Elevator Parking in Residential Buildings

November, 2007

– Is This a Trend?

The growth of high-rise condominiums in high-density urban areas continues to cause a parking dilemma in major cities throughout the U.S. Sites often are too small to accommodate ramps between floors. This has forced architects to design buildings with car elevators servicing flat-floor parking structures within them. For safety purposes, these vehicle elevators require valets to service the parking and retrieval of cars.
We have received a number of inquiries in recent months from design architects about the feasibility of using vehicle elevators to service flat-floor parking structures in residential projects across the country. The primary question they have asked is: “Will the number of vehicle elevators we propose be able to handle the traffic demands?”
This is an important issue considering the incredibly high expense that would be involved if the number of vehicle elevators that were initially built were unable to manage the traffic demand. Not only have architects inquired about the serviceability of the car elevators, owners also are also curious to know how many valets are required to handle the peak-hour traffic demand and have a fiduciary obligation to provide accurate information to the proposed condominium associations.
As we began investigating the issue, we quickly realized there were very little data to help simulate a valet parking elevator operation. This type of operation is unique because of its dependency on accurate traffic demand information. For example, if there are too many or too few valets working in a parking lot, an owner can easily adjust the number of valets. For a parking structure relying on vehicle elevators, if there are too many elevators or not enough elevators on-site, it isn’t cost-effective to eliminate one or create a new one.
That is why it is important for an owner and architect to determine prior to construction how many car elevators are needed to meet the traffic demand of the proposed building. A simple simulation methodology should be available to determine the capacity of a valet using a car elevator to park or retrieve cars, and we set out to develop such a process.
Methodology
The methodology in determining how many vehicle elevators and valets are needed must rely on data available in the concept stage of development, primarily preliminary building plans. These plans illustrate how many spaces are available, the characteristics of the parkers in the parking structure, elevations of floors, locations of parking levels, and the internal vehicular and pedestrian paths in the building. Other factors considered are available from equipment manufacturers and from surveys of human factors.
For this type of analysis, we analyze each step in the parking and retrieval process of cars. We break the valet operation into components, calculate a time/distance factor for each, and determine the operational capacity for each elevator and for each valet attendant. Each step takes a specific amount of time to complete, which was determined by a survey of a similar situation, from the manufacturer, or by analyzing the preliminary plans of the proposed building. Remember, of course, that these are the basic steps for parking and retrieving a car; however, they can always change based on the specific project.
In order to determine the capacity of a valet using a vehicle elevator, we divide the average parking time per vehicle into one hour. This gives the number of cars that a valet is able to park in any given hour. Multiplying that number by the number of elevators gives the total capacity in the peak hour. If the proposed design includes two vehicle elevators, but two vehicle elevators with two valets proves to be inadequate to handle the peak hour demand, then the analysis has to take into account the cycle process of three valets using two vehicle elevators.
Trip-Generation Analysis
In order to determine if the capacity of the proposed number of vehicle elevators is sufficient, it has to be compared with the peak-hour trip-generation demand of the proposed building. This means an analysis has to be conducted.
Once the number of cars generated during the peak periods for the proposed building has been determined, it is compared with the capacity of the vehicle elevators to see if an extra valet or even an extra car elevator is needed.
We have devised a method of analysis that takes into account any unusual circumstances, so that we can calculate an accurate estimate of the vehicle elevators’ capacity for a proposed building.
Design Implications
A capacity analysis of vehicle elevators can provide a huge saving to a project. It is able to determine how many valets are necessary to handle the building’s parking demand, which could prevent the hiring of too many valets. More important, it could determine if the number of vehicle elevators in the preliminary design is too many or too few. Either way, it could save the owner a lot of money.
It was discovered that a vehicle elevator capacity analysis is an essential step in the preliminary design phase of any building with a vehicle elevator serving flat-floor parking structures. And due to the increasing density of major cities, the potential value of building condominiums or apartments on any land available in cities, and the narrow design of these buildings, it has become more and more common to incorporate vehicle elevators.

Gerald Salzman is Senior Parking Planner at Desman Associates in Chicago. David Taxman is the firm’s Traffic & Parking Analyst/E.I.T.
They can be contacted via e-mail at gsalzman@desman.com and
dtaxman@desman.com.