Parking Structures
What Transportation Engineers Mean by Parking Structures
Parking structures—also called parking garages, decks, or podiums—are multi-level facilities designed to store vehicles efficiently while protecting people and the surrounding transportation network. In transportation engineering, a garage is not just a building; it is a system where demand (how many spaces are needed, when, and by whom) meets geometry (aisle widths, stall angles, ramp types), structure (spans, framing, durability), and operations (access control, revenue collection, maintenance).
Readers typically want answers to: How many spaces should we build? Which layout fits our site? What are typical slopes, widths, and clearances? Which structural system is most economical? How do we add EV charging, wayfinding, and license-plate recognition? How do we design for safety, accessibility, and future conversion (e.g., to offices or last-mile logistics)? This guide distills the essentials for feasibility studies, concept design, and upgrades to existing garages.
Did you know?
Optimizing the parking layout can increase capacity by 5–12% without adding floors—just by refining stall angles, end-bay design, and ramp placement.
Goal: deliver the fewest safe, durable, and user-friendly spaces needed—no more, no less—while enabling mode shift and future adaptation.
Demand, Utilization & Right-Sizing
Begin with purpose: employee parking, hospital visitors, mixed-use retail, university, or transit-oriented development. Each has different arrival peaks, turnover, and lengths of stay. Right-sizing aligns supply with peak-hour occupied spaces while accounting for shared use, policy targets (e.g., demand management), and future trends (rideshare, micro-mobility, EVs).
Peak Occupancy (Back-of-Envelope)
- Shared parking: Mix uses with offset peaks (office + evening retail) to lower total supply.
- Policy levers: Price to keep 5–10% vacancy at the peak; unpriced demand tends to overfill.
- EV readiness: Roughly 10–20% EV-capable conduits day-one; expand with demand.
Quick Check
Survey actual demand for a week, including special events. Peak 15-minute counts are more useful than daily totals for sizing entry gates and ramps.
Layouts, Angles & Efficient Geometry
Layout choices drive capacity and user experience. Common patterns include two-way 90° parking, one-way angled (60°/45°), and helix or split-level arrangements. Key parameters are stall width/length, aisle width, module depth, column spacing, and turning paths.
- Stall width: 2.6–2.75 m typical for public facilities; add 0.15–0.25 m at columns.
- Aisle width: 6.0–6.7 m for 90° two-way; 4.9–5.8 m for 60° one-way.
- Clear height: 2.1–2.3 m min public; 2.4–2.7 m for vans/EV chargers where required.
- End bays: Widen or chamfer to improve maneuvering and reduce curb strikes.
Spaces per 1000 m² (Rule-of-Thumb)
Important
Align columns with stall dividers, not stall centers, to avoid door conflicts and to simplify drainage slopes.
Structural Systems & Materials
Parking structures are repetitive-span buildings where durability is paramount. Common systems are precast concrete (double tees), cast-in-place post-tensioned slabs, and steel with composite decks. Selection depends on span length, speed of erection, seismic/wind demands, and lifecycle cost.
- Precast: Fast erection, long spans (15–18 m), clean soffits; pay attention to joint watertightness and diaphragms.
- CIP Post-Tensioned: Excellent watertightness and continuity; flexible geometry for tight sites.
- Steel/composite: Lightweight; good where foundations are limited; requires robust corrosion protection.
Durability Must-Haves
Low-permeability concrete, corrosion inhibitors, hot-dip galvanized steel, drainage to trench drains, and traffic-bearing waterproofing at ramps and joints.
Circulation, Ramps & Access Control
Circulation should be obvious at first glance. Keep entry/exit points visible from the street, avoid conflicts with sidewalks and bike lanes, and provide stacking space so queues don’t spill back into traffic. Inside, choose between one-way up & down ramps, two-way ramps, or external helices to free floor plates.
- Ramp slopes: 6–8% comfortable; up to 12% short stretches; landings every 12–15 m for two-way ramps.
- Gate placement: Place readers/ticketing 6–9 m upstream of the barrier to fit one vehicle clear zone.
- Wayfinding: Overhead arrows, color-coded levels, and dynamic space counters reduce circulation time.
Ramp Capacity (Approx.)
Safety, Fire Protection & Security
Engineering for safety begins at the curb and continues to the stair door. Provide generous sight triangles, pedestrian priority at entries, and lighting levels that feel safe without glare. Address fire risks with passive fire separation, sprinkler coverage where required, and dedicated smoke/heat ventilation strategies (natural or mechanical).
- Lighting: 75–100 lux at drive aisles; uniformity matters more than maximums; use vandal-resistant luminaires.
- Pedestrian routes: Protected walkways, clear crossings, and direct access to elevators/stairs.
- Security: CPTED principles—open sightlines, camera coverage, and active ground floors where possible.
Important
Separate vehicular and pedestrian decisions: never force pedestrians to walk behind gate arms or across ramp throats without a refuge island and marked crosswalk.
Smart Parking Technology & Revenue Systems
Modern garages use PARCS (parking access and revenue control systems) with license-plate recognition (LPR), barcode/QR, proximity cards, or mobile credentials. Space-by-space sensors or camera analytics feed wayfinding signs and mobile apps. Dynamic pricing manages peak loads, while EV chargers add electrical and billing complexity.
- Frictionless entry: LPR + account on file eliminates tickets and speeds entry/exit.
- Counting: Loop detectors or vision-based counting per level & zone for accurate availability.
- Data: Export APIs to TDM dashboards to track utilization, dwell time, and revenue per space.
Daily Revenue (Simple)
Did you know?
Zone-level guidance signs often yield 8–15% faster space finding compared to only entry counters—less cruising means lower emissions and happier users.
Accessibility, User Groups & Special Stalls
Design for everyone: drivers, pedestrians, cyclists, delivery vans, and emergency vehicles. Provide required accessible stalls with compliant routes from stall to destination, stroller-friendly gradients, and safe curb-free paths. In mixed-use garages, separate public, residential, and service areas with clear access control.
- Accessible stalls: Near elevators, with access aisles and headroom suitable for vans.
- Short-term/Click-and-Collect: Signed pick-up zones near exits; keep dwell short to avoid blocking.
- Bicycle parking: Secure rooms or cages at grade; visibility boosts usage.
Sustainability, Resilience & Future Conversion
The greenest space is the one you don’t build. Pair right-sizing with shared parking and pricing. For the spaces you do build, reduce embodied carbon (cement substitutes, optimized reinforcement), design for deconstruction, and plan for future adaptive reuse by providing flat floor plates where feasible and higher ground-floor clear heights.
- Energy: LED lighting with occupancy/daylight sensors; photovoltaic canopies on top decks.
- Stormwater: Capture/pretreat deck runoff; avoid pollutant discharge to waterways.
- Heat island: High-albedo surfaces and planted facades where fire and maintenance allow.
Consideration
Future conversion works best with long spans, flat plates, 3.5–4.0 m clear heights, and cores placed to support non-parking uses later.
Cost, Delivery & Risk
Costs vary widely by market and system, but major components include substructure/foundations, structure, waterproofing, facades/screens, MEP, PARCS/IT, elevators, lighting, and fire systems. Delivery options: design–bid–build, design–build, or public-private partnership with availability or revenue-risk structures. Early contractor involvement helps with precast lead times and crane logistics.
- Phasing: Maintain adjacent site access; temporary surface lots can bridge during construction.
- Utilities: Provide spare conduits for future EV chargers and camera drops; separate life-safety power.
- Quality: Mock-ups for joints, coatings, and deck waterproofing reduce rework and leakage claims.
Operations & Maintenance
A garage is a 24/7 asset. Plan for routine inspections (decks, joints, drains), winter operations (de-icing chemicals and wash-downs), and revenue audits. Create a maintenance matrix with frequencies for cleaning, sealing, re-striping, joint replacement, and equipment calibration.
- Water is the enemy: Keep drains clear; slope decks (1–2%) to trenches; fix ponding immediately.
- Coatings: Traffic coatings at ramps and high-turn areas extend life; re-top per manufacturer intervals.
- Data hygiene: Validate LPR/credential lists; reconcile transient vs. monthly parker revenue.
Lifecycle Cost (Sketch)
Parking Structures: Frequently Asked Questions
How many spaces should we build?
Measure actual peak demand, consider shared parking, and apply pricing to keep 5–10% vacancy. Use contingency sparingly; oversupply is expensive and discourages transit use.
What’s the most efficient layout?
One-way 60° stalls with one-way aisles are intuitive and compact; 90° two-way can be efficient with long spans. Choose based on site width, turning paths, and desired circulation.
Which structural system is best?
Precast for speed and long spans; post-tensioned for watertight continuous slabs on tight sites; steel/composite where weight or erection constraints dominate.
How do we integrate EV charging?
Provide EV-capable conduits and panel capacity day-one, start with 10–20% equipped stalls, and expand with demand using load management to avoid service upgrades.
How do we design for future conversion?
Prefer flat plates, higher clear heights, and column grids that suit office/residential. Place cores and ramps to be removable or repurposed later.
Conclusion
Parking structures succeed when they balance capacity, safety, durability, and long-term flexibility. Start by right-sizing supply, then pick a layout and structural system that fits the site and supports clear, low-stress circulation. Engineer details that matter—joint waterproofing, drainage slopes, lighting, and wayfinding—because they define user experience and lifecycle cost.
With modern access technology, dynamic pricing, and EV readiness, garages can operate efficiently today while remaining adaptable for tomorrow. Integrate sustainability through material choices, energy-smart lighting, and strategies that enable future conversion. The result is a resilient mobility asset that supports the wider transportation system—not just a place to store cars.
Design fewer but better spaces, make them easy to use, and plan for a future where mobility keeps evolving.