effective parking structures involves navigating several critical issues:
1. Units of Measurement
Parking requirements are generally expressed as a ratio, such as “X spaces per Y square feet” of building area. However, discrepancies can arise depending on how building area is calculated:
- Net Floor Area (NFA): Interior usable area.
- Gross Floor Area (GFA): Total building footprint, including walls.
- Gross Leasable Area (GLA): The portion of the GFA that is leased to tenants, often used in multi-tenant buildings.
These variations affect how parking requirements are calculated and must be standardized during the planning process.
2. Design Day and Hour
Planners must identify an appropriate “design day” and “design hour” to base parking needs on realistic usage patterns. It is inefficient to build a parking structure that can only accommodate vehicles during the peak of peak demand, as this results in excessive vacancy at other times. Instead, designers use regression curves and historical data to find a balanced solution.
3. Effective Supply
Real-world inefficiencies such as misparked cars, snow accumulation, or vehicle maneuvering must be accounted for. This is known as the effective supply cushion—extra space built into the design to accommodate unexpected challenges. Thus, Parking Demand = Parking Generation + Effective Supply Cushion.
4. Accessory Uses
Some spaces within a property do not directly generate traffic (e.g., utility rooms, storage areas) but are essential to operations. The role of these accessory uses should be carefully evaluated to avoid over- or under-estimating parking requirements.
5. Complementary Uses
Mixed-use developments often include businesses or services that operate at different hours or serve different functions (e.g., an office complex with a ground-floor café). These uses may have overlapping parking needs or offer opportunities for shared parking, which can reduce the overall required space. Local zoning laws and regulations must be considered when planning parking for such developments.
Toward Smarter Parking Infrastructure
Modern parking planning is not just about accommodating cars—it’s about using land more wisely, integrating transportation systems, and reducing environmental impact. By investing in parking structures rather than expansive surface lots, cities can support denser development, promote walkability, and make better use of valuable urban space.