Four Different ‘Ps’ – Proper Planning Provides Payoff

By Bill Arons

In 1998, the Wayne County Airport Authority embarked on a $1.2 billion terminal expansion project at Detroit Metropolitan Airport. The project included a new terminal (the McNamara Terminal), which would serve as Northwest Airlines’ Detroit hub, and a parking garage.
The garage was built with 11,500 spaces, some of which were taken out of service after Sept. 11, 2001. Currently, the garage has 10,900 spaces, including short-term, long-term, valet and employee parking areas. Of those, 10,070 are available to the public, along with 7,000 short-term, long-term and economy spaces in a garage and a surface lot at the North Terminal.
Walker Parking Consultants prepared the initial studies for the McNamara Terminal garage, and went back in 2007 to review subsequent growth and changes.
Establishing the Parking Facility Capacity
Two different analyses were done to determine the best size for the parking facility, and it turned out that the two approaches yielded similar results. One method was to review the airport’s parking revenue statistics and compare them with enplanement projections. Parking demand was related to “Detroit area” originating enplanements to arrive at a parking generation ratio that could be used to project out to the future. This approach identified a need for 11,000 to 12,000 stalls.
Coming at the problem from the other side, we determined the maximum number of parking spaces that could be provided within the available ground area and structure volume, as limited by FAA height regulations. The airport authority wanted to make the most of whatever space was going to be used for parking, so planning to the physical capacity of the site made sense. We determined that the capacity would be approximately 11,500 stalls.
Part of the challenge of planning the facility was determining the location of parking for different user groups. The design concept was to minimize the internal drive time plus the walking time for the majority of the parkers. Our study of user patterns in the parking system revealed that hourly parkers (“meeters and greeters”) and valet parkers generated 65 percent of the vehicles and 75 percent of the pedestrians.
Because of the great percentage of total volume of traffic, and because these cars didn’t stay long (average stay is less than three hours) but “turn” spaces frequently, parking nearest the pedestrian bridge to the terminals was earmarked for this user group. Daily parking was located farther from the pedestrian bridges, and economy parking was given the most remote sections of each level. Employee parking, too, was given a more remote location.
The garage was built with 10 parking levels at roughly 1,620’ x 240’ each, for a total floor area of 3.748 million square feet. All floors are flat. The garage contains one pedestrian connection to the terminal, and moving walkways on one level.
Following Up
At the time of the study in 1998, enplanements at the airport were 15.5 million. Northwest Airlines (NWA) accounted for 76% of this total (11.8 million). The NWA “local area” originations were 40% of its enplanements (4.72 million). NWA originating enplanements were projected to grow to 7.6 million by 2020, an increase of 61%. This information was utilized to project the future parking needs at the McNamara Terminal parking facility. (Actual growth far outpaced the projection, as shown in the nearby Sidebar.)
Further examination of data collected since our original study revealed the following patterns:
Long-term (LT) Parkers – Comprised 60% of all parkers, with an average “length of stay” over three days. LT “turnover” was a maximum of 0.80 (on a daily basis). LT parking areas filled to capacity two to three days of a normal week. [The increase in LT parkers as a percentage of the total is a result of building LT parking so close to the terminal. Parkers who might otherwise use off-airport parking are likely to use such convenient long-term parking .]
Short-term (ST) Parkers – Comprised 37% of all parkers, with an average “length of stay” at three to four hours. ST parker “turnover” was a maximum of 3.65 (on a daily basis). When our study began in 1998, ST parkers accounted for 65 percent of the cars. In part, the drop is a result of restricted access for “meeters and greeters.”
Valet Parkers – Comprised 3% of all parkers, with an average “length of stay” at two to three days. Valet parker “turnover” was a maximum of 0.70 (on a daily basis).
Parkers Per Originating Enplanement – The ratio of on-airport parker per enplanement, at this terminal, was approximately 0.20 (one parked vehicle for every five enplaning passengers). This was true in 1997 also.
Parkers Per Day – The busiest transaction day occurred in December, when 8,981 exit transactions were processed.
Revenue Outpaces Projections
With enplanements growing so much faster than anticipated, it came as no surprise during our review to find that revenues also had outpaced the 1998 projections.
Calendar year 2007 revenue was about $54.2 million (33% above the initial estimate), surpassing even the 2017 projection. Periodic rate changes played a role in this increase, along with the faster-than-expected enplanement growth. Revenue equated to $7.17 per originating enplanement. The high revenue month was March, with $5.189 million (9.6%).
Other Developments
New pay-on-foot machines went online in November 2007. This system, named “FastPay,” works with the “Credit Card In / Credit Card Out” option or with cash. Data from this system on four busy days in December 2007 indicate that about 35% of the parkers chose pay-on-foot.
During 2007, about 50% of all exit transactions were paid with credit cards, which accounted for 65% of the revenue.
The decision by the Wayne County Airport Authority to build the maximum number of parking spaces, and to build them next to the terminal, was wise. Since enplanements grew faster than expected, the garage filled sooner than planned; the airport was ready.
Patron acceptance is obvious since LT parking areas are full two to three days each week. The savings in time – the ability to park quickly, the short walk to the terminal – are things that travelers appreciate.
Annual parking revenues are much higher than originally projected (33% higher for 2007). This is due to increases in the daily maximum rates and increasing enplanements. This also is due to the significant increase in LT parkers – 60% of the total, with an average fee of $53.05 in 2007.
The ratio of on-airport parkers to originating enplanements has remained constant at 0.20 over the past 10 years.
Bill Arons, P.E., is a parking consultant with Walker Parking Consultants. He can be reached at

Article Abstract from April, 2009

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