Parking surveys have traditionally been conducted to address parking supply/demand, utilization, and turnover issues as part of the transportation planning process. However, as travel demand models have become increasingly sophisticated, parking surveys are also being used to provide additional travel behavior data for input into the modeling process. For example, parking generation surveys can improve the travel model calibration process by identifying and matching the demand and supply of vehicle trips generated to and from parking facilities located within specific traffic analysis zones (TAZs). Parking pricing surveys can also provide a more sophisticated understanding of the price elasticities of parking costs that greatly affect mode choice and consequently, travel behavior.
Parking surveys conducted to improve the travel modeling process are similar to workplace or establishment surveys, in that trip-makers are usually surveyed at the attraction end of their trip. The purpose of collecting these data relates to the number, type, and geographical distribution of the trips attracted to a specific facility within the framework of the travel model. Workplace and establishment surveys are more common, and, in many cases, may prove to be more effective in gathering travel behavior data than parking surveys. An important consideration related to the implementation of parking surveys is that, by definition, the data may be biased since only information about the automobile travel mode is collected.
Survey teams should consider using the parking survey instead of the workplace and establishment survey (or as a supplement to either) for input into the travel modeling process:
- To obtain data about specific parking facility (lots and garages) locations;
- To obtain accurate parking facility cost data;
- To obtain trip origin and destination data on automobile users who may park in a central location while traveling to their actual destinations by other modes such as walking and public transportation (e.g., shoppers and workers in a Central Business District);
- To obtain auto, transit, and walk access information for trip makers traveling from parking facilities to their actual destinations;
- To obtain information on the short-term and long-term parking facility mix;
- To obtain detailed information for specific subareas within the travel modeling system; and
- To obtain data on trip making to and from park-and-ride facilities if new infrastructure improvements are being considered.
- A special consideration is “parking congestion”, an analog to roadway congestion. Data on when parking lots reach capacity and how that alters travel behavior is an important component of any fine-grained facility analysis.
The following types of parking facilities should be targeted for surveying in order to collect travel behavior information for input into the travel modeling process:
- Parking garages or lots available to the general public. If a facility serves only one employer or one building, a workplace/establishment survey will likely result in a higher response rate at lower survey implementation costs. Also, if a particular parking facility is only open to specific parkers such as parkers with monthly passes, parking surveys will probably not be an effective means of gathering unbiased travel behavior data.
- Parking garages or lots available to the general public that cater to non-work users such as shoppers and tourists. These types of activities are less predictable than work travel, and therefore parking surveys may provide additional input and detail about overall travel behavior.