How to Do a Parking Study
About Designing Local Parking Surveys
We believe any discussion of parking needs should start with a survey of existing parking use. Whether your concern is parking in the town center or how much parking to require of a new development, you need to know have much parking is currently available and how is it used. Both public and private parking spaces should usually be part of any survey, and any set of solutions. Many simple counts can be accomplished by community staff or local volunteers with minimal training. The guidance below is intended primarily for community staff and local volunteers in designing and carrying out your own survey, or for community staff reviewing proposed data collection proposals as part of the special permit process.
The Need for a Survey
Area versus Site-Specific Surveys
Local parking surveys are usually designed to answer one of two questions:
- Is there enough parking nearby?
- How much parking should be required for a new development?
Area Parking Surveys
Area parking surveys are intended to consider all the parking available in an area, whether it's the downtown or a neighborhood commercial center. They are usually conducted in response to a perceived lack of parking, now or in the near future, and having a sound knowledge of current conditions is a good basis for deliberations about how to respond.
Besides identifying who is parking and how long, area surveys can also identify where there are unused spaces nearby that could be shared, for specific purposes and targeted parkers. For example, church parking could be used for overflow parking for the few peak shopping days of the year, rather than building to peak parking needs which will remain empty (and not generating profits and taxes) for most of the year.
An area survey will also give you an indication of how well your local zoning requirements are matching supply of parking with demand.
Parking requirements in many zoning ordinances frequently result in many empty spaces and extra costs for the developer. The traditional way to determine parking requirements is through the use of parking ratios developed nationally by the Institute for Transportation Engineers  and surveys of existing regulations across the country from the American Planning Association . These have been developed for hundreds of different uses based on surveys of existing buildings and areas and are based on anticipated square feet or acres of development or the number of employees that might work there. They are easy to use and legally defensible, but they almost always lead to more parking than is needed for most days. These are generally collected at suburban locations poorly served by transit and are designed to encourage auto use.
We believe locally developed standards, based on surveys, better serve local needs. If you don't have the time or resources for a survey, at least use these correction factors developed by the Victoria Transport Policy Institute based on studies from around the US and Canada that allow you to customize your requirements based on your local situation (see flexible parking requirements for more information). 
Parking Requirement Adjustment Factors
A better way is to collect use data from comparable, local examples. Usually special permit regulation can require a survey be done before the requirements are set. The community sets the survey method, picks the location(s) survey, and reviews the results. Find a site in your community or in comparable communities in eastern Massachusetts that has a similar land use and a comparable size, if possible. In a location with comparable access - near transit, close enough to residences of the community center so that walking can occur, near to a highway exit ramp, etc. MAPC can help identify comparable sites to survey.
Counting vehicles parked at a comparable site or sites can better tailor parking demand to local conditions, and also factors in New England weather and our propensity to drive, for example.
Parking minimums and special permit surveys allow developers to demonstrate that their use will not need the normally required number of spaces. Parking maximums and special permit surveys allow developers to demonstrate they need more. Setting all parking requirements through the special permit process allows the community to decide on the parking needs for a specific use at a specific site. Any of these approaches provides a flexibility that provides for much more efficient use of land than a simple adherence to strict parking standards.
There is a potential future problem with this survey approach however. If a site is redeveloped in the future, a potential new use may legitimately require more parking spaces than were built to match the current needs. Rather than having a redevelopment parcel lie empty waiting for just the right match between new use and available parking, contingencies like landscaped parking reserves or fees-in-lieu can be built in now to allow for the future expansion of parking supply.
Survey Stakeholders First
Before beginning any survey you should interview local stakeholders to learn about perceived parking needs and problems. Try to get the local stakeholders involved in the survey and in the search for solutions. Is overcrowding a problem for only a few blocks or is there a mismatch between supply and demand covering a large area? What times of the day do the problems occur, and is this weekdays only or are weekends involved? How you design your survey will depend on the answers to these questions.
The survey includes an inventory of spaces, counts of vehicles parked, and an analysis of the results. In total the survey should give you a clear picture of how existing parking is being used in the area surveyed. How the demand for parking might change in the future is a different type of analysis, and we'll give you some ideas about how to go about doing that in the last section below.
These basic survey procedures apply whether you are surveyed a central business district or just an individual lot to determine future parking requirements. If you are surveying a single private parking lot you should certainly explain your purpose before counting there. For an area survey, widespread publicity is not recommended so as not to influence the outcome, but notification of the local police and operators of enclosed, gated lots is necessary.
Inventory existing parking
- Define the study area (talk to stakeholders) - at least a few blocks beyond the area if spillover parking is a concern. The outer edge of the study area should be defined by the maximum distance someone would park and walk who has business near the center of the area. The larger your study area the more volunteers you will need to help with a count.
- Number the blocks. Number the block faces and all the individual parking areas (public and private) within a block. Put this information on a good map before you start counting spaces and vehicles parked. For all private parking you should also find out who owners the property, or at least the entity that is currently leasing the spaces for use.
- Count the number of spaces, on-street and off, for each of the numbered parking areas. If spaces aren't marked, take the maximum number of vehicles you found parked, and estimate how many additional vehicles could be parked without blocking other vehicles, fire lanes, trash receptacles, etc. You can use the chart below to estimate on-street parking (do not count driveways in the measured distance). As you are counting, note any restrictions on the use of these spaces.
- Are they private parking spaces, restricted to employees and customers (who)? Handicapped plates only? Loading zones or trucks only?
- Are there limitations on how long or what hours of the day the spaces may be used?
- Where a fee is charged, what are the rates?
This information can all be recorded as you are counting the numbers of vehicles parked, but if that count will cover many block and parking areas in a limited amount of time it is probably best to prepare this inventory before you begin counting cars. You should include bicycle parking racks, rings, and all types of equipment specifically designed for bicycle use in this inventory.
The chart is from "Parking Management Made Easy: A guide to taming the downtown parking beast. Transportation and Growth Management (TGM) Program, a joint program of the Oregon Department of Transportation (ODOT) and the Oregon Department of Land Conservation and Development (DLCD).
Inventory all parking spaces - record or estimate number of parking spaces, owner, who is allowed to park, cost, and any time restrictions. For any area, include all spaces within ½ mile of the target area.
Count the number of parked vehicles
- This can be a simple count of the number of vehicles parked in each of the numbered parking areas. You should survey at least 3 or 4 different time periods during the day, including all times with peak demand. You may also need to count on Saturday or Sunday, depending of the weekend demand.
- One or more persons can do these counts, depending on the size of the area to be covered. A good map with the number of spaces available at each location should be marked, and a walking route to follow should be designated if more than one person is involved in the counting. Besides counting the numbers of cars parked legally, double parked vehicles, or those blocking other vehicles in lots should also be indicated, and any large trucks blocking more than one space should be recorded. Make sure you count the number of bicycles parked as well, even if they are not attached to a piece of bike parking equipment.
- Make sure to count only on days when the weather is good. If you count in winter make sure there is no accumulated snow blocking parking spaces that would normally be available.
- Counting how long vehicles remained parked provides more useful information for parking management solutions, but requires more work. Knowing the duration of parking allows for different parking pricing or time restriction policies, may uncover opportunities for sharing spaces, and can provide helpful information to businesses looking to move to an area.
Duration counts require that license plate numbers be marked, and that counters return frequently (at least once an hour) to a space to record this information. For high parking turnover locations (post offices, banks, convenience stores, etc.) you may want to check back every 15 minutes. This is usually best accomplished by numbering all spaces on the map, and by providing both maps and numbered sheets with room to record the license plate numbers. Again, record both legally and illegally parked vehicles.
After the survey is completed, by matching licenses plates you can determine how long vehicles remain parked at the same spot (you may also be able to use license plate matching to notice if some people are moving their cars between nearby spaces). To measure parking duration there is no need to match license plates with vehicle ownership records, and all the recorded license plate information can be destroyed as soon as the duration analysis is completed. Be sure to emphasize to anyone concerned that not of the information collected will be used for enforcement of parking regulations.
Land Use Information
Besides counts of the numbers of vehicles parking, you need information on the land use that the parking is serving. If you are counting a single use on a single lot, the size of the lot in acres, the number of usable square feet in the building, and the type of use of the building are all necessary pieces of information. Where there are multiple companies and uses of a building the approximate square footage used by each should be estimated. Types of uses and usable square feet should be measured in the same way that your local ordinance defines them. The number of employees working in the building at the time of the survey will also be extremely helpful if you can get it. If you are surveying an area the local assessor's office is probably the best source of use and square footage. Involving building owners and the local business community in the survey is probably the best way to both insure accurate information and their involvement later in the search for solutions.
Analyzing the Results
Two measures of parking use typically result from these studies. Counting cars parked allows you to calculated occupancy, the measure of how many of the available spaces are occupied. Vehicles parked divided by the number of spaces is occupancy. Occupancies of 85-90% are usually considered full, since someone looking for a space will not find an empty one easily and may need to circle as few times before one becomes available. Occupancies above 100% are possible, when vehicles park in the aisles, or block other vehicles. Occupancies should be calculated separately for every parking area you identified, and for each time period you counted.
Duration is the length of time a car remains in a space, and can be estimated from the license plate information, if collected. Calculate the duration for each vehicle observed, and then calculate an average duration for all spaces by parking area and time period. Report average durations in 15 minute intervals for averages under 1 hour, in hourly increments over one hour.
Turnover is the inverse of duration, and allows you to calculate how many cars can use a space in a given period of time. For example, for an average duration of 15 minutes, 4 different vehicles parked there in an hour. If the turnover/duration remained unchanged, 32 different vehicles could be accommodated in that one space over an 8 hour period.
Keep all these results separate, at least initially, by location, time of day and day of week. Graphics and displays on maps will be helpful in explaining your results.
Knowing occupancy allows you to determine whether or not you have enough parking. Occupancies of 85-90% or just below are ideal - the demand is being met without waste. High occupancies in one area combined with lower occupancies nearby indicate a parking management problem - you need to figure out how to get some of the excess demand to use the nearby available supply (lack of knowledge of nearby spaces or restrictions on who can park there are two examples why demand and supply don't match up.
Knowledge of duration allows you understand the parking market better (the need for short-term versus long-term parking, for example) to redefine time restrictions and parking fees and to use existing spaces more efficiently. Duration information should reveal if there are different parking markets in different areas, and different time periods.
Occupancy and duration information shows if overflow parking to residential neighborhoods is an issue, and when. And the maps you prepare can ultimately be used to publicize parking locations and underutilized spaces.
1. Todd Litman, Evaluating parking Management Benefits. 2006. VTPI.
2. Institute of Transportation Engineers, Parking Generation, 3rd Edition, 2004. Available for purchase from the ITE website: http://www.ite.org/tripgen/parking.asp.
3. Michael Davidson & Fay Dolnik, Parking Standards (PAS 510/511), APA Planning Advisory Service, 2002. Available for purchase from http://www.planning.org/APAStore/Search/Default.aspx?p=2423.