14-5353

Parking in Urban Centers: Policies, Supplies and Implications in Six Cities

Submitted to Transportation Research Board

Submission date: November 15, 2013

Words: 5,935 Tables and figures: 6 Total word count: 7,435

AUTHORS

Christopher McCahill* Research Assistant, University of Connecticut Department of Civil and Environmental Engineering 261 Glenbrook Rd., Unit 3037 Storrs, CT 06269-3037 Phone: 872-216-6703 Email: [email protected] Jessica Haerter-Ratchford Research Assistant, University of Connecticut Department of Civil and Environmental Engineering 261 Glenbrook Rd., Unit 3037 Storrs, CT 06269-3037 Phone: 860-486-0586 Email: [email protected] Norman Garrick Associate Professor, University of Connecticut Department of Civil and Environmental Engineering 261 Glenbrook Rd., Unit 3037 Storrs, CT 06269-3037 Phone: 860-486-2990 Email: [email protected] Carol Atkinson-Palombo Assistant Professor, Department of Geography University of Connecticut 215 Glenbrook Road, Unit 4148 Storrs, CT 06269-2037 Phone: 860-486-3023 Email: [email protected] * Corresponding author

TRB 2014 Annual Meeting Paper revised from original submittal.

Parking in Urban Centers: Policies, Supplies and Implications in Six Cities ABSTRACT A majority of American cities specify minimum parking requirements in local zoning codes, even in areas served by a variety of travel options. Little work has been done to understand how aggregate parking supplies compare to requirements in urban areas or to evaluate the potential impacts of meeting parking requirements in these places. This research tracks changes in parking supplies and the built environment in six urban business districts between 1960 and 2000. It also offers a summary of parking requirements in each city and compares those requirements to actual supplies.

This research demonstrates that parking requirements can only be met through a combination of costly parking infrastructure and considerable commitments of land. In half of the cities studied – those with more stringent parking requirements – off-street parking supply ratios increased by 150 to 300 percent, requiring comparable amounts of land, but still fell short of area-wide parking requirements. By quantifying existing parking supplies in urban areas and evaluating the potential impacts of increasing those supplies, this work offers guidance and justification for establishing parking standards that conform to long-term transportation and development goals.


McCahill, Haerter-Ratchford, Garrick and Atkinson-Palombo 1

Parking in Urban Centers: Policies, Supplies and Implications in Six Cities 1 2 INTRODUCTION 3 A majority of American cities specify minimum parking requirements in local zoning 4 codes to ensure that parking needs are fully accommodated on-site for all new 5 construction. Requirements are often based loosely on estimates of parking demand 6 published by the Institute of Transportation Engineers (ITE) and by surveying the 7 requirements of similar or nearby cities. Parking demand estimates commonly assume 8 that nearly all trips will be made by automobile and may not be appropriate in dense 9 urban areas that offer a variety of travel options. In these cases, some cities reduce their 10 requirements or offer exemptions. However, little work has been done to understand how 11 aggregate parking supplies compare to requirements, how parking requirements have 12 affected dense urban areas, or to evaluate the potential impact of parking requirements 13 associated with new construction in these places. 14

This research tracks changes in parking supplies and the built environment in six 15 central business districts between 1960 and 2000. It also offers a summary of parking 16 requirements in each city and compares those requirements to actual supplies. This study 17 demonstrates that parking requirements can only be met through costly parking 18 infrastructure, considerable commitments of land, or a combination of the two. Given 19 these challenges and consequences, parking requirements have the potential to inhibit 20 future development, further fragment the urban environment and undermine efforts to 21 manage travel demand. This work offers guidance and justification for establishing 22 parking standards that conform to long-term transportation and development goals. 23 24 BACKGROUND 25 The rapid growth in popularity of the personal automobile following its introduction to 26 the United States market in 1896 (1) posed problems for American cities (2). Increases in 27 urban automobile ownership and use between 1930 and 1950 led many to believe that 28 existing parking facilities were inadequate (3). To address these concerns, transportation 29 professionals proposed parking ordinances that prescribed a certain amount of off-street 30 parking for new construction projects or changes in land use. For roughly half a century, 31 the concept of minimum parking requirements has informed parking standards in most 32 cities around the nation, contributing to a rapid growth in parking supplies. In recent 33 decades, however, some cities have begun instituting parking management policies with 34 the intent of curbing some of that growth in parking. 35 36 Minimum Parking Requirements 37 Minimum parking requirements are commonly put in place to ensure that there are 38 sufficient parking supplies to meet current and projected demand. This approach dates 39 back to the 1920s, when parking policies were added to a growing list of zoning 40 regulations in many cities including regulations on building height, building area and 41 building use (3). Between 1950 and 1970, these requirements became common policy in 42 almost every major city around the nation (4). Parking requirements and evolving design 43 practices were all part of efforts to allow the efficient, unencumbered movement of 44 automobiles. 45



In 1952, the Eno Foundation published a report documenting the positive 1 implications of off-street parking requirements, recommended parking policies and 2 compiled metrics used in many cities to meet current and projected parking demand (3). 3 Since then, factors such as rising incomes, long-term mortgages, veterans’ assistance, 4 periods of low fuel prices, construction of the interstate highway system, new growth in 5 automobile-oriented suburbs and the reconfiguration of older urban places have all 6 contributed to rising levels of automobile ownership and use, consequently increasing 7 pressures on urban transportation systems (2). In response, parking regulations became 8 widespread – along with standards guiding street geometry, sidewalk widths, acceptable 9 levels of traffic flow and traffic control – in order to impose order and increase efficiency 10 of vehicle traffic flow (2, 5). By the 1970s, more than 95 percent of large American 11 cities included parking requirements in their zoning codes (4). 12

The second edition of Parking Generation (6), published by ITE in 1987, was the 13 first widely distributed national dataset on parking demand (4). Successive editions were 14 published in 2004 and 2010. Parking Generation offers guidance on typical parking 15 demand for various land uses. A fourth edition of Parking Generation (7) contains 16 parking ratios for 106 land uses. A majority of the data was collected at suburban sites, 17 with little to no public transportation service and ample free parking. 18

Although the ITE data are intended to be used as a reference point, giving the user 19 an idea of the general nature of parking demand for a given land use, the parking demand 20 rates listed in Parking Generation are often treated as baseline values for municipal 21 parking requirements. Unfortunately, these estimates are often applied without 22 accounting for many of the factors that influence parking demand such as proximity to 23 activities, demographics, land use patterns, and travel options (7–9). The application of 24 peak demand rates developed in suburban locations to set parking requirements in urban 25 areas has contributed to major changes in the form and function of those settings (10). 26 27 Parking Management 28 While most cities still have established minimum parking requirements, a growing 29 number of American cities have implemented policies to limit and manage parking 30 supplies (11). The shift was motivated in large part by a growing recognition that a one-31 size-fits-all approach to off-street parking can be harmful to urban vitality and other local 32 objectives (9, 10, 12, 13). Rather than prioritizing parking provision, parking 33 management strategies strive to achieve optimal supplies of parking and make efficient 34 use of existing supplies. 35

Parking management represents a fundamental change in how parking issues are 36 perceived, compared to the conventional approach of setting minimum parking 37 requirements, and it requires balancing a wider range of policy goals (14–16). These 38 goals often focus on economic development, urban regeneration, social equity, 39 environmental impacts and the optimization of transportation infrastructure. Strategies 40 include maximum parking allowances, shared parking provisions, parking pricing, 41 financial incentives for developers and property owners, flexible requirements, improved 42 transit service, walking and cycling improvements and land banking (9, 11). As with the 43 minimum parking requirements, the management of parking is typically enforced through 44 the municipal zoning code or similar types of ordinances. 45 46



Parking in Urban Areas 1 As prior research has shown, parking demand in urban areas depends on a variety of 2 factors. A study of residential parking at 206 sites in King County, Washington, revealed 3 that parking utilization varies from nearly zero to more than 1.5 spaces per dwelling unit 4 depending on key factors such as transit access, walking access, concentration of people 5 and jobs, block size and the supply and price of parking (8). A number of recent studies 6 have shown that both parking supplies and parking use per 1,000 ft2 of building space are 7 considerably lower at urban sites and mixed-use center than at suburban locations (17, 8 18). Despite this variation, research also suggests that minimum requirements 9 consistently exceed demand by a substantial margin. Even when parking supplies fall 10 short of stated minimum requirements, they are commonly between 50 to 80 percent 11 occupied (17–19). 12

As this finding suggests, parking requirements that do not fully account for shared 13 parking among buildings or trips made by modes other than automobile do not reflect the 14 realities of parking use in many urban areas. Perhaps more importantly, parking policies 15 that focus solely on perceived demand fail to account for the tangible and intangible costs 16 associated with supplying abundant parking in urban areas (10, 12, 13, 20). Among the 17 most substantial impacts are the large-scale loss of land and the physical transformation 18 of urban places (12, 21). Urban parking polices must strike a balance between providing 19 sufficient parking and mitigating the harmful impacts associated with oversupply. 20

Unfortunately, few studies offer valuable estimates of overall parking use or take 21 into account the physical impacts of parking supplies in urban areas. This study helps 22 bridge this gap in knowledge by assessing current parking requirements as well as 23 changes in the overall parking supplies and in the built urban form for six urban centers 24 over a period of 40 years – offering a valuable perspective on the implications of parking 25 requirements for future development and the potential to reform parking policies in urban 26 places. 27 28 METHODOLOGY 29 The six cities examined in this study are: 1) Arlington, Virginia; 2) Berkeley, California; 30 3) Cambridge, Massachusetts; 4) Hartford, Connecticut; 5) Lowell, Massachusetts; and 6) 31 New Haven, Connecticut. These cities were chosen from a database of more than 100 32 cities to cover a representative range in terms of current levels of automobile use and 33 changes in automobile use between 1960 and 2000. Each city had a population of around 34 100- to 150-thousand people in 1960 and experienced no more than 25% change in 35 population during the study period, which ensures that it was largely built-up before 1960 36 and later adapted to changes in automobile use. 37

The boundaries of measurement for this study include the central business district 38 in each city. Boundary definitions were based largely on analysis of aerial photographs 39 taken during the 1950s. Each study area includes the most heavily built-up core of 40 development during that time and is adjusted to conform to current census tracts 41 definitions. These study areas represent the central locations for vital development and 42 activity in each city and allow us to characterize changes in the built environment over 43 time. In Cambridge, this includes the area surrounding Harvard Square. In Arlington, 44 this includes the Orange Line corridor from Ballston to Rosslyn. In Berkeley, this 45 includes the Shattuck Avenue corridor and South Side neighborhood. The study areas – 46



depicted in Haerter-Ratchford (22) – range from 11,000 ft2 in Lowell to 60,000 ft2 in 1 Arlington. 2

This study relies on two key data sources: 1) a review of current parking policies, 3 and 2) geographic data pertaining to parking provision and the built environment between 4 1960 and 2000. These data sources and the procedures used to compile data are outlined 5 below. Additional data regarding rates of automobile use for each city were acquired 6 from U.S. Census journey-to-work tables. 7 8 Parking Policies 9 A variety of parking demand estimates and parking requirements – including ITE’s 10 Parking Generation (7) and municipal zoning codes – are assessed and summarized in 11 this study in order to cross-compare with estimates of parking supplies for each study 12 area. Parking Generation reports 85th percentile parking demand estimates for various 13 land uses during weekdays and weekends. The weekly range of estimates for selected 14 land uses are summarized below. 15

Given the complexity of some city’s zoning codes, each was reviewed 16 systematically to determine a typical range of parking requirements for each study area, a 17 full-range of citywide parking requirements and a description of typical exemptions and 18 allowable reductions. These summaries represent the most recent available version of 19 existing zoning codes. Some assumptions (outlined in Table 1) are made based on 20 language from zoning codes to convert all units to spaces per 1,000 ft2. 21 22 Urban Fabric Infrastructure: Buildings and Parking 23 Considerable changes in the urban fabric over the last several decades were partly related 24 to the characteristics of the buildings, including their height, area and location. To 25 quantify these changes, these attributes were measured in geographic information 26 systems (GIS) using aerial imagery taken near the beginning and the end of the study 27 period. Buildings were identified as any enclosed structure used to support urban 28 activities. Google Earth, Google Maps and Bing Maps were consulted to determine the 29 number of levels in each building for the 2000-2010 aerials. Identifiable parking 30 structures were not included in estimates of useable building space. 31

The high quality of data eased the measurement process for the most recent data 32 set. However, the measurement process for earlier time periods posed some difficulty. 33 Due to lower resolution imagery, the measurement of heights for the earlier time periods 34 required additional steps to ensure validity. A visual survey of the present data overlaid 35 on the historic aerials identified buildings standing over the entirety of the study period. 36 These buildings with known heights were used as reference points for the measurement 37 of building characteristics in earlier time periods. Other surrounding clues such as 38 shadows and neighborhood characteristics helped to estimate the heights of buildings in 39 the 1950s. 40

Parking supplies were also estimated from aerial photographs for each time period 41 according to procedures detailed by McCahill and Garrick (23). Estimates include 42 surface parking lots, parking garages and on-street parking, but do not include small 43 private driveways, underground facilities and parking incorporated into buildings. The 44 number of parking spaces in surface lots and parking garage spaces was determined by 45 dividing the total area by 350 ft2 (32.5 m2) – the average area for each space taking travel 46



lanes and area for maneuvering into account, estimated from analysis of more than 100 1 individual lots. The number of on-street parking spaces in each city was estimated by 2 dividing the total length of curb dedicated to parking by 20 feet per space. Total areas for 3 on-street parking were estimated by multiplying curb length by 7 feet – the approximate 4 width of a parked car, rather than the marked area. 5

From the GIS data, researchers determined the total floor area for parking and 6 useable space, along with the total footprint for each. These values were used to estimate 7 parking ratios for each study area (treating each area as a system), the average building 8 heights, the portions of land devoted to parking or buildings and other measures 9 characterizing the built environment, which are outlined below. The researchers used 10 linear interpolation between years with available imagery to estimate values in 1960 and 11 2000. 12 13 RESULTS 14 15 Parking Policies 16 Table 1 shows a summary of typical parking requirements for selected land uses in each 17 city. The full ranges of parking minimums for various zones throughout each city are 18 shown in brackets and any maximum parking allowances are shown in parentheses. 19

Recommended values from Eno and ITE increased somewhat for most land use 20 types between 1952 and 2010. However, other than for dining and assembly uses, these 21 increases were not substantial. Ferguson (4) attributes this to the fact that early parking 22 requirements were set quite high, perhaps in anticipation of future demand. 23

Baseline parking requirements generally do not vary considerably among the 24 cities in this study. Some notable exceptions include the following: 25

26 - Higher than average requirements for multi-family dwellings in Hartford and 27

Lowell; 28 - Higher than average requirements for office uses in Lowell; 29 - Higher than average requirements for retail uses in New Haven; and 30 - Higher than average requirements for assembly in Arlington and New Haven. 31 32

After taking parking exemptions and reductions into account, the cities exhibit a 33 considerably wider range in terms of allowed and required parking. Arlington and 34 Berkeley offer exemptions and reductions, respectively, near major transit facilities. 35 Cambridge and New Haven offer large reductions within key central business districts. 36 Berkeley, Cambridge and Hartford allow reductions in conjunction with travel demand 37 management plans. Lowell allows parking requirements to be met through the leasing of 38 existing public spaces, rather than the construction of new spaces. Finally, Cambridge 39 imposes maximum parking allowances for most land use types, which are actually equal 40 to or lower than minimum requirements in some other cities. Other exemptions and 41 reductions are included in Table 1. 42

Other than for multi-unit dwelling, there are few instances in which the parking 43 requirements for any given city meet the 85th percentile estimates of parking demand 44 from ITE. In a majority of the cases, typical parking requirements are on the order of 45 one-half or less of ITE estimates. These requirements are even lower after exemptions 46



and reductions are accounted for. In the case of Cambridge, typical maximum parking 1 allowances are lower than parking generation estimates from ITE. 2 3 TABLE 1 Typical Parking Requirements (spaces per 1,000 ft2) 4

Multi-unit dwellinga Office Retail Assembly Dining Industry

Eno 1952 1.0 1.0 - 5.0 1.0 - 5.0 5.0 - 10 2.0 - 6.6 0.4 - 1.0 ITE 2010b 1.1 - 1.9 2.9 - 3.5 2.4 - 5.9 14 6.4 - 21 1.2 Arlington 1.0 - 1.1 1.0 - 1.7c 1.0 - 1.7 15d 3.3e 1.0 [1.0 - 1.5] [1.0 - 3.5]c [0.0 - 1.9] [15]d [3.3]e [1.0] Berkeley 0.3 - 1.0 2.0 2.0 2.0 3.3 1.0 [0.0 - 1.0] [2.0] [0.0 - 2.0] [2.0] [3.3] [1.0] Cambridge 1.0 1.0 - 1.3 1.1 - 2.0 3.3 - 10d 1.3 - 4.0e 0.5 - 0.8 [0.5 - 1.0] [1.0 - 1.3] [1.1 - 2.0] [3.3 - 10]d [1.3 - 4.0]e [0.5 - 0.8] n.a. (2.0 - 2.5) (1.7 - 4.0) (5.0 - 20)d (2.0 - 8.0)e n.a. Hartford 1.0 - 1.5 1.0 1.7 0.3 5.0d 0.6f

[0.5 - 1.5] [1.0] [1.7] [0.3] [5.0]d [0.6]f Lowell 1.0 - 2.0 2.5 1.1 - 2.0 1.7 2.0 - 10 0.6 - 0.8 New Haven 1.0 1.7 5.0 12.5d 5.0e 1.0f

Exemptions and Reductions Arlington Requirements waived within 1,000 feet of transit for select uses (e.g., small

restaurants, small retail, grocery); 10% reduction for office and retail within 500 feet of transit.

Berkeley Reductions in some zones within 1/3 mile of transit or with travel demand management strategy; reductions for joint-use parking.

Cambridge Exemptions for schools with residences; exemptions through Zoning Board of Appeals; exemptions in Harvard Square overlay district

Hartford Reductions for joint-use parking (public assembly); up to 30% reductions with travel demand management plan.

Lowell Reductions for joint-use parking by time of day; parking may be leased from public facilities within 1,500 feet; reductions for residential parking near public facilities.

New Haven Reductions near car-sharing facilities; exemptions in business districts for select uses (e.g., assembly, small retail, ground-level office); maximum of 3 spaces per 1,000 ft2 for non-residential uses in business district.

a. For residential uses, assumed 1 dwelling unit = 1000 ft2 (per Berkeley ordinance) 5 b. 85th percentile depending on day of week 6 c. Average requirement for an assumed four-story building 7 d. For public assembly, assumed 1 seat = 20 ft2 (per Cambridge and Lowell ordinances) 8 e. For dining uses, assumed 1 seat = 50 ft2 (per Hartford ordinance) 9 f. For industrial uses, assumed 1 worker = 500 ft2 (per Arlington ordinance) 10 n.a. = not applicable 11 [ ] = full range of minimum requirements 12 ( ) = maximum parking allowance 13 Note: 1,000 ft2 = 92.9 m2 14 15



TABLE 2 Measures of Off-Street Parking and Built Environment 1 Off-Street Parking Spaces Building Area (1,000 ft2) 1960 2000 Change 1960 2000 Change Arlington 9,131 12,120 33% 18,964 51,956 174% Berkeley 4,162 3,882 -7% 13,450 15,653 16% Cambridge 1,888 2,622 39% 19,859 28,985 46% Hartford 10,134 39,586 291% 36,517 46,224 27% Lowell 2,896 7,302 152% 8,705 8,749 1% New Haven 3,065 19,680 542% 20,596 32,710 59%

Off-Street Parking Supply Ratio (spaces / 1,000 ft2 of building area)

Portion of Resident Commuters Driving to Worka

1960 2000 Change 1960 2000 Change Arlington 0.48 0.23 -52% 0.67 0.69 3% Berkeley 0.31 0.25 -20% 0.68 0.57 -17% Cambridge 0.10 0.09 -5% 0.42 0.43 1% Hartford 0.28 0.86 209% 0.53 0.74 39% Lowell 0.33 0.83 151% 0.70 0.91 28% New Haven 0.15 0.60 304% 0.58 0.73 26%

Portion of Land for Off-Street Parking Portion of Land for Buildings

1960 2000 Change 1960 2000 Change Arlington 0.05 0.07 29% 0.12 0.16 36% Berkeley 0.07 0.06 -17% 0.27 0.29 10% Cambridge 0.02 0.03 39% 0.20 0.27 31% Hartford 0.07 0.18 153% 0.23 0.20 -13% Lowell 0.09 0.17 88% 0.33 0.21 -35% New Haven 0.04 0.16 296% 0.32 0.30 -6%

Off-Street Parking Intensity (spaces / 1,000 ft2 of parking footprint)

Building Intensity (useable area / building footprint)

1960 2000 Change 1960 2000 Change Arlington 2.90 2.99 3% 2.63 5.31 102% Berkeley 2.86 3.22 13% 2.31 2.46 6% Cambridge 2.86 2.86 0% 3.24 3.61 12% Hartford 2.86 4.41 54% 3.19 4.66 46% Lowell 2.86 3.84 34% 2.37 3.65 54% New Haven 2.86 4.63 62% 2.52 4.26 69% a. From U.S. Census Bureau journey-to-work tables

2 3 4



TABLE 3 Measures of Parking Including On-Street Supplies 1

Total Parking Spaces

Portion of Spaces On-Street

Parking Supply Ratio (spaces / 1,000 ft2 of building area)

1960 2000 1960 2000 1960 2000 Arlington 24,690 28,713

0.63 0.58

1.30 0.55

Berkeley 12,938 12,807

0.68 0.70

0.96 0.82 Cambridge 10,731 13,351

0.82 0.80

0.54 0.46

Hartford 17,834 50,561

0.43 0.22

0.49 1.09 Lowell 5,030 9,350

0.42 0.22

0.58 1.07

New Haven 9,953 25,671 0.69 0.23 0.48 0.78 2 Parking Ratios and Built Environment 3 The results of the parking and built environment analysis are shown in Table 2, including 4 estimates of key measures such as parking ratios. As the data show, parking supply ratios 5 increased considerably in three cities (Hartford, Lowell and New Haven) and decreased 6 in three cities (Arlington, Berkeley and Cambridge). These changes are attributable in 7 large part to substantial increases in the total number of parking spaces in the former 8 three cities. However, parking ratios were also influenced by substantial changes in total 9 building area – most notably in Arlington, but also in New Haven and Cambridge. 10 Measures such as the portion of land devoted to parking or buildings and the intensity of 11 each describe key features of the built environment, as discussed in the following section. 12

Estimates of on-street parking supplies are included in a separate analysis, shown 13 in Table 3. On-street parking accounts for less than one-quarter of total parking supplies 14 in Hartford, Lowell and New Haven, signaling a marked decline in the role of on-street 15 parking in these places since 1960. On-street parking has consistently accounted for 16 more than 50 percent of supplies in Arlington, Berkeley and Cambridge, with a high of 17 80 percent in Cambridge. While on-street parking typically does not count towards 18 satisfying local parking requirements, its inclusion increases parking supply ratios 19 considerably. 20 21 THE REALITIES OF PARKING RATIOS 22 Off-street parking supply ratios vary considerably among different cities, from a low 23 value of 0.09 in Cambridge to a high of 0.86 in Hartford. While these estimates do not 24 include small private driveways that may be used for parking or parking that is concealed 25 under other structures, they offer valuable insight regarding typical parking supply ratios 26 in city centers, differences among the cities and changes over time. In some cases, the 27 inclusion of off-street parking in these estimates more than doubles the overall parking 28 supply ratios. With on-street parking included, parking supply ratios range from 0.46 to 29 1.09 in Cambridge and Hartford, respectively. 30

Even after accounting for this additional capacity from on-street parking, none of 31 the cities supply the required amount of parking within the study areas. Rough baseline 32 estimates of typical parking requirements in each city were calculated as the weighted 33 average of requirements for multi-unit dwellings (30%), office (50%) and retail (20%). 34 These calculations are shown in Table 4. Hartford provides approximately 90 percent of 35



the minimum required parking, while New Haven provides less than 40 percent. This 1 points to a considerable mismatch between the expectations laid out in local regulations 2 and the reality of how these places function – particularly when noting that typical 3 parking regulations do not take into account the contributions of on-street parking. It also 4 suggests that these requirements will continue to drive parking ratios higher as 5 development continues, which could potentially lead to unintended consequences, as 6 outlined in the section that follows. 7 8 TABLE 4 Typical Baseline Parking Requirements Compared to Actual Supplies 9 Typical Requirement (Average) Weighted

average requirementa Supplied

Multi-unit dwelling Office Retail

Arlington 1.1 1.4 1.4 1.3 44% Berkeley 0.7 2.0 2.0 1.6 51% Cambridge 1.0 1.2 1.6 1.2 39% Hartford 1.3 1.0 1.7 1.2 90% Lowell 1.5 2.5 1.6 2.0 53% New Haven 1.0 1.7 5.0 2.2 37%

a. Weighted average requirement = 0.3 Multi-unit dwelling + 0.5 Office + 0.2 Retail 10 11 12 IMPLICATIONS OF URBAN PARKING REQUIREMENTS 13 As shown above, parking supply ratios rose considerably in some cities, yet still fall short 14 of parking requirements. If parking requirements are expected to serve their intended 15 function, they will continue to push parking supplies up on a project-by-project basis. 16 The following analyses demonstrate the potential impacts of rising parking supply ratios 17 with regards to built form. These analyses highlight the potential unintended 18 consequences and associated costs of satisfying parking requirements. 19

Parking ratios are a mathematical expression of the relationship between 20 transportation infrastructure and the built urban environment. Parking requirements 21 mandate that a prescribed amount of space be set aside for storing vehicles along with 22 each new building. Given that the average off-street parking space requires roughly 350 23 ft2 (32.2 m2), a parking ratio of 3.0 spaces per 1,000 ft2 ensures that the amount of space 24 for storing vehicles will exceed actual building space. Parking ratios below this threshold 25 still have important implications for how urban space is configured, as the data in this 26 study illustrate. Parking ratios can be expressed in terms of their mathematical 27 relationship to measures of the built environment as follows: 28 29 𝑃𝑅 = !!!!

!!!! (1) 30

31 where 32 33

PR = parking spaces per useable building area (1,000 ft2) in a given study area, 34 XP = portion of land used for parking, 35 IP = parking intensity (parking spaces / parking footprint), 36 XB = portion of land used for buildings, and 37



IB = building intensity (useable area / building footprint). 1 2

Equation 1 illustrates specific changes in land use patterns that must occur as 3 parking ratios increase in urban areas. One option for increasing parking ratios is to 4 increase the total number of parking spaces – represented by the numerator in Equation 1. 5 This can be achieved through an increase in the amount of land used for parking (XP) or 6 by increasing the number of parking spaces that can fit on that land (IP). The latter is 7 typically achieved through the construction of multi-level parking structures or by relying 8 more heavily on-street parking. Parking ratios can also be increased by lowering the 9 amount of useable building space – represented by the denominator in Equation 1. This 10 typically occurs when part or all of a building is replaced by parking to meet more 11 stringent parking requirements associated with new construction. A doubling in parking 12 ratios could therefore be achieved through a doubling in the land use for parking, a 13 doubling in parking intensity on that land, a 50 percent decrease in useable building 14 space, or at minimum, a nearly one-quarter change in all three. Three different scenarios 15 and the implications of each are summarized by Willson (19), assuming no changes in 16 building intensity. 17

In reality, higher parking ratios are achieved through various combinations of the 18 factors described above. Data from the six cities in this study are used to explain how 19 different cities are configured to achieve their current off-street parking supplies and to 20 predict how they would be likely to increase those supplies. 21 22 Parking and Building Intensities 23 In order for parking supply ratios to increase without devoting more land to parking, 24 parking intensity must increase at a greater rate than building intensities – put simply, 25 parking structures must be made taller, relative to buildings. 26

Data from the six cities in this study (Table 2) show that this is rarely the case. 27 Moreover, when parking intensities have increased more than building intensities, it is 28 only by a small margin. In Berkeley, parking intensity increased by 13 percent compared 29 to 6 percent for buildings. In Hartford, the difference was 54 percent compared to 46 30 percent, respectively. In all other cases, increases in building intensity were far greater, 31 due mainly to increasing building heights. 32

On-street parking can also help to achieve higher parking intensities – typically 33 more than seven spaces per 1,000 ft2 (93 m2). For example, taking on-street parking into 34 account, the overall parking intensity in Cambridge is greater than seven. However, on-35 street parking provision has not changed considerably in any city since 1960 and 36 opportunities to add capacity are somewhat limited. 37 38 Land Use 39 In cases where parking intensity did not increase relative to changes in building intensity, 40 as described above, increases in parking ratios must be reflected in the amount of land 41 devoted to parking. Data from the six cities in this study (Table 2) show that the three 42 cities in which parking ratios increased devoted 88 to 296 percent more land to off-street 43 parking in 2000 than in 1960 and devoted less land to buildings. Cities in which parking 44 ratios decreased also devoted more land to parking (except for Berkeley), but this was 45 offset by more land also being used for buildings. 46



The above findings suggest that increases in parking ratios are most commonly 1 associated with a greater commitment of land to parking, rather than that land being used 2 more intensively. This represents a large value for XP in the numerator of Equation 1. 3 Data from Marshall and Garrick (17) is included here to validate this finding for parking 4 ratios higher than those represented in this study, as shown in Figure 1. These data show 5 reveal that town centers with parking ratios above 2.0 devote between 35 and 50 percent 6 of land to parking – roughly twice as much as the cities in this study. These large 7 differences might be explained partly by presumed lower land values in these town 8 centers; however, this view ignores the potential of parking oversupplies to actually 9 contribute to land devaluation (9, 19). In either case, large surface lots on lower-value 10 land are likely the only cost-effective way to achieve parking supply ratios in that higher 11 range. 12 13

14 FIGURE 1 Parking ratios versus land for parking in six cities and six towns in 15 2000. 16 17 Costs Associated with Parking Ratios 18 Depending on how parking ratios are achieved –through land consumption, increased 19 parking intensity or lower building density – associated costs are incurred by either the 20 developer and property owner or by the government. Additional external costs are 21 incurred by society. 22

Construction costs are the most direct costs associated with increasing parking 23 ratios – incurred initially by the developer and recouped through parking fees, rent or sale 24 of the property. These costs vary considerably depending on the type of parking facility. 25 Surface parking is the least expensive at approximately $5,000 per space (24). A typical 26 multi-level parking structures costs between $15,000 to $20,000 per space (adjusted to 27 2009 U.S. dollars) (20, 24, 25). Parking structures below grade cost as much as $50,000 28 per space, depending on their depth (10, 26, 27). Parking structures account for 25 to 37 29 percent of parking capacity in Hartford, Lowell and New Haven (compared to more than 30 40 percent in surface lots) but only five percent or less in Arlington, Berkeley and 31 Cambridge. On-street parking accounts for 58 to 80 percent of parking spaces in the 32

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Parking ratio (spaces per 1,000 ft2)

Six cities Town centers



latter three cities at considerably lower cost, but these supplies usually do not count 1 towards satisfying parking requirements. 2

The alternative to multi-level or on-street parking, which both increase parking 3 intensity, is to devote a greater portion of land to parking (12, 19). This poses limitations 4 for developers with regards to how they can use land and it presents numerous external 5 costs including the impacts of impervious coverage (29), degradation of the built urban 6 environment (13, 19, 29) and a potentially weaker tax base (30). Moreover, excessive 7 parking supplies in any form might run contrary to a city’s long-term travel management 8 goals (31), as discussed more in t he following section. While some cities acknowledge 9 these costs in public documents (23), few weigh these costs explicitly in setting parking 10 requirements. 11 12 Parking Supplies and Automobile Use 13 One key factor that varies considerably among the cities in this study and that has been 14 previously linked to parking provision is the rate of automobile use (12, 21). Figure 2 15 shows the relationship between rates of automobile use and parking ratios for the six 16 cities in this study in 1960 and 2000 – indicating a clear positive association. To test this 17 relationship at higher rates of automobile use, data are also included for six small town 18 centers in New England from prior research by Marshall and Garrick (17). In this higher 19 range, the slope increases substantially, which can be explained partly by the fact that 20 there are fewer opportunities for shared parking in these places. However, these parking 21 facilities are also found to be only 50 percent occupied during peak periods, suggesting 22 there is excess supply in these places (17). 23 24

25 FIGURE Off-street parking ratios versus automobile use for six cities and six 26 towns. 27 28

While the nature of parking supply and demand is different in the two groups, this 29 finding raises important questions regarding the role that parking requirements play in 30 urban transportation policy. While excess parking might be viewed as acceptable in 31 locations with exceptionally high rates of automobile use, it also contributes to higher 32

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Cities, 1960 Cities, 2000 Town Centers, 2000



rates of automobile use in locations that support a wider variety of travel options (16, 32–1 34). Parking requirements exacerbate this in two ways. First, they improve the chances 2 that a potential driver will have guaranteed parking spot at a destination, increasing the 3 likelihood they will drive, given a choice. Second, they increase the supply of parking 4 without regard for the market, which lowers the value of parking (9, 19) and makes it 5 difficult to introduce pricing as a demand management strategy. Therefore, in addition to 6 influencing changes to the built environment and associated costs, parking requirements 7 that increase parking supplies over long periods of time undermine efforts to manage 8 travel demand and subsequently lead to higher rates of automobile use. Although the 9 relationship between automobile use and parking supply is complex, city governments 10 only have reasonable authority to regulate the latter. It is important that these regulations 11 help bring about outcomes that are in line with each city’s long-term goals and vision. 12 13 CONCLUSIONS 14 This study offers insight regarding actual parking supply ratios in urban centers and 15 changes in parking supply ratios over a period of 40 years. It also reveals how these 16 parking supply ratios compare to parking requirements and to common estimates of 17 parking demand. 18

Off-street parking supply ratios increased by more than 150 percent in three cities, 19 due primarily to a rapidly growing number of parking spaces. Parking supply ratios 20 decreased somewhat in three other cities, due to a combination of additional building 21 space and fairly consistent supplies of parking. Even with increasing parking supply 22 ratios in some cities, none of the cities achieved more than 90 percent of baseline parking 23 requirements – with typical supplies ranging between 40 and 60 percent of requirements. 24 This raises questions regarding the justification for parking requirements in urban areas 25 and also the theoretical impact that parking requirements would have on the built 26 environment over the long run if fully met. 27

The study demonstrates the potential impacts that parking requirements would 28 have on land use and the built environment. Higher parking supply ratios can only be 29 achieved through a combination of expensive parking structures, greater use of on-street 30 parking, considerable commitments of land to parking or lesser amounts of useable 31 building space. Greater commitments of land are the most common adaptation, raising 32 concerns regarding the numerous associated costs outlined above. 33

These findings build on prior work suggesting a need to better evaluate existing 34 parking supplies in urban areas and critically examine the role that parking requirements 35 play. While recognizing that some level of parking can benefit urban areas, this work 36 reveals the potential magnitude of impacts associated with a failure to manage parking 37 supplies. While this study offers some insight into what optimal levels of parking might 38 look like, additional research is needed to better understand how much parking exists in 39 urban areas, how those supplies are utilized and the factors that affect demand. Then, 40 necessary steps can be taken to align system-wide supplies with actual utilization and 41 with the long-term goals of these places. 42 43 REFERENCES 44 1. Flink, J. J. America adopts the automobile, 1895-1910. MIT Press, Cambridge, 45

Mass., 1970. 46



2. Norton, P. D. Fighting traffic : The dawn of the motor age in the American city. 1 MIT Press, Cambridge, Mass., 2011. 2

3. Mogren, E. G., and W. Smith. Zoning and traffic. Eno Foundation for Highway 3 Traffic Control, Saugatuck, Conn., 1952. 4

4. Ferguson, E. Zoning for Parking as Policy Process: A Historical Review. 5 Transport Reviews, Vol. 24, No. 2, 2004, pp. 177–194. 6

5. Ben-Joseph, E. ReThinking a lot : the design and culture of parking. MIT Press, 7 Cambridge, Mass., 2012. 8

6. Institute of Transportation Engineers. Parking Generation, 2nd Ed. ITE, 9 Washington, DC, 1987. 10

7. Insitute of Transportation Engineers. Parking Generation, 4th Ed. ITE, 11 Washington, DC, 2010. 12

8. Rowe, D., R. S. McCourt, S. Morse, and P. Haas. Do Land Use, Transit, and Walk 13 Access Affect Residential Parking Demand? ITE Journal, Vol. February, 2013, pp. 14 24–28. 15

9. Engel-Yan, J., and D. Passmore. Assessing Alternative Approaches to Setting 16 Parking Requirements. ITE Journal, Vol. 80, No. 12, 2010, pp. 30–34. 17

10. Manville, M., and D. Shoup. Parking, People, and Cities. Journal of the American 18 Planning Association, Vol. 131, No. 4, 2005, pp. 233–246. 19

11. Millard-Ball, A. Putting on their parking caps. Planning, Vol. 68, No. 4, Apr. 20 2002, pp. 16–21. 21

12. Shin, Y. E., V. R. Vuchic, and E. C. Bruun. Land Consumption Impacts of a 22 Transportation System on a City. Transportation Research Record: Journal of the 23 Transportation Research Board, Vol. 2110, Dec. 2009, pp. 69–77. 24

13. Mukhija, V., and D. Shoup. Quantity versus Quality in Off-Street Parking 25 Requirements. Journal of the American Planning Association, Vol. 72, No. 3, 26 2006, pp. 296–307. 27

14. Barter, P. A. Off‐Street Parking Policy without Parking Requirements: A Need for 28 Market Fostering and Regulation. Transport Reviews, Vol. 30, No. 5, Sep. 2010, 29 pp. 571–588. 30

15. McShane, M., and M. D. Myer. Parking Policy and Urban Goals: Linking Strategy 31 to Needs. Transportation, Vol. 11, 1982, pp. 131–152. 32

16. Marsden, G. The evidence base for parking policies - a review. Transport Policy, 33 Vol. 13, 2006, pp. 447–457. 34

17. Marshall, W. E., and N. W. Garrick. Parking at Mixed-Use Centers in Small Cities. 35 Transportation Research Record: Journal of the Transportation Research Board, 36 Vol. 1977, 2006, pp. 164–171. 37

18. Snyder, M. C. A Study of Parking Supply and Utilization in Neighborhood 38 Commercial Centers in the Puget Sound Region, Washington State. 1999. 39

19. Willson, R. W. Suburban parking requirements. Journal of the American Planning 40 Association, Vol. 61, No. 1, 1995, pp. 29–42. 41

20. Shoup, D. C. The High Cost of Free Parking. Journal of Planning Education and 42 Research, Vol. 17, No. 1, Sep. 1997, pp. 3–20. 43

21. McCahill, C., and N. Garrick. Automobile use and land consumption: Empirical 44 evidence from 12 cities. URBAN DESIGN International, Vol. 17, No. 3, May 45 2012, pp. 221–227. 46



22. Haerter-Ratchford, J. Parking Policies and the Physical Transformation of Cities: 1 Empirical Evidence from Six American Cities. University of Connecticut, 2013. 2

23. McCahill, C. T., and N. W. Garrick. Influence of Parking Policy on Built 3 Environment and Travel Behavior in Two New England Cities, 1960 to 2007. 4 Transportation Research Record: Journal of the Transportation Research Board, 5 Vol. 2187, Dec. 2010, pp. 123–130. 6

24. National Parking Association. Parking in America. Washington, DC, 2008. 7 25. Rowland, J. D. Parking Structure Cost Outlook for 2009. 2009. 8 26. National Parking Association. Parking in America: The Second Annual Review of 9

Parking Rates in North America. 2009. 10 27. Highland, R. Construction cost per space of a parking garage : seven points an 11

owner should consider when building a parking structure. Parking, Vol. 29, No. 6, 12 1990, pp. 24–30. 13

28. Shoup, D. C. In Lieu of Required Parking. Journal of Planning Education and 14 Research, Vol. 18, 1999, pp. 307–320. 15

29. Feitelson, E., and O. Rotem. The case for taxing surface parking. Transportation 16 Research Part D: Transport and Environment, Vol. 9, 2004, pp. 319–333. 17

30. Center for Neighborhood Technology. Paved Over. Chicago, IL, 2006. 18 31. Shoup, D. C., and R. W. Willson. Commuting, Congestion and Pollution: The 19

Employer-Paid Parking Connnection. 1992. 20 32. Hess, D. B. Effect of Free Parking on Commuter Mode Choice: Evidence from 21

Travel Diary Data. Transportation Research Record: Journal of the 22 Transportation Research Board, Vol. 1753, 2001, pp. 35–42. 23

33. Shiftan, Y., and R. Burd-Eden. Modeling Response to Parking Policy. 24 Transportation Research Record: Journal of the Transportation Research Board, 25 Vol. 1765, 2001, pp. 27–34. 26

34. Willson, R. W., and D. C. Shoup. Parking subsidies and travel choices: Assessing 27 the evidence. Transportation, Vol. 17, No. 2, 1990, pp. 141–157. 28

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