Roberson St Lot by Flickr User Rubyji

In Sunday’s (3/24/2013) Chapel Hill News, the second left-hand editorial expressed concern over parking management for Shelton Station and the recent purchase of the Roberson Street lot by the town. The paper suggests that by buying parking in one part of downtown while considering ways to reduce the demand for parking at Shelton Station in another part of downtown, the Aldermen are acting at cross purposes by pursuing both initiatives.

Is Carrboro Talking Out of Both Sides of Its Mouth on Parking?

This editorial lacks context in a few places, and it is worth unpacking them one at a time.

Carrboro’s thoughtful development has made it one of the Triangle’s most livable and entertaining towns.

But the town can’t have it both ways.

Let’s start here.  The town is not having anything “both ways.” As the piece goes on, it seems to portray the issue as if asking Shelton Station’s developers to reduce the amount of proposed parking to be NEWLY BUILT onsite is somehow a REDUCTION in parking downtown while the Town purchasing parking that ALREADY EXISTS and is being used today is an EXPANSION of parking. To clear things up, Shelton Station will definitely add some amount of parking to downtown; how much has yet to be determined.  The purchase of the Roberson St lot does not add a single parking space to downtown.  It moves the control of the property’s destiny from the private sector to the public sector.

Is Shelton Station Significantly Out of Step with Town Parking Requirements, and Is That a Problem?  Or an Opportunity?

The editorial goes on:

As proposed, Shelton Station would have 170 parking spaces – fewer than the town requires.

This is partially true- the town has base-level requirements for various uses, and within certain parts of town, mostly close to downtown, developers can take reductions in parking based on the assumptions that some uses will share parking.  The developers have arrived at the 170 spaces listed above by accurately applying the shared parking reduction formulas of the town to the base parking requirements.

However, this only matters if the parking requirements make any sense, and in the United States, generally, they don’t. What’s wrong with parking requirements, particularly those from the Institute for Transportation Engineers (ITE), which the Town of Carrboro uses? Fortunately, Donald Shoup, the pre-eminent expert on parking in the US, and perhaps the world, has done the heavy lifting for us.

From Shoup’s landmark paper, “The Trouble With Minimum Parking Requirements”:

Where do minimum parking requirements come from? No one knows. The “bible” of land use planning, F. Stuart Chapin’s Urban Land Use Planning, does not mention parking requirements in any of its four editions.1 The leading textbooks on urban transportation planning also do not mention parking requirements. This silence suggests that planning academics have not seriously considered or even noticed the topic. This academic neglect has not prevented practicing planners from setting parking requirements for every conceivable land use. Fig. 1 shows a small selection of the myriad land uses for which planners have set specific parking requirements.

Without training or research, urban planners know exactly how many parking spaces to require for bingo parlors, junkyards, pet cemeteries, rifle ranges, slaughterhouses, and every other land use. Richard Willson (1996) surveyed planning directors in 144 cities to learn how they set parking requirements. The two most frequently cited methods were “survey nearby cities” and “consult Institute of Transportation Engineers (ITE) handbooks”. Both strategies cause serious problems.

Shoup goes on to point out that the “survey other cities” approach often leads to the repetition of mistakes of other communities.  Carrboro is particularly susceptible to making this type of mistake because very few towns Carrboro’s size possess a level of transit service or cycling usage anything like ours.

Carrboro does, however, use on the handbooks of the Institute of Transportation Engineers in its analysis of how much parking certain uses require in town.  All of the italicized quote below is Shoup’s commentary except for the section in blue, which is a direct quote from the ITE Parking Generation manual:

To base parking requirements on more objective data, planners consult Parking Generation, published by the Institute of Transportation Engineers. For each land use, this publication reports the “parking generation rate”, defined as the peak parking occupancy observed in surveys by transportation engineers.

A vast majority of the data… is derived from suburban developments with little or no significant transit ridership… The ideal site for obtaining reliable parking generation data would… contain ample, convenient parking facilities for the exclusive use of the traffic generated by the site… The objective of the survey is to count the number of vehicles parked at the time of peak parking demand (Institute of Transportation Engineers, 1987a, vii±xv, bold added by Shoup).

The ITE summarizes the survey results and reports the average peak parking occupancy observed at each land use as the parking generation rate for that land use. Half of the 101 reported parking generation rates are based on four or fewer surveys of parking occupancy, and 22% of the parking generation rates are based on a single survey. Because parking is free for 99% of all automobile trips in the United States, parking must be free at most of the ITE survey sites. Parking generation rates therefore typically measure the peak demand for parking observed in a few surveys conducted at suburban sites that o€versample free parking and lack public transit. Urban planners who use these parking generation rates to set minimum parking requirements are making a big mistake.

So what does a page out of the ITE Parking Generation handbook look like? Anybody familiar with statistics and regression analysis who has not seen ITE parking math before is in for a treat. Check out this scatterplot- click to enlarge:

This is a recommended equation for calculating parking for a fast food restaurant in the ITE Parking Generation Manual, based on the thousands of square feet of leasable space in a restaurant.  It has a R-squared value of 0.038. Put another way, the ITE gives urban planners a chart and equation to forecast the peak demand for parking at a certain type of restaurant in which they admit that over 96% of the variables that explain variation in peak parking demand are not captured by the chart or the equation. I’m ignoring the fact that they have 18 observations and that my grad school faculty said never to conduct regression analysis with less than 30 data points.

The bottom line is that with these equations and 3-decimal point numbers, the ITE manuals look like highly scientific documents, when in fact they are at best alchemy conjured to replicate conditions for single-use buildings that contain all their parking on one site, in places where that is a wise strategy because land is not terribly valuable.  They contain a value judgment that everyday parking should be sized to meet peak demand, which is the philosophy that brings us massive fields of parking for Thanksgiving Day shoppers that sit mostly empty 315+ days per year outside big box stores. These types of analyses were never meant to work in downtowns, and even as a first step prior to shared parking reductions like that which has been contemplated in the Shelton Station application, we should put limited stock in them.

Anyone seeking an informative and entertaining read on the folly of minimum parking requirements should read Dr. Shoup’s entire paper here (PDF 324k). It’s not a long read and there are many graphics. The first 7 pages lay out most of the problems quite well.

Returning to the Chapel Hill News editorial, the piece concludes:

The aldermen may be right to relax the parking requirements for Shelton Station. But if they’re wrong those cars are going to have to park somewhere. Before the project comes back, they may want to figure out just how much parking downtown really needs.

This is not necessarily true.  Those cars might not have to park somewhere.  What the CH News staff is missing here is that downtown attracts PEOPLE first, and also, as a secondary derived consequence of attracting PEOPLE, also attracts VEHICLES, which include:

• BIKES
• BUSES
• FOOTWEAR
• SCOOTERS
• WAGONS
• STROLLERS
• and yes, CARS

Travel behavior surveys from around the country and the UNC campus show that most people, when living in a community that provides transportation choices, use several different modes in any given week.  You might drive to work but walk to the Farmers’ Market on Saturdays.  You might take the bus to UNC for work but drive to the movies with friends.  (you might consider taking the bus home from the movies if it ran later, too)

The key point is that people are reasonably smart and if they want to come to downtown Carrboro, and we give them choices, and encourage them to make choices that keep the downtown less congested and allow more access for others to do the same, then many of them will figure out other ways to get downtown than get in a car.  This already happens thousands of times a day, every day- in downtown Carrboro. Some of them will still drive, and that’s fine as long as we don’t do things that makes downtown less vibrant to ensure they have a perpetual supply of free spaces.

If We Shouldn’t Trust ITE Manuals or Other Communities’ Unscientific Standards, How Should We Evaluate What the “Right” Amount of Parking is for Development, Particularly Downtown?

First, we should realize that there is no bureau of Parking Weights and Measures coming to sue us/yell at us/etc if we make unorthodox choices.  We’re on our own, and that’s good.

Second, we should discuss parking policy through the prism of our goals. Vision 2020 aims to double commercial space downtown.  Space for parking competes directly with that goal, which is why we need to focus on providing ACCESS to downtown rather than parking.  I wrote a column on Orangepolitics on this subject five years ago that I think still applies well today. Access will require improving our environmentally friendly mode access to downtown, and probably involves eventually putting a market price on parking downtown.

Third, we should conduct research on how people get to businesses in downtown Carrboro. What the exact percentage is, I’m not sure- but the percentage of people arriving at Weaver Street Market to shop on foot, by bike, and by bus is surely very, very, different than your standard grocery store.

Fourth, we need to recognize that the fragmented parking landscape of downtown with many owners, all trying to reserve parking for their own customers, contributes to congestion and air pollution when people drive from lot A across the street to lot B to avoid triggering a towing policy, even though the individual moving their car across the street is the mutual customer of two downtown businesses.

When Dan Burden visited in 2001, he recommended that we figure out how to get more shared parking arrangements in downtown.  With the exception of Fitch Lumber allowing Weaver Street Market customers to park there for Thursday night and Sunday morning events, I don’t think this has really happened in any tangible way in downtown.

Back to Shelton Station

This last point is where unbundling parking comes in, and remains a key variable for Shelton Station. Technology has improved a lot over the last ten years and may offer us an opportunity to create “virtually shared” parking in town.  If Shelton Station is approved with the 170 spaces that the shared parking portions of the Town parking rules allow, or even some lower number of spaces, then if there is a carsharing vehicle onsite, renting apartments with unbundled parking will maximize the chance of the Shelton Station lot having capacity because lower-car ownership households will have an incentive to rent there that is not present elsewhere in town.

If after unbundling, Shelton Station developers find they have seven empty spaces pretty much all the time, then it would be great if they could put those seven spaces into a “shared parking pool” for downtown.  We could call the system, you guessed it — “CarrPark.”

These spaces would have a special sign letting people know that while most of the Shelton Station property was reserved for residents and businesses on site, that these seven spaces could be used by anyone WILLING TO PAY the market rate for that parking space at that time of day and day of the week.  Surely at some times of the week, that price would likely be zero, but at others, there would be a per-hour charge that would be adjusted by time of day to make sure that Shelton Station’s shared spaces were priced to be 85% full and 15% empty all the time.

Why would any developer do this?  Easy- they could keep any revenue from the spaces after the costs of registering those seven spaces in the CarrPark system were accounted for. Over time, a network of CarrPark parking spaces would be created downtown, on both public and private lots.  The town could put its public lots into the CarrPark system and build the computerized backend, which would include sensors that share real-time information on whether or not a parking space is empty. Visitors to downtown could check a real-time information app before they drove into town to see which lots had the most availability, and what their price per hour is.

This approach would allow incremental changes, one parking space at a time, to yield genuinely shared parking in downtown Carrboro across multiple public and private lots, without necessitating complicated land swaps among parking space owners.

While an electronic shared parking “CarrPark” system is obviously a longer-term idea to discuss for the community, the key point for projects like Shelton Station which will reach the Aldermen’s table soon is this — there are a lot of parking innovation tools we could deploy to make downtown Carrboro even more lovely for pedestrians while making it a lot more convenient to park downtown.

All of them are likely to work better if Shelton Station rents apartments and parking spaces to residents separately in an Unbundled fashion.

The other stuff can come later; but this is a great time to try Unbundling. I hope we can see this happen through a condition in the use permit for the site, or some other appropriate mechanism the town can come up with.