11,492 Spaces


11,492 Spaces

Detroit Metropolitan Wayne County Airport is nearing completion of a $1.2 billion expansion project, which has as its centerpiece, a new 97-gate McNamara Terminal that will serve domestic and international flights for the airport’s major air carrier, Northwest Airlines, its partners and signatory international carriers.
The project includes a fourth parallel runway, a roadway from the existing airport to the new terminal, a three-level roadway structure adjacent to the terminal, upgrading of the existing terminals, utility improvements and an 11,492-space parking structure.
Northwest Airlines served as the design and construction manager for the terminal project and was instrumental in the selection of all A/E consultants for all projects. Walker Parking Consultants was the prime design firm for the team that provided design services for the parking structure.
The total number of spaces to serve the airport patrons will be about 32,000 — 62 percent on-airport and 38 percent off-airport.
This structure is the largest public parking structure ever constructed in one phase. Exactly 11,492 parking spaces are provided on 10 parking levels with a total floor area of 3.9 million square feet (89 acres). The typical parking level is 1620-by-240 feet, although most levels are not typical due to site constraints.
Precast and prestressed concrete was used for all columns, beams and pretopped tee floor units. Double-threaded circular helices (96-feet O.D.) are provided at the north and south ends of the structure to provide for vertical automobile circulation, both up and down. These helices provide flexibility to vary the parking supply for the five user groups.
Parker types
The parking structure is designed to accommodate five user groups: Hourly Parkers (less than three hours), Daily Parkers (one to three days), Valet Parkers (three hours to three days), Economy Parkers (more than three days) and Other (employee).
So where does one locate these user groups within a 10-story structure that has one pedestrian connection to the terminal (Level 6) and where the roadway access is provided at Levels 2 and 4? Wayne County provided data for 1997, noting the percent of transactions for each of the user groups, which was utilized to develop a space allocation plan. (See sidebars.)
The user group locations were selected to balance internal driving time, internal walking distance, parking duration characteristics and the parking fee per hour or day.
Parking rates at most airports have evolved over time in relation to local patron acceptance, to rates in the off-airport parking lots and to the revenue needs of the airport. Parking revenue is a significant component of the total revenue generated at an airport.
In the 1997 study it was found that the percent of revenue generated in the various areas on-airport was as follows:
* Short term: 25 percent.
* Long term: 55 percent.
* Economy: 20 percent.
The gross parking revenue generated at the airport in 1997 was approximately $37 million and had increased to almost $49 million by 2001.
Because there are distinct parking areas with pricing differentials, the internal automobile circulation system was then designed to make it easy for the drivers and to maintain the necessary separation. Automobile access into the parking structure is provided from the lowest terminal roadway (international arrivals) and from the upper terminal roadway (departures). The middle roadway (domestic arrivals) does allow commercial vehicles to enter a two-story area on Level 4 of the structure for drop-off and pick-up functions.
All circulation elements, entry areas and exit areas within this massive parking structure have been located and sized to handle the automobile traffic volumes which will be associated with enplanements in the year 2020. This is also true of all pedestrian circulation elements: 13 elevators, five escalators and three moving walkways.
Revenue control
Factors considered in the technical evaluation process were experience on similar projects, proposed management plan, approach and schedule, and DBE involvement. The costs from the vendors were considered after the ranking was completed via the technical evaluation. Components of the system include:

* 18 entry lanes with mag-stripe ticket dispensers.
* 18 exit lanes (12 with cashier booths, six with exit validators)
* 10 pay-on-foot machines in the lobby on Level 6.
* Three cashier stations on Level 6.
* Card reader access at all entry/exit areas.
* Four control gates at most of the helix/floor intersections.
* Pass-through gates on many of the floors.
* Fiber-optic wiring for the entire system.
* A valet parking control system.
* An automobile occupancy count system, which will display stall availability.
* A complete hardware/software package for revenue control.
* The ability to utilize a 100 percent online LPI system in the future.
* More than 60 electronic signs, some with variable messages.

The revenue control contract was won by Federal APD (out of four invited to bid) for a price of about $2.8 million including the booths. There is no license plate inventory at this time but it is designed for a future LPI expansion.
A key element of this revenue control system will be patron acceptance of the pay-on-foot concept at DTW. All pedestrian traffic must pass through the enclosed lobby on Level 6 upon returning from the terminal. The 10 pay stations are located within the lobby with space provided for more pay stations in the future. It is the consultant’s opinion that 40 to 50 percent of the parking patrons will utilize the pay-on-foot stations in year one, with usage increasing to 75 to 90 percent by year five. Patron acceptance of this system will minimize cashiering requirements.
Project summary
The intent of the design process was to develop the optimum patron wayfinding system for both the driver and the pedestrian. Design was accomplished with an understanding of the pedestrian and vehicle volumes associated with each of the user groups. Flat parking floors were recommended from the start.
This massive parking structure provides nearly 11,500 parking spaces on 10 floors. The locations of the five user groups have been selected to make the parking experience user friendly for “most of the people, most of the time”.
A major design decision was to create a double-threaded circular helix at the two ends of the facility to provide for up-and-down automobile flow between the flat floors. This internal flow system is optimum for patron wayfinding since all parking spaces are on the flat floors, which do have four color-coded sections. A detailed car counting system, capable of directing drivers to the floors with available spaces, is a byproduct of this choice. Finally, the decision was made to develop a parking operation incorporating pay-on-foot stations to reduce operating expenses and to reduce patron queuing at exiting.

William Arons, PE, is a senior vice president with Walker Parking Consultants, designer for the Detroit Airport Project.

Sidebar 1:
Airport Parking Supply (approximate)

On-airport parking structure No. 1
6,187 spaces

On-airport parking lots
2,400 spaces (approx.)

Midfield Terminal Parking Structure
11,492 spaces

Off-airport private parking lots
12,000 spaces (approx.)

Parking Rates
Rates at the new parking structure at Detroit Metropolitan Wayne County Airport:

Short Term
First hour $5
Second hour $2
24 hours $25

Per day $26

Long Term
First hour $4
Second hour $1
24 hours $13

Per day $8

Sidebar 3:
User Groups
At Detroit Metropolitan Wayne County Airport, hourly parkers comprise about 62 percent of the vehicular traffic. To minimize the elevator needs within the facility and to provide a high degree of convenience, the hourly parking spaces are near the pedestrian bridge connection to the terminal. Escalators are provided between Levels 6 and 7. Hourly parkers will have a high parking fee to discourage overnight parking.
Valet parkers comprise about 2 percent of the vehicular traffic. The drop-off/pick-up area is located adjacent to the lobby to optimze patron service.
The daily parkers comprise about 24 percent of the vehicular traffic. These vehicles have an occupancy, on average, of one person and account for business travel. They are located on seven of the 10 levels within a reasonable walking distance of the elevator core closest to the pedestrian bridge location.
The economy parkers comprise about 12 percent of the vehicular traffic. Nearly one third of all parking spaces (30.6%) in the facility are for this group, and are located on all 10 levels of the structure. Parking in these spaces calls for the longest drive inside of the structure and the longest walk to the moving walkways and pedestrian bridge.

Article contributed by:
William Arons, P.E.
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