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Evaluating the Performance of Corridors with Roundabouts (2014)

Chapter: Chapter 2. Research Approach

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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Suggested Citation:"Chapter 2. Research Approach ." National Academies of Sciences, Engineering, and Medicine. 2014. Evaluating the Performance of Corridors with Roundabouts. Washington, DC: The National Academies Press. doi: 10.17226/22348.
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Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Evaluating the Performance of Corridors with Roundabouts Chapter 2–Research Approach Page 2-1 CHAPTER 2. RESEARCH APPROACH The major components of the research included the following steps: Establish the need for the project in terms of its place within the body of existing literature and practice. The results of this are documented in Chapter 1. Prepare a general framework to enable the comparisons of corridors using a variety of intersection control forms, including roundabouts, traffic signals, and stop control. Identify roundabout corridors in the United States and key characteristics for which a breadth of useful data can be obtained. Prepare and execute a data collection plan to identify a set of existing roundabout corridors, conduct interviews of corridor operators, and collect operational performance data. Analyze the collected field data to develop predictive models for operational performance suitable for inclusion in the Highway Capacity Manual and to assess performance relative to hypothetical “equivalent non roundabout corridors.” This chapter discusses the corridor comparison framework and the data collection plan, as well as background and summary information on the corridors selected for data collection. The data analysis plan is divided into three distinct components: (1) empirical data analysis, (2) development of predictive model for roundabout corridors, and (3) development and comparison of traditional (signalized or stop controlled) alternatives. Data analysis is discussed in Chapter 3. 2.1. CORRIDOR COMPARISON DOCUMENT A key product of this research—the foundation supporting the remainder of the research—is a framework to enable objective comparisons across various corridor treatments. The outcome of this work is called a Corridor Comparison Document (CCD). It is further discussed in Chapter 4 and presented in its entirety in Appendix A. In general, the corridor comparison approach highlights topics practitioners use for guidance in their decision making process when considering alternatives for a new corridor or converting a corridor from traffic signals to roundabouts. The CCD considers these issues in terms of tiers, where certain tiers have broader application to all roundabout corridors and others have lesser applicability while being useful as potential differentiators if considerations do not provide sufficient input. The classification used in the CCD is as follows: Tier I – critical considerations for all types of corridors (e.g., delay, travel time, constructability).

Evaluating the Performance of Corridors with Roundabouts Page 2-2 Chapter 2–Research Approach Tier II – items that apply to many locations (e.g., access management, safety, pedestrian accessibility). Tier III – issues that may impact a smaller subset of corridors (e.g., effects on specific adjacent land uses such as schools or hospitals, familiarity of corridor drivers with roundabout operations). Conceptually, these considerations can be separated into two broad categories: quantitative elements and qualitative elements. Quantitative elements, which promote a model driven approach, are related to the operational models, data collection, and recommended analysis methodology. Qualitative elements include more anecdotal evidence and other considerations along the corridor that should be considered when weighing a roundabout corridor against a signalized arterial. The CCD is intended to be an easy to access summary of corridor evaluation considerations and to offer practitioners easy and functional insights into the considerations and trends of the research findings. By providing users with an understanding of the evaluation consideration concepts, users will have the basis for applying the results of this research within the context of their own project environments and fully supplemented by other performance measures not investigated as part of this project. The framework has several key components: It includes a discussion of performance measures that may be applicable when evaluating corridors where roundabouts or signals are being considered. It includes guidance on how to assess performance measures. Guidance often refers readers to other documents focused on specific performance measures. The CCD presents four examples on how to use the document. Examples present fictional corridor studies where roundabout and signal alternatives are under consideration. 2.2. STUDY SITE IDENTIFICATION The research team identified 58 corridors as potential study sites for use in this project. The corridors were located in 18 different US states, and they included single lane and multilane roundabouts. Per the definition of roundabout corridors in the RFP for this project, all 58 candidate corridors had at least three roundabouts in series, but several had five or more (up to ten) roundabouts in series. These are shown in Exhibit 2 1 and listed in Exhibit 2 2, along with a summary of selected site characteristics that made them promising candidate sites.

Evaluating the Performance of Corridors with Roundabouts Chapter 2–Research Approach Page 2-3 Exhibit 2-1: Known Roundabout Corridors, 2011 (Map)

1 AZ 179 Sedona Coconino AZ 6 3.2 1.9 2 1 Suburbanizing Rural No RIRO and some median breaks No No Signals and TWSC 2008 2011 2 AZ 179 Oak Creek Yavapai AZ 4 1.1 3.6 2 1 Suburbanizing Rural No RIRO and some median breaks No No Signals 2008 3 Cactus Rd Scottsdale Maricopa AZ 3 1 3 2 1 Suburban Residential No TWLTL, many driveways No Some TWSC 2008 4 La Jolla Blvd San Diego San Diego CA 4 0.6 6.7 2 1 Urban Yes Median, many driveways No Some 2 signals, 2 TWSC; TWLTL 2005 and 2008 5 O'Neill Dr San Juan Capistrano Orange CA 4 0.9 4.4 2 1 Suburban Residential No 1 median break, not many driveways No Some New 2003 6 Sienna Pkwy San Juan Capistrano Orange CA 5 1 5 2 1 Suburban Residential No Several median breaks for driveways No Some New 2002 7 Fulton Ave Ripon San Joaquin CA 3 1 3 3 4 1 Suburban No Frontage road, some full access driveways No No New 2006 8 Manzanita Ave Chico Butte CA 3 0.6 5 2 1 Suburban Residential No Full access No No Mixture 2008 or 2009 9 8th Ave Chico Butte CA 3 0.8 3.8 2 1 Suburban Residential No Full access No No Probably TWSC Between 2002 and 2005 10 Avon Rd Avon Eagle CO 5 0.5 10 4 2 Suburban No Two side streets Yes No Unknown 1997 11 Golden Road Golden Jefferson CO 5 1 5 4 2 Suburban No Many mix of RIRO and full access No No Unknown 1998 (one added 2009) 12 William J. Post Blvd Avon Eagle CO 6 1 6 4 2 Suburban No 1 full driveway Yes No New Between 1999 and 2004 13 Lake Ave Colorado Springs El Paso CO 3 0.9 3.3 2 1 Suburban No TWLTL, many driveways No Some Unknown 1999 or earlier 14 Lowry Blvd Denver Denver CO 3 0.8 3.8 4 2 Suburban No Some full access and RIRO driveways No No Signals 1998 15 Hagen Ranch Rd Boynton Beach Palm Beach FL 5 2.2 2.3 2 1 Suburban Residential No A few si e streets No No Unknown 1998 2004 16 Morse Blvd The Villages Sumter FL 6 3.3 1.8 4 2 Suburban No No driveways No Many New 2003 2007 17 Buena Vista Blvd (southern) The Villages Sumter FL 10 4.8 2.1 4 2 Suburban No No driveways No Many New 2003 2007 18 Buena Vista Blvd (northern) The Villages Sumter FL 4 2.7 1.5 4 2 Suburban No No driveways No Some New 1998 2001 19 Spring Mill Road Carmel Hamilton IN 7 4.5 1.6 2 1 Suburban No Many full access side streets No Many Stop control 2008 2010 20 Old Meridian Street Carmel Hamilton IN 4 1.3 3.1 4 2 Suburban Limited RIRO and some median breaks No Some Signals 2007 2008 21 WMain St Carmel Hamilton IN 5 2.2 2.3 2 1 Suburban Residential No Many full access side streets No Many Stop control 2005 present 22 W 136th St Carmel Hamilton IN 4 3 1.3 2 1 Suburban Residential No Many full access side streets No Many Stop control 2005 present 23 Wanamaker Rd Topeka Shawnee KS 3 2 1.5 4 1 2 Suburban Residential No TWLTL, many driveways No Some Mixture 2006 2007 24 Sheridan Rd Olathe Johnson KS 2 0.3 6.7 3 4 1 2 Suburban No Many driveways No Some Unknown 2000 2001 25 Renner Lenexa Johnson KS 4 0.4 10 4 2 Suburban No Median with 1 right in No No TWSC 2007 26 Prairie Star Pkwy Lenexa Johnson KS 7 1.2 5.8 4 2 Suburban No Median and no driveways No Some New 2009 27 Scaggsville Rd (MD 216) Scaggsville Howard MD 4 0.7 5.7 4 2 Suburban Retail No No driveways Yes Some Interchange was at grade with signal 2002 2009 28 Hampstead Bypass (MD 30) Hampstead Carroll MD 3 4.4 0.7 2 2 Rural No Expressway No driveways No No New 2009 2010 29 Maple Road Farmington Hills Oakland MI 2 1 2 2 3 Suburban No Many full access side streets No No Signals 2008 or 2009 30 Village Place Blvd West Bloomfield Livingston MI 4 0.4 10 4 2 Suburban Retail No 2 full driveways Yes No Signal and TWSC 2006 31 Longview Blvd Lee’s Summit Jackson MO 3 0.5 6 4 2 Suburban No Many full access side streets No Some New 2005 32 Metro Parkway Jackson Hinds MS 5 1.3 3.8 4 2 Becoming Urban No RIRO No Some New 2004 2006 33 Shiloh Road Billings Yellowstone MT 8 3.3 2.4 ? 2 Suburban No Many full access side streets No Some Mostly stop control 2009 2010 34 Hillsborough St Raleigh Wake NC 2 0.5 4 4 1 and 2 Urban No Many full access side streets No Some Signal and TWSC 2010 35 SR 67 Malta Saratoga NY 7 1.6 4.4 4 2 Suburban No Median, many RIROs Yes No Mostly TWSC 2006 36 SR 85 Slingerlands Albany NY 4 1.2 3.3 4 2 Suburban No Median, several RIROs No No Mostly new 2007 37 SR 590 Irondequoit Monroe NY 4 1.1 3.6 4 1 Suburban Residential No Expressway No driveways No No Signals 2010 38 US 62 Hamburg Erie NY 4 1 4 2 1 Small Town Yes Many full access side streets No No Signals 2007 and later 39 NW Crossing Bend Deschutes OR 5 1.2 4.2 2 1 Suburban No Many No Many TWSC and new 2005 2006 Length (mi) Inter change? Adjacent Rdbts? Previous Control Approx Year Built Road Name / Route Number Rbts / mi Arterial Lanes Rbt Lanes Land Use On Street Parking? Access ManagementCity County State # Rbts Evaluating the Performance of Corridors with Roundabouts Page 2-4 Chapter 2–Research Approach

40 Reed Market Dr Bend Deschutes OR 5 1.1 4.5 4 2 Suburban No Median and no driveways No Some New facility 2002 41 14th St Bend Deschutes OR 4 1.7 2.4 2 1 Suburban No Many full access side streets No Many Unknown 1999 2005 42 Maple Island Rd Eugene Lane OR 3 0.2 15 2 1 Suburban Retail No No driveways No No New development 2002 43 Via Bella Williamsport Lycoming PA 3 0.3 10 2 1 Urban No No driveways No No Signals Between 2005 and 2008 44 Littlerock Rd Olympia Thurston WA 4 1.1 3.6 2 1 Suburban No Many driveways No No 3 TWSC, 1 signal 2009 2010 45 Grandview Dr University Place Pierce WA 5 1.2 4.2 2 1 Suburban Residential No Some full access side streets No No Stop control 2000 46 Borgen Blvd Gig Harbor Pierce WA 4 1.4 2.9 4 2 Suburban No Mixture of full and RIRO Yes Some Unknown 2000 2007 47 Dike Access Rd Woodland Columbia WA 3 0.2 15 2? 1 Suburban No No driveways Yes No TWSC 2010 2011 48 SR 539 Lynden Whatcom WA 4 6.5 0.6 4 2? Suburban No unknown No No mixture 2009 2010 49 SR 11/SR 20 Burlington Skagit WA 3 0.5 6 2 2 Suburban No Many full access driveways Yes No Unknown 2008 2010 50 Valley Mall Blvd Yakima Yakima WA 3 0.2 15 4? 2 Suburban No No driveways Yes No 2 signals, 1 TWSC 2010 2011 51 SR 145 Richfield Washington WI 5 0.6 8.3 2 and 2 1 and 2 Suburban No Some full access driveways Yes No TWSC 2009 52 Sheuring Rd Green Bay Brown WI 3 1 3 2? 1? Suburban No Many full access driveways No No stop control 2004 53 Lineville Rd Green Bay Brown WI 5 1 5 2 1 Suburban No Some full access driveways No No stop control 1999 2007 54 Springdale St Mt. Horeb Dane WI 5 1.4 3.6 4 2 Suburban No Some full access driveways No No unknown, some new 2004 2006 55 SR 42 Sheboygan Sheboygan WI 3 0.4 7.5 4 2 Suburban No No driveways Yes No unknown 2007 56 CR O Rice Lake Barron WI 3 0.4 7.5 2 1 Small Town/Suburb an No 1 right in Yes No stop control 2006 57 Chicago St Green Bay Brown WI 3 0.5 6 2 1 Suburban No Some full access driveways No No Unknown 2001 58 Evergreen Dr Appleton Outagamie WI 3 0.5 6 2? 1? Suburban No No driveways Yes No 2 signals, 1 TWSC 2010 2011 Access Management Inter change? Adjacent Rdbts? Previous Control Approx Year Built Rbts / mi Arterial Lanes Rbt Lanes Land Use On Street Parking? Road Name / Route Number City County State # Rbts Length (mi) Evaluating the Performance of Corridors with Roundabouts Chapter 2–Research Approach Page 2-5

Evaluating the Performance of Corridors with Roundabouts Page 2-6 Chapter 2–Research Approach Of these corridors, the research team prioritized the potential sites, based on the team’s judgment as to which corridors appeared to have the most promise for positive research outcomes. Foremost, sites were selected if the research team believed they had sufficiently high volumes from which meaningful traffic operations results could be obtained. The research team assessed this based upon land use and, in some cases, team members’ knowledge of study corridors. The research team also considered the range of possible project catalysts that may have led to the initial corridor evaluation. These catalysts help establish a project context and influence the type of data that may be useful in conducting corridor comparisons. The range of project catalysts included: A new greenfield corridor An existing signalized corridor being evaluated because of capacity or safety performance An existing roundabout corridor A corridor with a specific access management focus A corridor explicitly focused on multimodal considerations A corridor project driven by community enhancement objectives, speed management needs, or economic development or growth opportunities Beyond this, the site selection was guided by a variety of qualities and contexts, including: Saturated/unsaturated flow conditions Corridor land uses (commercial, residential, etc.) Time of day variations Roundabout density (spacing) Wide range of motorized and non motorized users Roundabout types (single vs. multilane) Low vs. substantial side street traffic How long the roundabouts had been operating Type of access management and intersection controls within the corridor Geographic diversity Efficiency of data collection (proximity to other sites to consolidate travel costs, etc.) Number of roundabouts Mixture of land use Range of posted/operating speeds Corridor length and roundabout spacing Presence/absence of traversable median and/or curb

Evaluating the Performance of Corridors with Roundabouts Chapter 2–Research Approach Page 2-7 Presence/absence of sidewalks and/or bicycle lanes Presence/absence of on street parking With these elements in mind, the research team identified the following nine roundabout corridors from the list as preferred data collection sites: MD 216 in Scaggsville, Maryland La Jolla Boulevard in San Diego, California Old Meridian Street in Carmel, Indiana Spring Mill Road in Carmel, Indiana Borgen Boulevard in Gig Harbor, Washington SR 539 in Whatcom County, Washington Golden Road in Golden, Colorado Avon Road in Avon, Colorado SR 67 in Malta, New York Full field data reports for these nine corridors are included in the NCHRP web only document accompanying this report as Appendices B through J. Photos of the corridors taken by the research team are included in the web only document as Appendix K. A later section of this chapter presents a summary of data from the nine corridors. 2.3. DATA COLLECTION PLAN 2.3.1. PILOT SITES In developing the procedure to collect the field data for this project, the research team wanted to ensure the procedure was flexible enough to be effective at corridors with a variety of characteristics. As shown in Exhibit 2 2, the corridors under consideration varied widely in geographical location, number of roundabouts, corridor length, roundabout spacing, and other key variables. As a result, the team sought a data collection procedure that would capture meaningful data under varied conditions. The team conducted pilot studies at two corridors, and revised the data collection procedure for use at the remaining seven locations. Pilot studies are commonly used in research projects to develop data collection procedures. Pilot sites were selected with the intent of including as many key site characteristics as possible. Geographical location, adjacent land use, expected vehicle speeds, corridor length, and roundabout spacing were all considered in the selection of pilot sites. Using the corridor information summarized in Exhibit 2 2, and considering the ability of the team to obtain further information (e.g., as built plans, traffic volumes) from the appropriate road agency, the researchers looked for the corridors with the greatest potential for providing useful data as well as information on the appropriateness of the data collection procedure.

Evaluating the Performance of Corridors with Roundabouts Page 2-8 Chapter 2–Research Approach The research team selected two corridors to use as pilot sites: Maryland State Route 216 (MD 216) in Scaggsville, Maryland, and La Jolla Boulevard in San Diego, California. The corridor on MD 216 is located in a suburban area between Washington, D.C., and Baltimore. MD 216 is a four lane divided roadway and has four roundabouts, two of which are at ramp terminals as part of the interchange with US 29. There are no intermediate access points between any of the roundabouts. The corridor is automobile dominated, with lile pedestrian or bicycle activity. The La Jolla Boulevard corridor is located in the Bird Rock neighborhood of San Diego. La Jolla Boulevard is a two lane divided roadway with five roundabouts. Much of the roadway has bicycle lanes and on street parking (either parallel or diagonal). All intermediate access points are right in, right out, and most are driveways to houses or parking lots with 20 or fewer spaces. The corridor has an urban character with a moderate degree of pedestrian and bicycle activity. 2.3.1.1. Data Collection Techniques The objective of the team’s proposed data collection plan was to emphasize flexibility. The initial pilot data collection procedure was designed so many performance measures could be collected, depending on input from the project panel. One of the key performance measures for roundabout corridors was defined as the travel time of through traffic and other key origin destination pairs. To obtain that data, the research team designed a data collection procedure for the pilot sites that included multiple travel time data collection techniques, which are described in the following paragraphs. Bluetooth Technology in the form of multiple roadside units at fixed locations recorded signature identification numbers (MAC addresses) of Bluetooth equipped cell phones and other devices of the traffic stream. It is a non intrusive data collection reliably capturing travel times of approximately 10% of the traffic stream. Bluetooth measurements are made continuously, providing a 24 hour distribution of travel times. The technology is therefore uniquely capable of quantifying the variability of travel times throughout the day, and further provides a high sample size for statistical comparisons. In general, several challenges exist in applying Bluetooth data to surface street corridors. First, the presence of driveways results in frequently interrupted trajectories, and these intermediate stops are not registered by Bluetooth units at the termini. Second, depending on local traffic paerns, the fraction of vehicles actually traveling the entire corridor may be limited. And third, an urban corridor is likely to have a significant portion of non automobile users; Bluetooth devices used by bicyclists, pedestrians, or transit passengers may not be distinguishable from those in passenger vehicles, depending on congestion levels. In fact, on congested corridors a bicyclist may traverse the corridor faster than a vehicle. To help overcome these issues, the team decided to use GPS travel time data to calibrate the Bluetooth data extraction. Using a known Bluetooth MAC address of a device in the GPS probe vehicle, defined benchmarks were created to help filter the remaining data.

Evaluating the Performance of Corridors with Roundabouts Chapter 2–Research Approach Page 2-9 GPS Technology, in the form of an in vehicle data logger, continuously recorded the speed and position of the vehicle as it traveled along the corridor (in 1 second intervals). GPS travel time trajectories provide a detailed assessment of travel characteristics, as travel time data supplemented by speed profiles, delay estimates, and the number of stops along the traveled path. Specifically for roundabout corridors, GPS unit data readily provided an estimate of the geometric delay (relative to free flow speed) associated with individual roundabouts. In designing the travel time runs, the research team proposed to have one vehicle continuously loop through a pre defined route extending beyond the beginning and end of the corridor. The vehicle operated during peak and off peak periods, allowing the GPS unit to collect data in both periods to calibrate the continuous Bluetooth monitoring. Another benefit of collecting data during off peak periods was to obtain a sample of free flow trajectories to estimate the geometric delay incurred at roundabouts. During the first pilot study (MD 216), the research team decided to conduct GPS travel time runs for routes involving left turns onto and off of the corridor in addition to through routes. These additional runs were conducted because the corridor was relatively short and there was time remaining after through route data were collected. Also, to account for unforeseen issues, the team brought additional staff and vehicles to the first site. All travel time runs were logged on manual tally sheets, where the driver recorded the starting time, end time, and any noteworthy events for every route. This record was completed at the turnaround points to prevent any distractions during driving. A subset of GPS runs was further supplemented with in vehicle video records of the traveled route. These recordings were made with the intent that they would be useful to present features of a particular roundabout corridor to the panel or other audience. The team also felt video recordings are useful to review certain features of the corridor after returning to the office. Exhibit 2 3 shows the routes of the four left turn travel time runs conducted on MD 216, and Exhibit 2 4 shows the routes of the four left turn travel time runs conducted on La Jolla Boulevard. Through runs were also conducted on each corridor, but they are omitted from the exhibits below for clarity. Exhibit 2-3: Schematic of Left- Turn Travel-Time Routes for MD 216

Evaluating the Performance of Corridors with Roundabouts Page 2-10 Chapter 2–Research Approach The corridor travel times, estimated through a combination of both approaches and the travel time data, were further supplemented with other data collection technologies: Tally Sheets: Many of the necessary data collected as a part of a roundabout corridor evaluation can be quickly gathered in the field using tally sheets from a good vantage point, including delay and queue measurements. The research team applied video to some extent to provide a permanent record of conditions during the field study and to collect data items difficult to observe in the field in real time; however, tally sheets improved the economy of office data extraction for readily observed measures. The tally sheet data collection approach provided a fast, efficient method of documenting necessary data by the time the team left each data collection site. Tally sheets were also critical for any of the more qualitative and perception based corridor characteristics, including access management practices, pedestrian and bicycle accommodations, and construction details. A structured field survey form assured consistency across sites and inter observer reliability. Video: To collect traffic volume, the research team used video recording. In addition to recording the traffic movements at each roundabout in the study corridor, video was used to create a 12 hour volume profile of the corridor. Members of the research team brought video cameras to MD 216, set them up, and later played back videos to count vehicles. The time and effort required to transport, set up, and operate video cameras proved to be substantial. The cameras and equipment for attaching them to poles were transported via airplane in an overweight piece of baggage. A ladder was required to set up the cameras at an adequate vantage point on poles or tree trunks. The cameras had to be taken down between Day 1 and Day 2 to recharge batteries, transfer video files, and prevent theft or water damage if there was rain. Transferring video files in preparation for Day 2 took much of the night. Considering these issues, the research team employed Quality Counts, LLC, to collect video data and perform turning movement counts at La Jolla Boulevard. The Quality Counts camera setup was capable of recording video continuously for approximately 60 hours in any weather conditions. The cost of using Quality Counts to record video data and perform turning movement counts from the video at La Jolla Boulevard was approximately the same as the cost to use the research team’s own resources at MD 216 and yielded a larger sample of data. Exhibit 2-4: Schematic of Left-Turn Travel-Time Routes for La Jolla Boulevard

Evaluating the Performance of Corridors with Roundabouts Chapter 2–Research Approach Page 2-11 Lidar: The research team also wanted to directly collect a selection of speed data at key locations for comparison to the speed data obtained from the other data collection methods. To fulfill that need, the researchers used a handheld lidar gun to measure speeds, which were recorded manually on tally sheets. The researchers measured spot speeds of traffic entering the roundabout at each end of the corridor, as well as traffic circulating within those two roundabouts. A total of 30 spot speed measurements were recorded at each point. Photographs and Handwrien Notes: The research team took additional notes as needed on physical measurements of key geometric features, predominant adjacent land use, and other site characteristics of note. The research team also further documented the conditions at each site with digital photographs of features of each roundabout and corridor, as well as additional noteworthy characteristics of each site. The research team created an electronic repository of pertinent site characteristics collected at the study sites. This includes electronic files of data tables, digital copies of video recordings, and scans of handwrien notes and tally sheets. The electronic record enabled data sharing among the team and protected the data over time. 2.3.1.2. Agency-Provided Data Some data elements were not readily obtained in the field, but instead from operating agencies. Local agencies provided copies of as built construction plans and any existing traffic volume data. Researchers also interviewed state and local transportation personnel (discussed in a later section of this chapter) to obtain additional first hand experiences with the roundabout corridors. 2.3.1.3. Collection Schedule During the pilot phase, the team proposed a two stage data collection schedule, using a combination of data enhanced scouting trips and full detail data collection trips. The scouting trips were scheduled for two team members to complete over 1.5 days. The purpose of these trips was to make initial field observations and determine usability for data collection. To maximize the use of project resources, the team proposed to use this initial scouting trip for some preliminary data collection. Specifically, the team conducted a sample of GPS travel time runs, recorded some video, and conducted a structured field survey of other corridor characteristics. The intent was that these scouting trips would then be followed up by detailed data collection trips at a selected number of sites. 2.3.1.4. Findings from Pilot Data Collection The research team scouted and collected data at the two pilot corridors (MD 216 and La Jolla Boulevard) in the fall of 2011. After reviewing the data obtained and discussing the experiences at those two sites, the research team determined some changes could be made to the data collection procedure. These changes were discussed with the project panel and refined based on the panel’s input. As a result of the pilot data collection and discussions with the panel, the research team made the following conclusions:

Evaluating the Performance of Corridors with Roundabouts Page 2-12 Chapter 2–Research Approach A two phase data collection schedule was not necessary; there was sufficient time within a single three day trip to collect the needed data at a study site. Extending the study period to three days provided the time needed to take pictures and compile field notes in addition to the other needed data collection. Video recorders could be installed prior to the three day period and removed afterward to maximize the recording time. The equipment needed to be “efficiently portable.” While all of the equipment used in the pilot data collection effort was useful to varying extents, it was not always the most efficient means of obtaining data. For example, the Bluetooth equipment provided marginally useful data on the longer corridor of MD 216 and operated efficiently once on site, but it was expensive to transport and less useful on the shorter La Jolla Boulevard corridor with its closer roundabout spacing and on street friction. In general, the Bluetooth equipment was useful at providing corridor wide data, but was unable to capture more detailed data such as geometric delay at a specific roundabout or operating speed on a specific midblock segment. Video recorders needed to be robust enough to record for long periods of time without external memory or power. The team made improvements in the video recording procedures between the two pilot studies, which were successful in improving efficiency. Also, they needed to be portable enough to easily transport from place to place and to mount in locations that would provide the needed point of view of each intersection. Use of Quality Counts, LLC, was superior to use of the team’s own equipment and labor. GPS data was sufficient in providing data on travel time within the corridor. While having supplemental Bluetooth data was somewhat useful, it was deemed unnecessary in comparison to the effort and cost required to transport and install the devices. Other data items, while potentially informative, were determined to not be critical to the needs of the project. As a result, the research team consolidated the data items collected, which improved the efficiency of the data collection procedures and allowed for the revised three day schedule. Section 2.3.2 describes the revised data collection procedure in more detail. 2.3.2. REVISED DATA COLLECTION PROCEDURE The following is a description of the data collection procedure revised to reflect the team’s experience with collecting data at the two pilot sites. The team used this procedure at the seven other data collection sites. The team focused its field data collection on GPS based travel time, spot speed measurements at critical locations, and a walk through survey and photo log of the corridor. In addition, the team comprehensively deployed video equipment to capture the equivalent

Evaluating the Performance of Corridors with Roundabouts Chapter 2–Research Approach Page 2-13 of (at least) one 12 hour period on video over two consecutive days for each roundabout along the corridor. The purpose of the video recordings was primarily to extract approach volume counts and intersection turning movement counts. One additional variation in the data collection protocol was the explicit consideration of selected left turning movements along the corridor in the travel time studies. As such, the team used GPS units to collect travel time data on up to four left turning movements into or out of each corridor. This data collection was in addition to the amount of through movement data collection already proposed for collection, and was designed to provide supplemental data to create a more comprehensive look at the side street performance of roundabout corridors. The revised data collection plan required a team of two personnel over a three day period. The following data were collected during each trip: Travel time data (via vehicle mounted GPS units) – AM Peak (2 hours × 2 days), PM Peak (2 hours × 2 days), Off Peak Midday (2 hours × 2 days), Off Peak Evening (2 hours) o Through movement runs over the entire corridor o Two routes with left turns onto the corridor o Two routes with left turns off of the corridor at a roundabout The left turn routes were selected based on a preliminary assessment of those movements likely to experience the most delay and/or variation throughout the day. Left turn routes without nearby turnaround points, such as routes involving freeway on or off ramps, were generally avoided. Spot speeds (via lidar gun) – Entering and circulating free flow speed at two approaches to two different roundabouts at a sample size of 30 observations each. Site characteristics – Gathered during a walk through in both directions, associated with a detailed photo log of the corridor and critical side streets. Video observations – Video collected for equivalent of a 12 hour period from overhead camera locations for the following data items: 1. Turning movement counts 2. Midblock volumes 3. Pedestrian and bicycle volume and operations

Evaluating the Performance of Corridors with Roundabouts Page 2-14 Chapter 2–Research Approach 4. Arrival paerns (platooning) For reasons previously discussed, the team used a vendor to collect video data and conduct counts from the video. The extensive time spent at the corridor allowed the research team to qualitatively assess operational characteristics that were not explicitly captured by the data collection plan. For example, queue lengths were not recorded, but research team members were able to observe if queues from a roundabout spilled back to an adjacent roundabout and impacted its operations. Use of the GPS units and speed guns, as well as the procedure for documenting site characteristics, remained largely the same as the process in the pilot study effort. The primary differences between the pilot data collection and the revised data collection were eliminating Bluetooth data collection and using a vendor for collecting and processing video data. As discussed in Section 2.3.1.4, while the Bluetooth units had potential for providing a great deal of data, the datasets were not as useful as originally envisioned, and transporting the units was cumbersome and expensive. Exhibit 2 5 outlines how the research team ultimately used each of the data collection techniques to capture the necessary data. Data/Performance Measures Means of Collecting Data Corridor travel time GPS Operating speed and speed profiles/variability through corridor Speed gun samples, GPS Pedestrian and bicycle volumes Video records Approach delay GPS Travel time for side-street trips with left turn onto/off of side street GPS Peak period turning-movement counts Video records Twelve-hour corridor-volume profile Video records Design characteristics (median type, number of driveways, presence/absence of sidewalks, etc.) Photographs, notes Exhibit 2 6 displays the work schedule to collect each of these types of data with a staff of two people over a three day period. The efficiencies obtained in the revised schedule also made it possible to sufficiently study and document a pair of sites within a five day period, as shown in Exhibit 2 7. The schedules show the responsibilities of the two staff members (1 and 2) associated with each data item. The schedule was designed to be generous in the allocation of time to each data item, allowing flexibility in the event that rain or unforeseen complications arose. The schedule also provided time for breaks, which were critical for long data collection days that involved a great deal of driving on repeated round trips through each site’s travel time routes. Exhibit 2-5: Application of Data Collection Techniques

Evaluating the Performance of Corridors with Roundabouts Chapter 2–Research Approach Page 2-15 Exhibit 2-6: Work Schedule for Single-Site Data Collection 7-9 9-11 11-1 1-3 3-5 5-7 6-7 7-9 9-11 11-1 1-3 3-5 5-7 7-9 9-11 11-1 Site Characteristics (Tally) 1,2 1 1 Corridor travel time through (GPS) 1 1 1 1 1 1 Corridor travel time left turns (GPS) 2 2 2 2 2 2 Spot Speed Measurements (Tally) 2 2 2 2 Miscellaneous Studies (Video) SETUP 3 V V V V V V V V V V V V V Take- Down B# - Break + Analyst # Data Item 3- Quality Counts Staff Day 1 Day 2 1 - Staff Person 1 K IC K O F F M E E T IN G / S C O U T C O R R ID O R Day 3 LU N C H D E B R IE F IN G LU N C H 2 - Staff Person 2 E - Equipment V - Video

Eva lu a tin g th e Pe rfo rm a n c e o f C o rrid o rs w ith R o u n d a b o u ts Page 2-16 Chapter 2–Research Approach Exh ibit 2-7: W ork Schedule for D ouble-Site D ata C ollection Day Data Item 1-3 3-5 5-7 7-8 8-10 6-7 7-9 9-11 11-1 1-3 3-5 5-7 7-8 8-10 6-7 7-9 9-11 11-1 1-3 3-5 5-7 Site Characteristics (Tally) 1,2 1 1 Corridor travel time through (GPS) 1 1 1 1 1 1 1 1 Corridor travel time left turns (GPS) 2 2 2 2 2 2 2 2 Spot Speed Measurements (Tally) 2 2 2 2 2 Miscellaneous Studies (Video) V V V V V V V V V V V V V V V V V V V Take- Down L U N C H B a c k u p B a c k u p B a c k u p D E B R I E F I N G D I N N E R L U N C H D I N N E R 3 4 5 Day Data Item 7-9 9-11 11-1 1-3 3-5 5-7 7-8 8-10 6-7 7-9 9-11 11-1 1-3 3-5 5-7 7-8 8-10 7-9 9-11 11-1 Site Characteristics (Tally) 1,2 1 1 Corridor travel time through (GPS) 1 1 1 1 1 1 1 1 Corridor travel time left turns (GPS) 2 2 2 2 2 2 2 2 Spot Speed Measurements (Tally) 2 2 2 2 2 Miscellaneous Studies (Video) SETUP 3 V V V V V V V V V V V V V V V V V V B# - Break + Analyst # 3 1 - Staff Person 1 E - Equipment 2 - Staff Person 2 V - Video 3- Quality Counts Staff B a c k u p B a c k u p L u n c h - D e b r i e f K I C K O F F M E E T I N G / S C O U T C O R R I D O R L U N C H D I N N E R L U N C H D I N N E R 1 2

Evaluating the Performance of Corridors with Roundabouts Chapter 2–Research Approach Page 2-17 2.4. SITE CHARACTERISTICS SUMMARY As discussed previously (Section 2.2), the research team identified 58 roundabout corridors in the United States. Two were visited during the pilot study data collection in Phase I, and an additional seven corridors were visited in Phase II. The nine corridors studied represent a diverse set of US roundabout corridors. They include the following range of aributes: The sites represent good geographic diversity, including east coast, midwest, mountain west, and west coast states. The number of roundabouts per corridor ranged from four to seven. The corridors were a mix of two lane and four lane arterials. The roundabouts were a mix of single lane and multilane roundabouts. Speed limits ranged from 25 mph to 50 mph. Corridor lengths ranged from 0.5 miles to 4.5 miles. Corridor average roundabout spacing ranged from 650 feet to 6,465 feet. Land uses were primarily suburban, with one urban corridor and one rural corridor. Four corridors included a freeway interchange. Opening dates ranged from 1997 to 2011. Seven corridors had a non traversable median for a portion of the corridor. The number of driveways ranged from 0 to 67. Two corridors had on street parking. Eight corridors had sidewalks and crosswalks at the roundabouts. Two corridors had bike lanes. Peak hour traffic volume and side street traffic volume varied greatly along some corridors. Twelve hour (7 a.m. to 7 p.m) arterial volumes measured near the midpoint of each corridor ranged from 9,000 to 23,000. The research team selected corridors believed to have moderate to high traffic volume based on land use and the team’s personal knowledge of the corridors because a wide range of traffic volumes is desirable when developing operational models. However, roundabouts remain relatively new in the United States, and most roundabout corridors are in the early years of their design life. As a result, traffic volumes have not grown to design year forecasts, and capacity is available. Generally speaking, the study corridors were observed to operate below capacity with low delays during all periods of study (a.m. peak, p.m. peak, and off peak). The field data collection approach (i.e., floating car runs along the arterial) collected only a small sample of side street approach delays as

Evaluating the Performance of Corridors with Roundabouts Page 2-18 Chapter 2–Research Approach part of travel time runs involving left turns, but based on the team’s observations they were generally similar to the arterial approach delays. Exhibits 2 8, 2 9, and 2 10 present a summary of characteristics of the nine study corridors. N um be r of R ou nd ab ou ts Ar te ria l # L an es R ou nd ab ou t # L an es Po st ed S pe ed L im it (m ph ) Co rr id or L en gt h (m i) Av er ag e R ou nd ab ou t Sp ac in g (f t) Ar ea T yp e In cl ud es I nt er ch an ge C on st ru ct io n Ye ar MD 216 (Scaggsville, MD) 4 4 2 45 0.7 1200 Commercial Yes 2002, 2009 La Jolla Boulevard (San Diego, CA) 5 2 1 25 0.6 715 Urban No 2005 to 2008 Spring Mill Road (Carmel, IN) 7 2 1 40 4.5 3950 Residential No 2005 to 2009 Old Meridian Street (Carmel, IN) 4 4 2 40 1.3 1640 Commercial/ Residential No 2006 Borgen Boulevard (Gig Harbor, WA) 4 4 2 35 1.4 1695 Commercial/ Residential Yes 2000 to 2007 SR 539 (Whatcom County, WA) 4 4 2 50 3.7 6465 Rural No 2010 Golden Road (Golden, CO) 5 4 2 25 to 35 1 1360 Commercial No 1998 to 1999, 2004 Avon Road (Avon, CO) 5 4 2 to 3 25 0.5 650 Commercial Yes 1997 SR 67 (Malta, NY) 7 2 to 4 1 to 2 35 to 45 1.6 1400 Commercial/ Residential Yes 2006 to 2011 Exhibit 2-8: Characteristics of Data Collection Sites

Evaluating the Performance of Corridors with Roundabouts Chapter 2–Research Approach Page 2-19 M ed ia n D riv ew ay s O n- St re et P ar ki ng Si de w al ks Cr os sw al ks Pe ak -H ou r Pe de st ria n Vo lu m es (I nt er se ct io n To ta ls ) Bi ke L an es MD 216 Raised 0 No Yes Yes Not counted No La Jolla Boulevard Raised 17 Yes Yes Yes 10 to 60 Yes Spring Mill Road Mostly none 33 No Var- ies Yes 0 to 12 No Old Meridian Street Mostly raised 22 Yes Yes Yes 0 to 10 No Borgen Boulevard Varies 8 No Yes Yes 0 to 4 Yes SR 539 Cable 67 No No Yes 0 to 8 No Golden Road Raised with openings 19 No Yes Yes 4 to 14 No Avon Road Raised, 1 opening 1 No Yes Yes 0 to 28 No SR 67 Raised, none 22 No Yes Yes 0 to 24 No Exhibit 2-9: Access Management and Pedestrian/Bicycle Characteristics of Data Collection Sites

Evaluating the Performance of Corridors with Roundabouts Page 2-20 Chapter 2–Research Approach Peak- Hour Traffic Volumes (Arterial) Peak- Hour Traffic Volumes (Side Streets) Measured 12-Hour Arterial Volume (7 a.m. to 7 p.m.) Roundabout Entering Speed (mph) Roundabout Circulating Speed (mph) MD 216 1,600 to 2,100 100 to 800 Not counted 23 21 La Jolla Boulevard 1,000 to 1,500 100 to 200 11,000 17 15 Spring Mill Road 1,100 to 1,600 200 to 1600 13,000 24 20 Old Meridian Street 500 to 1,200 80 to 1300 9,000 23 19 Borgen Boulevard 1,000 to 2,000 500 to 1400 14,000 18 15 SR 539 800 6 to 200 23,000 23 20 Golden Road 1,000 to 1,400 20 to 400 9,000 18 18 Avon Road 1,300 to 1,800 300 to 1000 13,000 N/A 16 SR 67 600 to 1,200 70 to 800 15,000 20 21 Exhibit 2-10: Volume and Speed Observations at Data Collection Sites

Evaluating the Performance of Corridors with Roundabouts Chapter 2–Research Approach Page 2-21 2.5. CORRIDOR OWNER INTERVIEWS The research team held interviews with the owners of nine roundabout corridors at which field data was collected for this project. The interviews provide an insight into the creation and history of these roundabout corridors, agency and community goals for the corridors, and their effectivness at meeting those goals. The following were several objectives of performing the interviews: Obtain any corridor specific data for use in the Work Plan. Gain an insight into why roundabouts were chosen for the specific corridor. Obtain any studies of the roundabout corridor applicable to this project as a whole and supplement the literature review. Engage the operators of roundabout corridors and understand what guidance and performance measures would be most useful to them when considering roundabouts for intersection control on an arterial. Interviews with the Maryland State Highway Administration and the City of San Diego were held in person, and interviews with other agencies were conducted over the phone. Two corridors were covered in a single interview with the City of Carmel, Indiana. The interviews reveal a variety of contexts in which roundabout corridors have come into being. Some of the corridors were designed purposefully as a complete corridor; others grew organically over time. The variety of motivations for considering roundabouts, the variety of levels of interaction with the public, and the design treatments ultimately constructed reinforce the notion that each corridor is a unique installation. The CCD developed in this project presents a process that fits well with each of these corridors, primarily because it enables case specific comparisons and evaluations. Summaries of each interview are provided in the following sections. 2.5.1. MD 216 – SCAGGSVILLLE, MD Mike Niederhauser of the Maryland State Highway Administration (SHA), Office of Traffic and Safety, visited KAI’s Baltimore office in November 2011. Mr. Niederhauser has served as SHA’s de facto roundabout coordinator since the construction of Maryland’s first roundabout nearly 20 years ago. He provided the project team with background information on the MD 216 roundabout corridor. One team member participated in person and another participated via video conference. MD 216 was not envisioned by SHA as a roundabout corridor, but rather developed into one over time as roundabouts were added in proximity to other roundabouts. Planning for the US 29/MD 216 interchange began in the mid 1990s. The two roads met at an at grade, signalized intersection at the time, and SHA was converting US 29 into an expressway as well as widening and relocating MD 216 between US 29 and I 95. The state considered a number of interchange forms and ramp terminal control options, and, ultimately, selected

Evaluating the Performance of Corridors with Roundabouts Page 2-22 Chapter 2–Research Approach two lane roundabouts for the two ramp terminal intersections. SHA believed roundabouts offered a number of benefits, including reduced delay, and traffic forecasts indicated two lane roundabouts would sufficiently serve future demand. SHA and their consultants used SIDRA to analyze traffic operations. These two roundabouts, as well as the others described below, were primarily analyzed in isolation and not as part of a series. After the opening of the interchange in 2001, two roundabouts to the west were constructed to accommodate private developments. The first of these roundabouts was an intersection with a new road, Maple Lawn Boulevard. The developers of Maple Lawn initially considered a signalized intersection, but analysis indicated queues from the signal would spill back into the roundabout. A roundabout was not projected to have queue spillback issues and was ultimately selected for the intersection. The MD 216/Maple Lawn Boulevard roundabout opened around 2004. The final roundabout on the corridor, at MD 216/Old Columbia Pike, opened in 2009. This intersection was initially two way stop controlled and improvements were required due to development. A roundabout was selected for a number of reasons including operational performance. According to the SHA, the public and other stakeholders have generally had a positive reaction to the roundabouts, both initially and as others have been added to the corridor. 2.5.2. LA JOLLA BOULEVARD – SAN DIEGO, CA During the visit to La Jolla Boulevard, one member of the research team met with Siavash Pazargadi, a Senior Traffic Engineer with the City of San Diego. Mr. Pazargadi discussed the history of the La Jolla Boulevard corridor and provided the team with several of the studies that led to the implementation of a road diet and the roundabouts. The La Jolla Boulevard corridor is located within a neighborhood business district surrounded by residential areas. Before constructing the roundabouts, La Jolla Boulevard was a five lane cross section with parallel parking. One of the five intersections ultimately converted to roundabouts was originally a signal (at Bird Rock Avenue), and one was originally an all way stop controlled intersection (at Forward Street). The remaining intersections were two way stop controlled. The corridor serves an average daily traffic volume of 22,000 to 23,000 vehicles per day. In the late 1990s, there was considerable interest by the community to slow down traffic. Businesses in the corridor had high turnover and were unable to aract customers compared to other business districts in the area. Speeds along La Jolla Boulevard were in the range of 35 to 40 mph, which made the corridor less comfortable for bicyclists and pedestrians. The community groups in the area are among the most active in the San Diego area. An early proposal was to reduce a travel lane in each direction and add diagonal parking. However, four lanes would be needed at the all way stop controlled intersection at Forward Street. In

Evaluating the Performance of Corridors with Roundabouts Chapter 2–Research Approach Page 2-23 addition, neighborhood groups were concerned over the potential for diversion of traffic into adjacent neighborhoods. The City of San Diego engaged Dan Burden to conduct some design charees to explore ways to enhance the corridor, and Michael Wallwork provided concept designs for roundabouts at each of the key intersections. The roundabout analysis conducted in SIDRA suggested that the single lane roundabouts could accommodate approximately 27,000 vehicles per day, thus allowing a three lane cross section to be implemented. To reduce the likelihood of diversions to adjacent streets, a number of traffic calming measures were introduced, including neighborhood traffic circles; later data collection proved the measures were effective. The corridor transformation was implemented over a period of seven years. The City tried to use as many existing street features as possible to minimize right of way acquisition, and the project was coordinated with other utility work (the water mains were replaced simultaneously). The two roundabouts on the south end were built by a developer of an adjacent 139 unit condominium complex in 2005–2006; the remaining roundabouts were built in 2007–2008. Each roundabout had a construction cost of approximately $800,000 to $900,000. For those parts not funded by the developer, funding came from the San Diego Association of Governments (SANDAG), the City’s Capital Improvement Program (CIP), and a community development impact fee. A maintenance assessment district was established to pay for landscaping, with the whole community contributing based on distance from the corridor. Public opinion within the corridor has generally been positive. Approximately 10 to 15 percent of the residents expressed no opinion throughout the project. The City has received no complaints and has operated under the principle that no news is good news. There have been occasional comments in the local paper. The businesses have expressed support for the roundabouts since their implementation, although the local economy has not been kind in recent years. The most important lesson learned from this corridor is the need for coordination from beginning to end. Mr. Pazargadi served in this role throughout as the project passed from planning to design engineering to construction engineering. The compartmentalization that occurs in large organizations like the City of San Diego can make it difficult for a project of this magnitude to succeed as originally envisioned. Seamless coordination from a project champion and trust based relationships throughout the project with the community and the city council helped in achieving success. A few of the other lessons learned include the following: In pavement flashers were used at crosswalks throughout the project. A less expensive brand used in the south end has had durability problems, but newer units installed on the northern end have been more reliable. The in pavement flashers use pedestrian push buons for activation; a passive pedestrian detection system was desired but never implemented. Pedestrian crosswalk signals were considered but rejected due to cone of vision challenges.

Evaluating the Performance of Corridors with Roundabouts Page 2-24 Chapter 2–Research Approach A project like this has constant challenges. “If you think the project is good, stick with it.” A toolbox with factual statistics is helpful in communication, particularly when discussing issues related to pedestrian, bicyclist, and elderly issues. The proof of a successful project is in its implementation and use by the community. “If you do a good job, people will want you to do more.” 2.5.3. CITY OF CARMEL, IN Two members of the project team held a conference call with Mike McBride, City Engineer with the City of Carmel, Indiana. Both the Spring Mill Road and Old Meridian Street corridors are located within one quarter mile of US 31 in Carmel. The history of both corridors was discussed with the project team during the call. 2.5.3.1. Spring Mill Road Spring Mill Road is part of the county’s one mile grid network. It was once a gravel road and was paved in the middle of the 20th century. In the 1990s, some held the belief the roadway would someday be widened to four lanes, but this expansion was not desired on the City’s part. Spring Mill Road serves as a transitional area between the commercial areas to the east along US 31 and the residential areas to the west; therefore, the City sought to preserve a narrower roadway to maintain consistency with the residential land use. In the early 2000s, most of the intersections on Spring Mill Road were all way stop controlled (AWSC), and some operated poorly. While the City did not conduct a corridor study, it did study congested intersections individually. In 2005, the first roundabout on Spring Mill Road opened at 116th Street. By 2009, the last of the seven roundabouts currently on Spring Mill Road was opened. The City did not consider traffic signals at any of the intersections on Spring Mill Road, as was becoming the case citywide at the time. Eight to ten roundabouts were being constructed each year. Despite early concerns citywide, opposition to roundabouts was decreasing and the mayor was supportive of their construction. On Spring Mill Road, in particular, single lane roundabouts offered greater capacity than signalized intersections with a similar number of lanes. After the AWSC intersections were replaced with roundabouts, volume on Spring Mill Road increased faster than was expected. Mr. McBride believes this may be due to congestion on US 31 and the delay of a planned Indiana DOT (InDOT) improvement project that will convert US 31 to a freeway and remove at grade intersections. In the meantime, drivers use Spring Mill Road to avoid congestion at the signalized intersections on US 31. InDOT now plans to complete the US 31 project in the mid 2010s. In the interim, the City has added lanes at some of the roundabouts on Spring Mill Road to accommodate higher than anticipated turning volumes. The roundabouts were constructed with 150 foot to 160 foot inscribed circle diameters (ICDs) so they could be expanded inward into double lane roundabouts, but to date the City has only added additional lanes on some approaches.

Evaluating the Performance of Corridors with Roundabouts Chapter 2–Research Approach Page 2-25 The City is generally pleased with the Spring Mill Road corridor and would change relatively lile if it were constructed again. Although the traffic forecasts did not accurately reflect near term conditions, they also assumed US 31 improvements would have been in place. This assumption was consistent with the State’s plans when the forecasts were created. 2.5.3.2. Old Meridian Street Old Meridian Street is an old alignment of US 31 and is built on an angle across the area’s grid roadway network. Prior to the construction of roundabouts, it was a two lane roadway with a 100 foot right of way (ROW). This wide ROW was typical for old state owned roadways. Most of the intersections that are now roundabouts were AWSC when the roadway was two lanes. In 1998, the State and City developed a plan to widen Old Meridian Street to a five lane section with signalized intersections. However, Carmel had recently constructed two roundabouts on Hazel Dell Parkway, and the mayor supported constructing roundabouts on Old Meridian Street as well. The City’s long term vision is to transform the Old Meridian Street corridor into an urban area with high density, mixed use development. To help facilitate this change, the City widened the roadway to four lanes and constructed four roundabouts. Federal funds were used for these improvements, which required InDOT’s review and approval of the plans. InDOT preferred for the roundabouts to be relatively large to accommodate trucks. As a result, they were built with an ICD of approximately 200 feet, which is larger than the City of Carmel prefers. A signal was kept at Old Meridian Street/Carmel Drive because sufficient ROW for a roundabout was not available. The City would make several changes to this corridor if it were constructed again, including using an offset left design for entries and purchasing ROW so approaches were more perpendicular to one another, as well as reducing the size of the ICDs. The roundabouts were completed in 2006. Development has occurred slowly. This is aributed, in part, to the overall slow economy nationwide. The corridor is currently lined with a mix of residential and commercial development, much of which pre dates the roundabouts. In the future, the following changes are foreseen along the corridor: Old Meridian Street/Main Street: Volumes will increase at this intersection because an interchange will be constructed at US 31/Main Street (currently a right in, right out configuration). Old Meridian Street/Grand Boulevard: A fourth leg will be added to this roundabout, and Grand Boulevard will be extended to the east. Grand Boulevard is a master planned roadway, and this roundabout is envisioned as the center of an art and design district along Old Meridian Street.

Evaluating the Performance of Corridors with Roundabouts Page 2-26 Chapter 2–Research Approach Old Meridian Street/Carmel Drive: Volumes will likely decrease at this intersection because the signal at US 31/Carmel Drive will be replaced with an overpass (without an interchange). 2.5.3.3. Analysis Methods and Summary From a traffic operations perspective, the City of Carmel has generally studied roundabouts in isolation, even if multiple roundabouts were being studied on the same corridor simultaneously. Early on, the City used RODEL for operations analyses but later changed to SIDRA. The City tended to tweak early roundabout designs more than they do now and, in general, believes roundabouts should remain single lane as long as possible because well designed single lane roundabouts with ICDs in the range of 150 feet to 160 feet provide greater capacity than single lane roundabouts with poor designs or smaller ICDs. Of the two corridors studied by the project team, the Spring Mill Road project is thought to be more similar to projects communities typically face. Old Meridian Street was somewhat of a unique project because of the extent of ROW available to the City and the coordination with InDOT. 2.5.4. BORGEN BOULEVARD – GIG HARBOR, WA A member of the project team held a conference call with Marcos McGraw, a Project Engineer with the City of Gig Harbor, Washington. Mr. McGraw shared the history of the Borgen Boulevard corridor. Borgen Boulevard was constructed in the 1990s by developers who wanted to create access to land in the area. The project included a new diamond interchange on SR 16, an existing expressway. An existing street—Burnham Drive—was already in place at the location where the northbound ramps were to tie into Borgen Boulevard. The City considered constructing a five leg, signalized intersection at this location to accommodate both facilities, but eventually determined it would be expensive to construct and would operate inefficiently. The City also studied a roundabout for this intersection and determined it would be a more desirable solution than a traffic signal. As a result, the City directed the developers building Borgen Boulevard to build a roundabout at the Borgen Boulevard/SR 16 northbound ramps/Burnham Drive intersection. Once Borgen Boulevard was built, development began to occur on adjacent land and developers began to construct new intersections. With the Borgen Boulevard/SR 16 northbound ramps/Burnham Drive roundabout in place and operating well, developers expressed a preference for roundabouts rather than traffic signals at these new intersections. The Washington State Department of Transportation (WSDOT) was also promoting the use of roundabouts at the time. For these reasons, roundabouts were added to the Borgen Boulevard corridor as additional intersections were needed. The City’s experience with the roundabouts has generally been positive. City staff members believe the roundabouts on Borgen Boulevard have fewer maintenance needs than traffic signals, and they are able to process about ten percent more traffic volume than traffic signals would. The City has had a few

Evaluating the Performance of Corridors with Roundabouts Chapter 2–Research Approach Page 2-27 issues with large trucks off tracking over curbs at the 112th Street/Peacock Hill Avenue roundabout. This roundabout is smaller than others on the corridor, and was built in a location with ROW constraints. 2.5.5. SR 539 – WHATCOM COUNTY, WA Two members of the project team held a conference call with several individuals from the WSDOT involved in the development of the SR 539 roundabout corridor. The individuals were: Brian Walsh, State Traffic Design and Operations Engineer Dina Swires, Mt. Baker Area Traffic Engineer (also a member of the 03 100 project panel) Dustin Terpening, Communications WSDOT staff explained that the history of the SR 539 corridor began in 2004. This roadway is locally known as the “Guide Meridian” or simply “The Guide.” SR 539 serves as a freight mobility route between I 5 and Canada. In 2004, funds were appropriated for capital improvements to the SR 539 corridor. At the time, SR 539 was a two lane roadway experiencing safety issues related to access points, a high percentage of truck traffic, and head on collisions. The Whatcom County sheriff and local elected officials supported WSDOT’s efforts to improve safety in the corridor. The roadway had daily traffic volumes that WSDOT considered high for a two lane roadway, and in previous years they had considered upgrading the corridor to a freeway. There were strong feelings in WSDOT that improvements to SR 539 should include a cable median barrier on a six mile segment of the roadway, with few breaks in the median. These desires led WSDOT staff to explore corridor and intersection treatments that would facilitate U turns at select locations. WSDOT staff concluded it would be desirable to create a U turn opportunity every mile along the corridor. This provided a balance between the predominantly through traffic on the corridor and the low volume residential and agricultural accesses. With one mile spacing between U turn points, a trip to or from a right in, right out driveway would require no more than one additional mile of trip length. WSDOT first considered jughandles to facilitate U turns but encountered several challenges. Jughandles would have impacted property near intersections, and some would have been unsignalized. Signal warrants were not met at some intersections, including Wiser Lake Road. Furthermore, the District traffic engineer was strongly opposed to signals on high speed roadways and encouraged project planners to find other solutions. WSDOT staff then studied roundabouts on the corridor. Traffic operations at proposed roundabouts were analyzed with SIDRA, and traffic operations at the existing signal at SR 539/SR 544 were analyzed with SYNCHRO. Analyses indicated that two lane roundabouts would operate acceptably on the corridor. A Paramics simulation model was used for visualization purposes, and engineers determined there would be no interaction between successive

Evaluating the Performance of Corridors with Roundabouts Page 2-28 Chapter 2–Research Approach roundabouts. Staff indicated they would likely use simulation for visualization purposes today, although likely VISSIM rather than Paramics. WSDOT staff actively communicated with stakeholders and the public throughout the project, particularly after roundabouts were selected for the corridor. WSDOT conducted strategic, in person engagement with local elected officials, the media, local trucking companies, and the fire department. A model of a roundabout was created in a parking lot, and interested parties were able to drive through it so they might be€er understand how their vehicles would be accommodated. Open house meetings, a blog, and a Whatcom County newsle€er were used to keep the general public informed. Mr. Terpening stated communicating with the key people in key organizations was essential to the project’s success. The roundabouts and widened roadway opened in July 2010, and WSDOT perceives the project as a great success. Nearly all respondents to an online poll are supportive of the roundabouts, whereas approximately 30 percent of those surveyed were opposed to the roundabouts prior to their construction. Mr. Terpening stated that, two years after opening, he still receives emails from the public expressing gratitude for the roundabouts. Some individuals also request that other roadways in the area be converted to roundabout corridors. The study of the corridor is ongoing, and the Insurance Institute for Highway Safety is working on a before/after study. Travel time on the corridor has decreased. Truck drivers traveling between the US and Canada timed their trips before and after corridor improvements. Some have reported that a trip between Bellingham and Linden previously took 30 minutes, but now takes 10 to 15 minutes. Corridor residents whose travel pa€erns were impacted by the cable median generally remain supportive as well, and feel the capacity and safety improvements make it worth the time to replace left turn movements with right turn/U turn movements. One year before the roundabouts opened on SR 539, another four lane section of SR 539 with traffic signals and TWSC opened between 10 Mile Road (the southernmost roundabout) and Horton Road. Planning efforts for the widening of this southern section of SR 539 began several years prior to planning efforts for the northern section with roundabouts. Some members of the public have indicated to WSDOT they prefer the section of the corridor with roundabouts over the section of the corridor with signals, and are frustrated by the need to stop at traffic signals. WSDOT was unable to change the design of the southern portion of the corridor and add roundabouts because the project was too far along by the time roundabouts were selected for the northern half of the corridor. In conclusion, WSDOT staff stated communication was a key to the project’s success. By reaching out to concerned constituents rather than ignoring them, the agency was able to build informed consent for the project. WSDOT staff members believe intersections are “traffic safety and operations decisions” and traffic engineers need to effectively communicate the benefits they offer; this was done on the SR 539 project. Finally, the combination of the cable median barrier

Evaluating the Performance of Corridors with Roundabouts Chapter 2–Research Approach Page 2-29 and the roundabouts was a more effective strategy for the corridor than either would have been by itself, and WSDOT hopes to use these techniques in combination again. The District remains opposed to traffic signals on high speed roadways; the public is pleased with the performance of SR 539 and supportive of roundabouts on high speed roadways. WSDOT is currently planning another roundabout corridor nearby on SR 20. WSDOT offered information on several other lessons learned from the project: The contractor constructed 4 inch rolled curbs rather than 6 inch rolled curbs that were typical at the time. However, based upon positive feedback from the trucking industry, 4 inch rolled curbs have become the new state standard for roundabouts. Signs were added after opening, instructing drivers not to travel beside trucks in the roundabout. These have also been used elsewhere across the state following their initial use on SR 539. WSDOT is generally pleased with the design of the roundabouts. However, if they had anticipated roundabouts prior to awarding project contracts, they would have sought out a consultant with roundabout experience. WSDOT did not plan for oversize/overweight trucks on this corridor but would do so today based on new policies. The communications plan for this project was so successful that it is now used as a model for other projects. 2.5.6. GOLDEN ROAD – GOLDEN, CO A member of the project team held a conference call with Dan Hartman, Public Works Director with the City of Golden. Mr. Hartman discussed the history of the Golden Road corridor. Additionally, the team reviewed several papers and presentations on the corridor presented by Mr. Hartman and others at conferences. Downtown Golden, including the Coors Brewery and the Colorado School of Mines, lies to the northwest of the corridor. I 70 and Denver lie to the southeast. Prior to the roundabouts, Golden Road was a five lane section with two travel lanes in each direction, a two way left turn lane, and, in some locations, paved shoulders or right turn lanes. The paved cross section was approximately 84 feet. The corridor was lined with suburban development such as fast food restaurants and strip shopping centers, and there were numerous access points. Operating speed was approximately 45 miles per hour. The impetus for corridor improvements began in the mid to late 1990s, with a proposal for a development anchored by a grocery store towards the northwestern end of the corridor. Residents of streets intersecting the corridor were already experiencing delay when turning left and they were concerned this delay would increase as a result of additional traffic from the development. Volumes at these intersections did not meet signal warrants.

Evaluating the Performance of Corridors with Roundabouts Page 2-30 Chapter 2–Research Approach A consultant for the City conducted traffic modeling of two scenarios on the corridor: one with traffic signal improvements and one with roundabouts. Both performed well operationally and were viable. Most aendees of public hearings on the project were skeptical of the roundabouts, but the mayor and city council were supportive. Initial plans for the corridor called for three roundabouts, but a fourth roundabout was added at Golden Road/Utah Street at the request of several businesses on the corridor, including a fast food restaurant. Under pre roundabout conditions, queues formed in the parking lot of the restaurant due to the high delay of the left turn movement out of the parking lot. The restaurant thought it would be preferable to prohibit left turns out of the parking lot and instead have customers turn right onto Golden Road and then make a U turn at the Golden Road/Utah Street roundabout. The first four roundabouts on the Golden Road corridor opened in 1998 and 1999. Five years later, a high school northwest of the four roundabouts was reconstructed and the access road intersection was reconfigured. At a public meeting, 70 percent of aendees preferred a roundabout over a traffic signal. A fifth roundabout was added to the corridor at this location. The City believes the corridor has been a success. There has been a 67 percent reduction in accidents. The corridor experienced approximately ten injury accidents per year prior to the roundabouts, and it experienced two injury accidents in the ten years following construction of the roundabouts. The 85th percentile speed on the corridor was reduced to 26 miles per hour. New businesses invested approximately $7 million in real estate along the corridor, and existing businesses invested approximately $7 million as well. In the future, when the corridor is repaved, the City will likely replace the asphalt in the circulatory roadway with concrete. The asphalt had become rued and required occasional maintenance. The City would change lile about the corridor if constructed again. Some have noted that the mid corridor roundabouts at Utah Street and Lunnonhaus Drive have minimal deflection on Golden Road and an ICD of 105 feet, which is considered small for a multilane roundabout. However, there were ROW limitations when the roundabouts were constructed, and there have been no operational or safety performance concerns; consequently, the City would not change the design of these roundabouts. 2.5.7. AVON ROAD – AVON, CO Justin Hildreth, Town Engineer for the City of Avon, participated in a call with a member of the project team. He provided information on operating conditions and the changes that have taken place on the Avon Road corridor since it opened. Additionally, the project team reviewed an ITE Journal article on the corridor (Ourston & Hall 1997). The Avon Road roundabouts opened in 1997, several years after the roundabouts at the nearby Vail interchange. Three intersections on Avon Road south of I 70 were previously controlled with traffic signals. The project was funded with public funds and a contribution from a local ski resort. Since then, roundabout

Evaluating the Performance of Corridors with Roundabouts Chapter 2–Research Approach Page 2-31 corridors have also been built nearby on William J. Post Boulevard and Edwards Access Road, and a corridor is planned nearby in Eagle, Colorado. All of these corridors include interchanges on I 70. Post Boulevard, which opened in 2002, created a new interchange on I 70. This additional link between the Interstate and Avon reduced traffic volume on Avon Road. In 2005 or 2006, the City removed many signs associated with roundabouts from the corridor. City staff believed there was “sign cluer” on the corridor; i.e., the high number of signs was not helpful to drivers. In 2007, the Avon Road/Benchmark Road roundabout was converted from a “teardrop” design, with no circulatory roadway in front of the south leg, to a conventional roundabout design with a complete circulatory roadway. To the south, Avon Road slopes down from the roundabout and passes under a railroad line. The original designers chose a teardrop design due to safety concerns related to the cross slope of the circulatory roadway in front of the south leg. Over time, the teardrop design created circulation challenges on the corridor, which was the impetus for its reconstruction. There have been no reported safety issues since the modification. The City added pavement markings to the circulatory roadways in accordance with the 2009 Manual on Uniform Traffic Control Devices (MUTCD). Prior to this, there were no pavement markings in the circulatory roadway. Mr. Hildreth believes the pavement markings are not obeyed by drivers, and MUTCD may recommend more marking than is optimal. The corridor currently performs well operationally and congestion only occurs during snow storms or following a crash. The City has some concerns regarding pedestrian safety on the corridor. In the spring of 2012, a police survey of the corridor found most drivers yielded to pedestrians, but in some cases it was difficult for drivers to see pedestrians and crossing areas. The City planned to improve sight distance in these areas later in 2012. When funding becomes available, the City plans to reduce the Beaver Creek Boulevard entries to the Avon Road/Beaver Creek Boulevard roundabout from three lanes to two lanes. The City performed a future conditions traffic analysis, including all planned development for the area, and determined two lane entries would sufficiently serve future capacity needs. One of the goals of the lane removal is to improve pedestrian comfort. If the City were to design the corridor today, it would make several changes: Construct full roundabouts at the I 70 interchange. Potentially decrease the capacity of the corridor; the opening of Post Boulevard has decreased volumes on Avon Road. Use fewer pavement markings in the circulatory roadways. 2.5.8. SR 67 – MALTA, NY One member of the project team held a conference call with several individuals from the New York State Department of Transportation (NYSDOT) involved in

Evaluating the Performance of Corridors with Roundabouts Page 2-32 Chapter 2–Research Approach the development and/or current operation of the SR 67 roundabout corridor. The individuals were: Mark Kennedy, Regional Traffic Engineer, NYSDOT Region 1 James Boni, Assistant to the Regional Director, NYSDOT Region 1 Howard McCulloch, Statewide Roundabout Design Specialist, NYSDOT NYSDOT staff shared the history of the corridor and changes that have taken place since it opened. The SR 67 corridor improvements began as a bridge replacement project. The SR 67 bridge over I 87, the Adirondack Northway, needed to be replaced for structural reasons. At the time, the bridge was three lanes wide. Ramp terminal intersections and three other intersections on SR 67 were signalized. As part of the bridge replacement project, NYSDOT performed a traffic study for conditions 20 years into the future, which is typical for NYSDOT projects involving an interchange. Based upon traffic forecasts, an in house NYSDOT group developed a concept for a single point urban interchange (SPUI) at I 87/SR 67. However, NYSDOT determined the SPUI concept was too expensive and would create queue spillback with the signal at SR 67/Kelch Drive. At the request of the NYSDOT Region 1 Director, the State developed a roundabout concept for the corridor. The project expanded in scope from two roundabouts (at the interchange) to five roundabouts: SR 67/State Farm Boulevard SR 67/I 87 southbound ramps SR 67/I 87 northbound ramps SR 67/Kelch Drive SR 67/US 9 NYSDOT added the additional roundabouts to the project to serve forecasted demand and reduce the likelihood of queue spillback into the interchange roundabouts. When roundabouts were proposed for SR 67, there were no roundabouts in NYSDOT Region 1, and regional traffic engineering staff had concerns about adding the first five roundabouts in the region simultaneously on one corridor. Additionally, the traffic engineers were concerned about the operation of roundabouts in a series. At the time, NYSDOT used RODEL to analyze roundabouts, and results showed no queue spillback. Although NYSDOT believed this sufficiently addressed concerns of roundabouts in a series, NYSDOT also agreed to analyze the corridor with a simulation model and directed a consultant to do so. Paramics software was selected for simulation modeling because it modeled roundabouts in a way that was more similar to RODEL than other microsimulation models such as VISSIM. The simulation did not identify any queue spillback into the adjacent roundabouts, and it was used at public meetings for visualization purposes.

Evaluating the Performance of Corridors with Roundabouts Chapter 2–Research Approach Page 2-33 The mayor of Malta and the public were generally supportive of the concept for roundabouts on SR 67, and Region 1 staff chose to move forward with the roundabout corridor plan. The first five roundabouts opened in 2006 2007. Since then, two roundabouts have been added to the east: Dunning Street/Partridge Drive Dunning Street/Hermes Road/Plains Road Additionally, there are now 14 roundabouts on other roadways within two and a half miles of the SR 67 corridor. Since the corridor opened, the SR 67/US 9 roundabout has experienced a high crash frequency. Many of the crashes are by drivers 30 to 50 years of age and familiar with the corridor. Many crashes are related to a failure to yield by entering drivers or conflicts on exits. NYSDOT believes the fastest path speeds are too high, in part because the roundabout was designed to accommodate side by side trucks. NYSDOT has made several improvements to address the crashes at this roundabout: On SR 67, exits were reduced to one lane with pavement markings, and the left lane of SR 67 entries was changed from through left to left only. Transverse pavement markings were added on the US 9 approaches, but they have not reduced speeds. It was noted that US 9 is designed as a high speed roadway because it was the main north south roadway in the area prior to I 87. Many speed related crashes are on the US 9 approaches. The design of SR 67, including curbs and landscaping, is more effective at reducing speeds. NYSDOT noted the roundabouts at the I 87 interchange have high speed features such as overhead signs and right turn bypasses with dedicated receiving lanes. The roundabout exits on SR 67 taper to one lane to receive the right turn lane from the I 87 off ramps. The public has noted this area is challenging for pedestrians. If constructing the corridor again, NYSDOT would make few changes from a corridor perspective. In terms of individual roundabouts, the following changes would be made: Lower approach speeds; Raise the elevation of the SR 67/Kelch Drive roundabout; and Keep roundabouts single lane when possible, and use nearer term design years (single lane roundabouts are more effective at calming traffic than double lane roundabouts). In closing, it was noted that it would be useful to have research on driver wayfinding in roundabout corridors. Some drivers report “gešing lost” on SR 67 and missing a turn because they were unsure at which roundabout they were located. NYSDOT is considering adding sculptures or other unique decorations to the roundabouts to assist with wayfinding.

Evaluating the Performance of Corridors with Roundabouts Page 2-34 Chapter 2–Research Approach 2.6. CONCLUSION The research team prepared a CCD to aid practitioners with objective and comprehensive comparisons of corridor alternatives. To investigate traffic operations on roundabout corridors, the research team identified 58 roundabout corridors in the United States. Nine corridors, representing a diversity of conditions, were selected for data collection. After two “pilot” data collection trips, the research team modified the data collection procedure based on lessons learned. The revised procedure was employed at the remaining seven data collection corridors. The research team also interviewed the owners of the nine study corridors. Several themes emerged: Once several roundabouts are built on a corridor, new or upgraded intersections are more likely to be roundabouts than signalized intersections. Reasons for this include good performance of the roundabouts in place, increased public and agency awareness and acceptance of roundabouts, concerns about queue spillback from signals into roundabouts, access management, and consistency within the corridor. Traffic analysis of roundabout corridors prior to their construction was typically conducted by analyzing each roundabout in isolation. However, several corridors were analyzed with microsimulation. It is anticipated the predictive tools for operational performance developed in this project, combined with the new tools in the HCM 2010, will provide practitioners with a simpler alternative to microsimulation. The safety effect of each corridor was not studied in detail in this project. However, owners of two roundabout corridors constructed as retrofits stated crash frequency decreased on the corridor following the construction of roundabouts. The consistent safety findings reported elsewhere suggest this trend is likely to continue in a corridor context. An agency champion was often the key to a corridor being constructed with roundabouts. The CCD developed for this project appears to be flexible and adaptable to conditions similar to those described in the interviews.

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TRB’s National Cooperative Highway Research Program (NCHRP) Report 772: Evaluating the Performance of Corridors with Roundabouts provides measurement and evaluation methods for comparing the performance of a corridor with a functionally interdependent series of roundabouts to a corridor with signalized intersections in order to arrive at a design solution.

For the purposes of this research, a “series of roundabouts” is defined as at least three roundabouts that function interdependently on an arterial.

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