Background and Summary of a Guide for Roundabouts (2023)

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39 Appendix B: Truck and Bicycle Research CONTENTS DESIGNING FOR TRUCKS RESEARCH .................................................................................. 40 STATE OF THE PRACTICE REVIEW .................................................................................... 41 Background and Definition ................................................................................................... 41 Summary of Guidance ......................................................................................................... 42 TRUCK INDUSTRY OUTREACH ........................................................................................ 45 Outreach Approach .............................................................................................................. 45 Trucking Industry Outreach Summary ................................................................................. 45 DRIVER BEHAVIOR VIDEO DATA COLLECTION ............................................................. 46 Observation Sites ................................................................................................................ 46 Case 2 Summary and Findings ........................................................................................... 48 Case 3 Summary and Findings ........................................................................................... 49 Driver Behavior Summary .................................................................................................... 50 DESIGNING FOR BICYCLES RESEARCH ............................................................................... 51 STATE OF THE PRACTICE REVIEW ................................................................................. 52 Publication Review .............................................................................................................. 52 Agency Review .................................................................................................................... 57 Virtual Field Review ............................................................................................................. 58 TREATMENT CONCEPTS .................................................................................................. 70 REFERENCES .................................................................................................................... 71

40 DESIGNING FOR TRUCKS RESEARCH This summarizes truck research conducted as part of NCHRP Project 03-130. The objective was to assess roundabout design decisions for serving large trucks at multilane roundabouts. In the past decade, a design approach for serving large trucks (WB-62/WB-67 combination tractor- trailers) has emerged. This design approach is defined with three cases that differ in intended truck lane discipline. There is no clear universal definition of each case type, but this research provides the following definitions for subsequent discussion and analysis: ● Case 1 designs may require trucks to encroach into adjacent lanes as they approach, enter, and circulate. ● Case 2 designs accommodate trucks without lane encroachment as they approach and enter the roundabout via a striped/marked gore area that separates adjacent lanes but may require trucks to encroach into an adjacent lane as they circulate the roundabout. ● Case 3 designs accommodate trucks in lane as they approach, enter, circulate, and exit the roundabout. The design approach using truck case types has evolved out of a desire to design for truck movements in three ways. The first is to mitigate capacity reductions caused by trucks at multilane roundabouts by allowing multiple circulating vehicles when trucks are present (rather than all drivers giving way to a truck). The second is to reduce the potential for right-of-way conflicts if trucks encroach over multiple lanes. The third is to provide for side-by-side truck and car movements in locations where such movements are likely or desired. At the same time, creating more space for trucks can increase right-of-way impacts and implementation costs. Larger roundabouts may influence safety performance through higher entry and exit speeds and increased pedestrian crossing distances. For agencies and designers to achieve the desired operational and safety benefits of roundabouts, they must understand if there are operational and/or safety differences among the case types. In other words, it is helpful to know if Case 2 and 3 design decisions support lane discipline and eliminate truck over tracking that may affect safety performance. Human factors are critical, as well: do truck drivers and members of the public understand the various approaches, and can they recognize which type of roundabout they are approaching in time to make the appropriate decision? The truck research included: ● State of the Practice Review ● Truck Industry Outreach ● Driver Behavior Video Review

41 STATE OF THE PRACTICE REVIEW This summarizes the team’s review of select agency guidance for multilane roundabout design for accommodating trucks entering, circulating, and exiting multilane roundabouts—specifically concerning the use of truck cases described above and further defined in the next section. The focus is large combination tractor-trailer trucks (e.g., WB-62/WB-67) rather than single-unit or other smaller trucks. Background and Definition The design community has begun to define multilane roundabouts relative to intended truck lane discipline with three cases. The three case types are not uniformly defined across jurisdictions in terms of the degree of encroachment and design vehicle. The differences among agency definitions and practice are documented in Table 1 and the review of each guidance below. The state of practice review summarizes current agency practice specific to the three cases. The focus is documentation for Cases 2 and 3. The project team outlined design objectives and guidance; agency policies; and any statutes, codes, or laws related to Case 1, 2, and 3 multilane roundabout designs. The project team also contacted each agency to request any additional relevant policies, statutes, codes, or laws as well as any collision history organized by truck case that would allow for a comparison. This review does not attempt to replicate general truck design guidance but focuses on factors and information that could affect or that directly relate to addressing truck lane discipline and the use of truck cases. The project team reviewed relevant information from California, Georgia, Kansas, Maryland, Massachusetts, Oregon, Washington, and Wisconsin, listed below and noted in Table 1. ● Massachusetts Department of Transportation (MassDOT), Guidelines for the Planning and Design of Roundabouts (MassDOT 2020) ● Georgia Department of Transportation (GDOT), Design Policy Manual, Rev. 6.0 (GDOT 2020) ● GDOT, Roundabout Design Guide (GDOT 2019) ● Washington State Department of Transportation (WSDOT), Design Manual (WSDOT 2017) ● California Department of Transportation (Caltrans), Highway Design Manual, Seventh Edition (Caltrans 2017) ● Wisconsin Department of Transportation (WisDOT), Facilities Development Manual (WisDOT 2016) ● Kansas Department of Transportation (KDOT), Kansas Roundabout Guide, Second Edition (KDOT 2014) ● Maryland Department of Transportation (MDOT) State Highway Administration (SHA), Roundabout Design Guidelines (MDOT 2012) ● Oregon Department of Transportation (ODOT), Highway Design Manual (ODOT 2012)

42 Agencies have different multilane design guidance and various documentation to support their approaches. The agency reviews are presented in reverse chronological order based on the most recent date of published guidance reviewed. This document summarizes and compares existing agency guidance for the following aspects: ● Primary design objectives or principles influencing design choices. ● Techniques used for trucks at multilane roundabouts for truck case (Case 1, 2, and 3 guidance). ● Traffic control devices (signs and pavement markings) associated with truck/auto or other conflicts. ● Research or empirical evidence used to support recommendations. The project team also reviewed a 2012 Joint Roundabout Truck Study sponsored by the Wisconsin and Minnesota Departments of Transportation (WisDOT and MnDOT, respectively) that studied and compared truck cases (MnDOT 2012). The findings of that study are shared after the state reviews. Summary of Guidance A summary of state guidance and source documents is provided in Table 1. More detailed information regarding each state’s guidance is provided in subsequent sections. The review findings indicate the increasing prevalence of the use of truck cases over time; older guidance does not use the Case 1, 2, and 3 terminologies. Three of the eight states reviewed (Georgia, Massachusetts, and Wisconsin) provide truck volume thresholds or context descriptions for which certain truck cases are recommended. These thresholds are presented without a documented research basis. The remaining five states emphasize context-sensitivity and do not explicitly discuss truck cases or provide thresholds for their use. There is no universal definition of truck cases and the trucks to which it applies. Each agency also provides a typical design vehicle to be considered. Several states define the design vehicle as a WB-65 truck, which is not defined in the current American Association of State Highway and Transportation Officials (AASHTO) A Policy on Geometric Design of Highways and Streets (Green Book) (AASHTO 2018). Other states define the typical design vehicle to be the WB-67, and many advise that the appropriate design vehicle depends on location and context. Even if a universal definition of the design vehicle pertaining to truck cases was defined, the applicable trucks would vary from agency to agency. Several laws in the surveyed states pertain to trucks at roundabouts: ● Washington (Wash. Rev. Code § 46.61.140 (2021)), Wisconsin (Wis. Stat. § 346.18 (2021)), and Oregon (Or. Rev. Stat. § 811.292 (2022)) have state vehicle code statutes or laws allowing truck drivers to straddle lanes within a roundabout. ● Wisconsin and Oregon law requires drivers to yield to right-of-way to trucks within a roundabout, prohibiting them from driving alongside trucks. Washington law does not include such a provision.

43 Compounding the varying definitions and guidance about case type is the issue of user expectations. There is no uniformly defined approach to convey to drivers which truck case is provided and for which vehicles the design intent applies. Table 1 organizes each state reviewed in reverse chronological order by the most recent date of published roundabout guidance. The table provides a summary of each review; the reviews are presented in more detail below. Table 1: State Guidance on Multilane Roundabout Design with Respect to Truck Presence State Document Name (Year Published) Guidance Massachusetts Department of Transportation (MassDOT) MassDOT Guidelines for the Planning and Design of Roundabouts (MassDOT 2020) ● The guide presents and describes Cases 1 and 2 but does not explain intended truck behavior on exits for the case types. ● The guidance recommends selecting cases based on the truck frequency of each approach: ○ Case 1 is appropriate when trucks comprise <5% of traffic. ○ Case 2 is appropriate when trucks comprise ≥5% of traffic. ● There is no documented basis for the thresholds provided. The guide describes that the truck cases may be provided for select movements and approach legs rather than for the roundabout. ● The typical design vehicle used is a WB-65 but may vary per approach at intersections. Georgia Department of Transportation (GDOT) GDOT Design Policy Manual, Rev. 6.0 (GDOT 2020) GDOT Roundabout Design Guide (GDOT 2019) ● The guidance defines Case 1, 2, and 3 roundabouts based on truck lane discipline entering and circulating. The guidance does not explain intended truck behavior on exits for the truck cases. ● The guidance distinguishes between a Case 2 and Case 2B. Case 2B provides passenger vehicles room to circulate beside trucks, even as trucks may encroach into the adjacent lane. ● The guidance recommends conditions for Case 1 and Case 2 roundabouts based on land use context and truck volume (fewer than 120 trucks per hour for Case 1). There is no documented basis for this threshold. ● The typical design vehicle for Case 1, 2, and 3 is a WB-67 (the design vehicle for all state routes) but may vary based on location and roadway functional classification. Washington State Department of Transportation (WSDOT) WSDOT Design Manual (WSDOT 2017) ● Although the guide does not explicitly discuss truck cases, its guidance provides Case 1 designs for which truck drivers would not maintain lane discipline. ● A 2020 law allows commercial vehicles to straddle lanes in a roundabout if necessary. California Department of Transportation (Caltrans) Caltrans Highway Design Manual (Caltrans 2017) ● The guidance does not explicitly discuss Case 1, Case 2, or Case 3 roundabouts. ● The guidance allows for design vehicle over-tracking and provides design flexibility by considering truck approach percentages. No specific thresholds for truck percentages are provided.

44 State Document Name (Year Published) Guidance Wisconsin Department of Transportation (WisDOT) WisDOT Facilities Development Manual (WisDOT 2016) ● The guide presents and describes Case 1, 2, and 3 design types. The guide states that Case 2 designs may require trucks to encroach on adjacent lanes as they circulate and exit and that Case 3 designs typically allow for left-turning and through trucks to maintain lane discipline while entering and circulating (but that right-turning trucks may encroach as they exit). ● Case 3 design is preferred over Case 1 and Case 2 at intersections that serve 100 or more “large” trucks daily (large is not defined here). The manual acknowledges that where costs or right-of-way impacts are prohibitively expensive or at locations where design truck numbers are very low, other design case types may be more advantageous. ● There is no documented basis for the threshold provided. ● The manual provides tables qualitatively describing the tradeoffs of Case 1, 2, and 3 design elements on operations and safety. ● The standard design vehicle on the state highway system, for which truck cases apply, is a WB-65. ● A 2015 law requires drivers to yield the right-of-way to trucks or other vehicles at least 40 ft long or at least 10 ft wide. ● A comparison of collision data at case types shows higher collision rates normalized by traffic volume at Case 3 sites compared to Case 1 or 2 sites. Kansas Department of Transportation (KDOT) KDOT Kansas Roundabout Guide, Second Edition (KDOT 2014) ● The guide does not explicitly discuss Case 1, Case 2, or Case 3 roundabouts. ● The guide discusses performance tradeoffs of designing for trucks to stay in lane versus over track into adjacent lanes but remains general and provides flexibility in design. Maryland Department of Transportation State Highway Administration (MDOT SHA) Roundabout Design Guidelines (2012) ● The guidance does not explicitly discuss Case 1, Case 2, or Case 3 roundabouts. ● The guidance advises that where truck traffic is “low,” roundabouts may be designed to allow trucks to claim both lanes to navigate through the roundabout. Where truck traffic is “high” (at least 10%), roundabouts may include a wider circulatory roadway width to allow trucks and passenger cars side-by-side. There is no documented basis for the 10% threshold. ● The typical design vehicle is a WB-67. Oregon Department of Transportation (ODOT) ODOT Highway Design Manual (ODOT 2012) ● The manual does not explicitly mention Case 1, 2, or 3 roundabouts but provides examples of accommodating trucks and passenger car vehicles that are side-by-side in entry. The ODOT Highway Design Manual states that a roundabout designer uses a WB-67 as the design vehicle unless coordination with the trucking industry determines that a smaller design vehicle is appropriate. ● Oregon vehicle code (Or. Rev. Stat. § 811.292 (2022)) prohibits passenger car drivers from driving alongside commercial vehicles in multilane roundabouts and allows truck drivers to straddle lanes within a roundabout if necessary.

45 TRUCK INDUSTRY OUTREACH This section summarizes the trucking industry outreach. Outreach Approach The project team conducted outreach to trucking industry organizations nationally and at the local level, conducting interviews with five stakeholders within those organizations. The organizations included the following: ● American Transportation Research Institute (ATRI) ● Specialized Carriers and Rigging Association (SC&RA) ● Oregon Trucking Association (OTA) ● Sage Truck Driving School ● Keen Transport The project team conducted interviews to understand the trucking industry’s collective input on roundabouts, including topics such as: ● The key issues they observe with roundabouts. ● The basis for support or opposition to roundabouts. ● Examples of roundabout design or operations “done well” or noted as having concerns. ● Their understanding of the Case 2 and 3 design intent and relative success. Trucking Industry Outreach Summary A summary of key themes that emerged from the interviews is provided below. ● Driver understanding of and (lack of) familiarity with roundabouts presents a challenge. Several sources noted roundabout training for student drivers is lacking or limited to the classroom setting. Compounding this, turnover in the trucking industry is relatively high, and familiarity with roundabouts among drivers is limited. ● There is a lack of familiarity with Case 1, 2, and 3 designs. Interview subjects were not familiar with the Case 1, 2, or 3 concepts and expressed doubts that drivers can comprehend design intent in real-time without advanced instructional signage. ● Coordination in the roundabout planning stages can achieve mutually agreeable outcomes. Several interview subjects noted a lack of trucking industry input into roundabout design, resulting in roundabouts that are difficult for trucks to navigate. Conversely, coordination can lead to the early identification of intersection needs and may improve outcomes. ● Some design elements create difficulties for operators and can be avoided. Interview subjects advocated for short and/or sloped curbs, removable or thoughtfully placed signage, and the absence of fixed objects in the central island. These design features serve to accommodate truck operations.

46 DRIVER BEHAVIOR VIDEO DATA COLLECTION This section documents the driver behavior video review efforts, including: ● Review existing footage of Case 2 roundabouts for their applicability to this project. ● Set up cameras to observe trucks entering and circulating in Case 3 roundabouts at four sites. The observations pertained only to trucks with 48-ft trailers or longer (i.e., WB-62, WB-65, and WB-67) and do not apply to oversize trucks, overweight trucks, or trucks with multiple trailers. WB-62, WB-65, and WB-67 trucks are the design vehicles the case type approach is intended to serve. The observations inform questions about each design type, such as: ● Are user conflicts exacerbated or mitigated for each design type? ● Is driver behavior consistent across locations and case types? ● Are there other observations that might influence future planning and design decisions? Observation Sites The roundabouts used for Case 2 and Case 3 video observations are listed in Table 2. The case type for each roundabout was initially assessed with a visual review of aerials. Data obtained from WisDOT indicate that the department classifies the selected Wisconsin sites as Case 2. The design of the Fort Worth, Texas, roundabout was confirmed to be Case 2. For the Case 3 sites, the project team confirmed them to be Case 3 with the Arizona Department of Transportation.

47 Table 2: Observation Site Footage Details Intersection City, State Intersection Configuration Date(s) Adjacent Traffic Present1 Number of Observations Case 2 Sites: Existing Footage Riverside/Northern Cross Fort Worth, TX 2x2 3/31/2015 Yes 20 No 6 County Road MM/County Road M Oregon, WI 2x1 10/24/2016 Yes 1 No 2 N Towne Road/County Highway V Deforest, WI 2x1 10/14/2016 Yes 8 No 48 I-94 EB Ramp/County Highway N Cottage Grove, WI 2x1 10/3/2016, 10/4/2016, 10/19/2016 Yes 6 No 11 US 51 NB Ramp/County Highway V Deforest, WI 2x2 10/20/2016 Yes 2 No 19 US 51 SB Ramp/County Highway V Deforest, WI 2x1 10/13/2016 Yes 2 No 3 Case 3 Sites: New Footage State Route 89 / Road 4S State Route 89 / Perkinsville Road Chino Valley, AZ 2x1 10/20/2020 Yes 40 No 38 State Route 260 / Industrial Drive Chino Valley, AZ 2x1 10/21/2020 Yes 54 No 22 State Route 89 / Road 4S State Route 89 / Perkinsville Road Camp Verde, AZ 2x1 10/21/2020 Yes 8 No 24 State Route 260 / Industrial Drive Camp Verde, AZ 2x1 10/22/2020 Yes 38 No 87 1: This variable identifies whether other vehicular traffic is present on the approach with approximately one truck length in front of or behind the truck. This only pertains to conditions when the truck driver is approaching the circulatory roadway and does not include vehicles that the truck driver yields to before entering the circulatory roadway.

48 Case 2 Summary and Findings The Case 2 videos include 128 observations from 6 locations. Of these, 39 observations include the presence of adjacent traffic (i.e., other vehicles in front of, behind, or alongside a truck close enough to reasonably affect the truck driver’s behavior), and 89 observations include no adjacent traffic present.1 Results are discussed based on driver behavior on approach and within the circulatory roadway. The locations are presumed to operate similarly in general, so descriptive trends are aggregated across locations for discussion purposes. Roundabout Approach Truck drivers observed lane discipline on the roundabout approach 61% of the time. They stayed in their lane slightly more frequently in the presence of adjacent traffic versus without adjacent traffic (64% versus 60%). All sites observed higher truck lane discipline in the presence of adjacent traffic. Results should be interpreted with caution, as approximately half the data for the observations with adjacent traffic present come from the site in Fort Worth, Texas, which does not have circulatory striping. This may influence truck drivers’ entry lane discipline. 39% of drivers did not adhere to the design intent (the complement of the 61% total), and that share was relatively unaffected by the presence of adjacent traffic. Even when adjacent traffic was present, 36% of drivers straddled lanes on approach even though the design allows for them to avoid doing so. The results do not support that truck drivers understand how the intersection is intended to be driven when they navigate the roundabout—or even if they do, they did not abide by the intent. There may be factors that correlate truck driver experience or training with lane discipline that cannot be observed in these data; however, the effect is an overall inconsistency in user behavior. Circulatory Roadway Behavior within the circulatory roadway does appear more sensitive to the presence of adjacent traffic than the approach behavior. 47% of drivers (9 of 19) stayed in lane in the presence of adjacent traffic compared to 8% in the absence of adjacent traffic. Regardless of whether truck drivers know how they are meant to drive the roundabouts, they more frequently stayed in their lane with adjacent traffic present than without it. They may be doing so to avoid sideswipe conflicts with adjacent traffic. Overall, 84% of drivers use both lanes and meet the design intent of Case 2. Observations show that 8% of truck drivers stay in their lane with no traffic present. 84% of truck drivers, overall, use both lanes in the circulatory roadway at these sites. No site had a share of drivers observing lane discipline above 24%. Drivers who did maintain lane discipline typically did so by slowing considerably or by using the truck apron. The more common occurrence was for trucks to straddle lanes within the circulatory roadway. 1 The “other traffic present” determination was made separately for approaching and circulating observations.

49 Lane Discipline by Movement Truck driver behavior analyzed for left-turning and through movements was similar to the trends described in the aggregated findings above, with half or more of truck drivers maintaining lane discipline on approach (50 percent for left turns and 63 percent for through movements) and marginal sensitivity to adjacent traffic. In the circulatory roadway, most drivers encroach on adjacent lanes and observe greater sensitivity to the presence of adjacent traffic. Truck Apron Use Of 22 observations where drivers approach in the left lane, 16 drivers (73%) used the truck apron: 9 through truck drivers, 5 left-turning truck drivers, and 2 observed U-turning drivers. Because of the low number of such observations, no trends or conclusions are provided. Case 3 Summary and Findings The Case 3 data collection includes a total of 311 truck observations from 4 locations on State Routes 89 and 260 in Arizona. 140 observations include adjacent traffic at the approach, and 171 observations include no adjacent traffic present. The observation definitions, such as the presence of adjacent traffic, are consistent with those used in the discussion of Case 2 observations. Roundabout Approach Truck drivers overwhelmingly stay in their lane on approach, maintaining lane discipline in 95% of observations. This behavior is not sensitive to the presence of adjacent traffic. The finding is stable across sites. Overall, truck drivers overwhelmingly adhere to the design intent on approach at the Case 3 sites. This finding indicates widespread recognition among truck drivers in these corridors that the roundabout approach lanes and vane islands can accommodate them. Circulatory Roadway 56% of truck drivers do not maintain their lane through the circulatory roadway. Truck driver behavior in the circulatory roadway is more sensitive to the presence of adjacent traffic than it is on the approaches: 53% stay in lane with adjacent traffic compared to 36% without it. Although this observation did not define the degree of encroachment, the majority of these lane encroachments are relatively minor (e.g., the trailing wheels tracking over the lane line by a few feet) and may not impede vehicles traveling the adjacent lane. Fewer than 10% of lane encroachments involved truck drivers appearing to intentionally occupy both lanes through the roundabout. The proportion of trucks staying in their lane with adjacent traffic is consistent across locations, with site observations varying from 47% to 56%. Without adjacent traffic present, lane discipline varied from 21% to 46%. Lane Discipline by Movements Of the 311 observations, 306 were through truck movements along State Routes 89 and 260. Of the 306 through movements, 98% of truck drivers used the right lane.

50 Truck Apron Use The 311 observations included 8 drivers who used the truck apron: 4 through truck drivers in the left lane, 3 left-turning truck drivers, and 1 U-turning driver. Of the 11 truck drivers using the left lane, 6 used the truck apron. Because of the low share and number of such observations, no summary statistics or conclusions are drawn about truck apron usage. Side-by-Side Vehicle Considerations Because the Case 3 design provides for trucks to stay in their lane, it thereby allows passenger vehicles to enter and circulate next to trucks. The data includes 70 instances where passenger car drivers approach the roundabout with an opportunity to travel alongside a truck in the adjacent lane. Only one of these instances involved a truck in the inside lane, whose driver used the truck apron to maintain lane discipline. In 67% of these 70 cases, the passenger car driver enters or continues through the roundabout next to the truck. They generally chose not to do so when they were aligned with or approaching the inside rear corner of the trailer, presenting the driver with a decision to yield or proceed alongside the truck. Truck encroachment does not appear to influence passenger vehicle drivers’ choice to travel adjacent to a truck or to slow down and follow behind it; the truck encroaches on the adjacent lane in approximately 50% of both cases. Passenger vehicle drivers may not be able to discern the truck trailer path in the roundabout when they make their decision to proceed or yield. However, the wide circulatory lanes of the Case 3 roundabouts allow for side-by-side travel even with some truck encroachment on an adjacent passenger car lane. No trucks of any type were observed traveling next to another truck through any roundabout. Driver Behavior Summary The observations indicate the following findings regarding Case 2 and Case 3 video data. These observations relate only to this data and are not intended as a comparison to Case 1 or other Case 2 or 3 operations beyond this data review. Approach Behavior At observed Case 2 sites, approximately two-thirds of truck drivers stay in their lane on the approaches, and the behavior does not appear sensitive to the presence of adjacent traffic. Truck driver behavior is not stable or easily predicted in this small sample. At observed Case 3 sites, 95% of truck drivers stay in their lane compared to 61% for Case 2 roundabouts. Truck driver behavior on approach at observed Case 3 sites does appear stable or predictable. Circulatory Roadway Behavior At observed Case 2 sites, 84% of truck drivers encroach into the adjacent lane in the circulatory roadway. This behavior does appear sensitive to the presence of adjacent traffic; drivers are more likely to stay in their lanes, to the extent afforded by the design, when adjacent traffic is present to avoid sideswipe conflicts. At observed Case 3 sites, most truck drivers (56%) encroach into the adjacent lane, contrary to the design intent. Truck driver lane discipline within the circulatory roadway is approximately

51 16% higher in the presence of adjacent traffic than without it. For Case 3 sites, the majority of observed encroachments were minor and would not have precluded an adjacent passenger vehicle. Side-by-Side Vehicle Considerations The observed Case 3 roundabouts were observed to allow for side-by-side truck and passenger vehicle travel through the circulatory roadway in a manner that cannot be accommodated at Case 1 or some Case 2 designs. About two-thirds of passenger car drivers opted to circulate alongside trucks when they had such an opportunity. DESIGNING FOR BICYCLES RESEARCH The objective of the designing for bicycles research was to identify treatments for integrating bicycles at roundabouts. In the last decade, a significant amount of bicycle-related design material has been released. This includes an increased understanding of the typology of people who bike, the types of facilities that increase comfort levels, and the number of people biking (Dill and McNeil 2012). Figure 1 illustrates the range of typology of people biking. Figure 1: Typology of People Biking In particular, designing for the person who is “interested but concerned” in bicycling has the greatest potential to increase the rate of people biking (Dill and McNeil 2012). While the number of protected bike lane mileage has increased by 600% since 2011, design strategies for intersections, including roundabouts, have remained underdeveloped (NACTO 2019). The designing for bicycles research included the following activities: ● State of the Practice Review ● Develop Treatment Concepts

52 STATE OF THE PRACTICE REVIEW The state of the practice review included material related to designing for bicycles at roundabouts, including design guidance, agency practices, and information from a virtual field review. The review focused on identifying design guidance and practices: ● A review of publications released since 2010 related to bicycle facility design. ● A review of agency policies, guidance, and practices. ● A virtual field review of 10 sites. The following sections summarize the information for the state of the practice review. Publication Review The publication review focused on identifying guidance and research with relevant findings and lessons learned regarding the design of bicycle facilities—particularly at stop-controlled and signalized intersections—that are transferable to roundabout design. The following criteria guided the selection of documents: ● Techniques used for bicycles and pedestrians along urban streets and at signalized and stop-controlled intersections, such as those in FHWA’s Separated Bike Lane Planning and Design Guide (Goodman 2015) and NACTO’s Urban Bikeway Design Guide (NACTO 2014). ● Guidance related to interactions between bicycles and pedestrians with vision disabilities, such as the National Institute on Disability, Independent Living, and Rehabilitation Research’s ongoing Effect of Guidance Surfaces on Travelers with Vision and Mobility Impairments (Bentzen et al. 2021) study, NCHRP Report 834: Crossing Solutions at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision Disabilities: A Guidebook (Schroeder et al. 2016); and TCRP B-46: Tactile Wayfinding in Transportation Settings for Travelers Who Are Blind or Visually Impaired (O’Brien 2021). ● Techniques used for bicycles and integrated pedestrian/bicycle design at roundabouts, including MassDOT’s Separated Bike Lane Planning & Design Guide (Rabito et al. 2015); MassDOT’s Guidelines for the Planning and Design of Roundabouts (MassDOT 2020); and international examples, like the Netherlands’ CROW Design Manual for Bicycle Traffic. (CROW 2017). The review of publications identified: ● Draft design principles. ● Right-turn treatments applicable to roundabout design. ● Guidance related to interactions between people biking and pedestrians with vision disabilities. ● Techniques used for bicycles and integrated pedestrian-bicycle design applicable to roundabouts. The following sections further discuss each of these items.

53 Design Principles The publication review helped identify the following synthesized list of principles related to designing for people biking, specifically people “interested but concerned” in biking. ● Minimize exposure to conflicts. ● Reduce speeds at conflict points. ● Clearly define areas of potential conflict. ● Separate modes. ● Clearly communicate right-of-way priority. ● Provide predictable, simple, direct alignments. ● Provide adequate sight distance. ● Provide comfortable spaces for waiting and decision making. ● Minimize person delay. These nine design principles consistently appeared across the range of reviewed publications, albeit not always with the same terminology or direct identification as a design principle. For instance, the MassDOT Separated Bike Lane Planning & Design Guide (Rabito et al. 2015) identified four principles: ● Minimize exposure to conflicts. ● Reduce speeds at conflict points. ● Communicate right-of-way priority. ● Provide adequate sight distance. Within the explanation for “Minimize exposure to conflicts,” the MassDOT Separated Bike Lane Planning & Design Guide (Rabito et al. 2015) identifies the following treatments: ● Shortening crossing distance with curb extensions. ● Providing two-stage turn queuing areas to allow bicyclists to avoid merging across multiple lanes of traffic during turning movements. ● Providing median refuge areas for two-stage crossings. ● Providing wider street buffers for bicycle queuing and pedestrian storage to shorten crossing distances. While treatments are all applicable under the “minimize exposure to conflicts” design principle, they can also be classified under other design principles found within the MassDOT Separated Bike Lane Planning & Design Guide (although not referred to specifically as a design principle), along with other design documents. (Rabito et al. 2015) For instance, “providing median refuge areas for two-stage crossings” could also be listed under the following design principles: ● Clearly define areas of potential conflict. ● Separate modes. ● Provide predictable, simple, direct alignments. ● Provide comfortable spaces for waiting and decision making.

54 The literature review identified many examples of bicycle design treatments that met multiple draft design principles. However, by reviewing design treatments against the list of draft design principles, the list of design principles was modified to remove and combine principles deemed too similar or not applicable. Right-Turn Treatments Because some aspects of roundabouts are similar to a series of “T” intersections with right turns, the publication review looked at design treatments for bicycle facilities at right turns. The review identified four right-turn treatments applicable to roundabouts designs along with the appropriate draft design principles the treatments meet: ● Tighten turning radius by using the smallest feasible curb radius based on the control vehicle. This is to reduce speeds at conflict points and provide adequate sight distance. ● Recess (set back) crossing to provide adequate sight distance and safe spaces for waiting and decision making. ● Incorporate raised crossing to provide adequate sight distance and safe spaces for waiting and decision making. ● Compound curves for vehicles rather than a single sweeping circular curve to provide adequate sight distance and safe spaces for waiting and decision making. Guidance Related to Interactions between Bicyclists, Pedestrians, and Pedestrians with Vision Disabilities The project team reviewed preliminary findings from ongoing studies along with one relevant publication related to topics about the interactions between people biking, people walking, and people walking with vision disabilities. ● Effect of Guidance Surfaces on Travelers with Vision and Mobility Impairments (Bentzen et al. 2021) ● NCHRP Report 834: Crossing Solutions at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision Disabilities: A Guidebook (Schroeder et al. 2016). The review identified minimal relevant information related to the interaction between bicyclists, pedestrians, and pedestrians with vision disabilities at roundabouts. NCHRP Report 834 directly cites NCHRP Report 672, stating that “Splitter islands should be at least 6 ft or more wide where the crosswalk passes through, allowing storage for a person pushing a stroller, walking a bicycle, or using a wheelchair” (Rodegerdts et al. 2010). NCHRP Report 834 also provides four major types of crosswalk treatments to limit the risk experienced by pedestrians with visual impairments: (1) standard pedestrian signal, (2) pedestrian hybrid beacon (PHB), pedestrian- activated warning devices, such as (3) rectangular rapid flashing beacon (RRFB), and (4) a raised crosswalk (RCW). These treatments are also useful in locations where high vehicle volumes consistently leave few gaps for bicyclists and pedestrians to cross. (Schroeder et al. 2016) A synthesis of the documents identified principles related to designing for pedestrians with vision disabilities, which were consistent with the previously identified draft design principles. The relevant principles and their applications for pedestrians with vision disabilities include:

55 ● Reduce speeds at conflict points, including between people biking and walking. ● Separate modes, including the need to provide a “raised element” between modes that is detectable underfoot and the preference for separated facilities when bike or pedestrian volumes are high enough to regularly require people walking and biking to share the same space. ● Clearly communicate right-of-way priority, including providing clear guidance for pedestrians with vision disabilities about when it is appropriate to cross and how to use auditory cues and markings rather than relying on signage. Also provide mechanisms to allow people with vision disabilities to detect people biking (people biking make little noise) or use design techniques to encourage people biking to yield to people walking. ● Provide predictable, simple, direct alignments, including wayfinding and guidance, like landscaping and underfoot guidance for pedestrians with vision disabilities. ● Provide comfortable spaces for waiting and decision making, including the reduction of excess pavement that may create confusion for pedestrians with vision disabilities. Techniques Used for Bicycles and Integrated Pedestrian/Bicycle Design A review of guidance documents identified techniques used for bicycles and integrated pedestrian/bicycle design applicable at roundabouts. These documents included: A. MassDOT Separated Bike Lane Planning and Design Guide (Rabito et al. 2015) B. MassDOT Guidelines for the Planning and Design of Roundabouts (MassDOT 2020) C. CROW Design Manual for Bicycle Traffic (CROW 2017) D. FHWA Separated Bike Lane Planning and Design Guide (Goodman 2015) Within these documents, techniques applicable to roundabouts were identified and classified within each of the nine draft design principles. The following section is organized according to the draft design principles, with techniques and their relevant source (designated by the letter matching the list above) identified. Techniques from all or multiple sources are designated (ALL) or by multiple letters, respectively. ● Minimize exposure to conflicts. ○ Minimize the number of crossings and length of crosswalks (ALL). ● Reduce speeds at conflict points. ○ Provide raised crosswalks (ALL). ○ The intersection approach geometry area and roundabout radius should provide speed control for vehicles. (B). ● Clearly define areas of potential conflict. ○ A wayfinding buffer provides navigation to pedestrian ramps for those with vision disabilities. The buffer should be distinguishable from the walking area underfoot through texture and color contrast. ○ Stamped asphalt concrete or pavers are not detectably different underfoot from normal walking surfaces. Grass, pebbles, or rough cobblestones are better material choices for landscaping the wayfinding buffer.

56 ○ Transitions between pedestrian, bicycle, buffer zones, and crossings must be clearly identifiable (B). ● Separate modes. ○ Bicycles are always offered the option of traveling through a roundabout as a vehicle (B). Depending on the context, off-street accommodation should also be included. People biking can use a ramp to access either a separated bike lane or a shared-use path. For a separated bike lane, the separation between modes should be clearly defined and maintained through crossings. For a shared-use path, users should be aware of the mixing zone and the speed differential between modes minimized (ALL). ● Clearly communicate right-of-way priority. ○ Consider providing supplemental yield lines at roundabout exits to indicate priority at these crossings (A). However, the Manual on Uniform Traffic Control Devices (MUTCD), Section 3B.16, recommends against the use of yield lines in advance of crosswalks on roundabout approaches (B) (MUTCD 2009). ● Provide predictable, simple, direct alignments. ○ The treatment at the roundabout should match or exceed the bicycle comfort level of the approaches. If there are separated bike lanes on the approach roadway, provide separated bike lanes around the roundabout (B). ○ Signs and markings should be included to appropriately guide and prompt safe behavior through intersections (D). ○ Minimize crossing distances so that bicyclists and pedestrians can cross during small gaps in vehicle traffic (ALL). ● Provide adequate sight distance. ○ People driving vehicles exiting the roundabout and people biking approaching the crossing should be able to clearly see each other through the recognition, decision, and yield/stop zones (A, C) ○ The bicycle crossing should be immediately adjacent to and parallel with the pedestrian crossing, and both should be at the same elevation (A). Channelizing islands are preferred to maintain separation between bicyclists and pedestrians but may be eliminated if different surface materials are used (A). ○ The separated bike lane approach to the bicycle crossing should result in bicyclists arriving at the queuing area at a perpendicular angle to approaching motorists (A). ○ People driving and making turns, particularly in trucks, typically do not have an adequate view of cyclists riding adjacent to the vehicle in traffic (C). Bicycle lanes should not be marked within roundabouts, as they are prohibited by the MUTCD (B). Bicycle lanes should be dropped on the approaches to a roundabout and reintroduced beyond the pedestrian crosswalk on the exits at a distance of at least 50 ft (B) (MUTCD 2009). ○ The at-grade crossing of two-lane exits should be avoided due to obstructed visibility. Designs for which this is necessary are strongly discouraged (C). ● Provide comfortable spaces for waiting and decision making. ○ There should be space for pedestrians and cyclists to comfortably wait and make decisions.

57 ○ Median islands should have a width of at least 6 ft. ○ Detectable warning surfaces should be included on the pedestrian crosswalk to alert pedestrians with visual impairments of the transition into a safe space to wait. ○ Detectable warning surfaces should be included on the separated bike lane median refuge as well for errant people walking. If a width of 6 ft is not possible, detectable warning surfaces should not be included (B). ● Minimize person delay. ○ Slow vehicle operating speeds support yielding behavior (B). Agency Review The agency review focused on identifying examples of existing agency policies, guidance, practices, statutes, codes, and laws regarding designing for bicycles at roundabouts. The review looked at guidance from the following agencies: ● Massachusetts (MassDOT) ● Wisconsin (WisDOT) ● Colorado (CDOT) ● Georgia (GDOT) ● Fort Collins, Colorado ● Bend, Oregon ● Davis, California ● Carmel, Indiana Key findings from the review are shown below: ● The MassDOT Guidelines for the Planning and Design of Roundabouts provides design details regarding designing for bicycles at roundabouts (MassDOT 2020). ● The WisDOT Facilities Development Manual has design details and information about location for bicycle ramps (Section 30.5.13.1) along with the guidance to extend a roundabout side path through the entirety of a series of roundabouts (WisDOT 2016). ● Chapter 19 of the Colorado Department of Transportation (CDOT) Roadway Design Guide includes language surrounding the use of right-turn bypass lanes. In addition, Chapter 14 of the Roadway Design Guide provides design details (CDOT 2018). ● The GDOT Design Manual includes guidance about bicycle accommodations at roundabouts (GDOT 2020). ● No guidance on designing for bicycles at roundabouts was identified from the City of Fort Collins, Colorado. ● The City of Bend, Oregon, put together a bicyclist roundabout brochure, which provides detailed guidance on how to bike through a roundabout as a vehicle. However, the graphic also shows bike ramps. Additionally, the City of Bend Roundabout Evaluation and Design Guidelines published in 2010 provides design details for a bicycle ramp design that accommodates street sweeping in the transition area between the bike lane and ramp

58 (Kittelson & Associates 2010). The City of Bend includes guidance on angles and concrete scoring patterns to help facilitate navigation by pedestrians with vision disabilities to more readily identify bike ramps rather than crosswalk ramps. ● No guidance on designing for bicycles at roundabouts was identified from the City of Davis, California, including bicycle-only roundabouts in the city. The virtual field review includes a bicycle-only roundabout from Davis, California. ● The City of Carmel, Indiana, recently opened roundabouts on S. Ridgeline Road at the intersections of S Rangeline Road/E 126th Street and S Rangeline Road/Executive Drive incorporate a two-way cycle track on the east side of S Rangeline Road across the east approach to both intersections. At both locations, people walking and biking use the same crossing, and the crossings are raised. However, the crossings at the S Rangeline Road/E 126th Street roundabout are multilane. The crossings at the S Rangeline Road/Executive Drive are single-lane. Virtual Field Review The project team conducted a virtual field review that identified the extent to which agencies (within the United States and internationally) are designing for pedestrians and bicycles at roundabouts. The review of each site focused on the compliance of the roundabout with the draft design principles. The virtual field review was conducted at the following locations: ● Eugene, Oregon ● Bend, Oregon ● Lafayette, California ● Davis, California ● Napa, California ● Fort Collins, Colorado ● Carmel, Indiana ● Worcester, Massachusetts ● London, United Kingdom ● York, United Kingdom ● Amstelveen, Netherlands

59 Figure 2: N Terry St, Roosevelt Blvd, Fern Ridge Path—Eugene, OR Design Principle Adherence Minimize exposure to conflicts. The westbound bike lane approach does not provide taper length for neck down and does not include a dashed lane to encourage merging. Reduce speeds at conflict points. Yes. Clearly define areas of potential conflict. Missing detectable warning surfaces and does not provide at least a 2-ft buffer between sidewalk and curb. Separate modes. Yes. Clearly communicate right-of-way priority. Yes. Provide predictable, simple, direct alignments. Yes. Provide adequate sight distance. Yes. Provide comfortable spaces for waiting and decision making. Yes. Minimize person delay. Yes. Source: Google Earth

60 Figure 3: SW Reed Market Road/N Alderwood Circle/Deschutes River Trail—Bend, OR Design Principle Adherence Minimize exposure to conflicts. Yes. Reduce speeds at conflict points. Yes. Clearly define areas of potential conflict. Missing detectable warning surfaces on bike ramps. Separate modes. Yes. Clearly communicate right-of-way priority. Yes. Provide predictable, simple, direct alignments. Yes, although separated bike lanes on approaches are terminated instead of offering a continuous separated bike lane. Provide adequate sight distance. Yes. Provide comfortable spaces for waiting and decision making. Yes. Minimize person delay. Yes. Source: Google Earth

61 Figure 4: Pleasant Hill Road/Olympic Blvd/Olympic Oaks Drive—Lafayette, CA Design Principle Adherence Minimize exposure to conflicts. Channelized right-turn lane might not be necessary. If not required for operations, it creates an additional crossing point for bikes and pedestrians. If necessary, splitting the roundabout entrances into two lanes with a refuge island minimizes exposure to conflicts and provides a comfortable space for waiting and decision making. Reduce speeds at conflict points. Yes. Clearly define areas of potential conflict. Yes. Separate modes. Yes. Clearly communicate right-of-way priority. Yes. Provide predictable, simple, direct alignments. Ramp up does not meet angle recommendations (90 degrees at southbound northwest ramp). The dashed bike lane is >100 ft but would need to go back farther for cyclists to merge over and enter the roundabout (rather than stay in the right channelized lane). Provide adequate sight distance. Yes Provide comfortable spaces for waiting and decision making. Yes Minimize person delay. Yes Source: Google Earth

62 Figure 5: W Quad and Shields Avenue—Davis, CA Design Principle Adherence Minimize exposure to conflicts. Yes. Reduce speeds at conflict points. Yes. Clearly define areas of potential conflict. Missing sidewalk detectable warning surfaces. Separate modes. Yes. Clearly communicate right-of-way priority. There are no yield markings at the entrance; it is not clear that the bicyclist must yield to traffic in the circle when entering. Provide predictable, simple, direct alignments. Yes. Provide adequate sight distance. Yes. Provide comfortable spaces for waiting and decision making. Yes. Minimize person delay. Yes. Source: Google Earth

63 Figure 6: Napa, California (City of Napa) *This set of three roundabouts within close proximity of one another is currently under construction as of August 2020) The review was based on the proposed designs. Design Principle Adherence Minimize exposure to conflicts. Yes. Reduce speeds at conflict points. Yes. Clearly define areas of potential conflict. Appears to be missing tactile warning panels at bike ramps. Separate modes. Yes. Clearly communicate right-of-way priority. Yes. Provide predictable, simple, direct alignments. Yes. Provide adequate sight distance. Yes. Provide comfortable spaces for waiting and decision making. Yes Minimize person delay. Gaps in traffic appear infrequent; vehicle volumes and speeds may merit supplemental treatment to encourage yielding, such as RRFB, PHB, or signal. Source: City of Napa

64 Figure 7: W Vine Drive/N Shields Street—Fort Collins, CO Design Principle Adherence Minimize exposure to conflicts. Yes. Reduce speeds at conflict points. Yes. Clearly define areas of potential conflict. Missing detectable warning surfaces at median refuge islands and bike ramps. Buffer between the sidewalk and the curb is not identifiable to someone with visual impairment. Separate modes. Yes. Clearly communicate right-of-way priority. Yes. Provide predictable, simple, direct alignments. Inconsistent transitions between on- and off-street options for bicycles (sometimes there is a ramp down, other times not). It is unclear when a cyclist is meant to transition back into the roadway. Provide adequate sight distance. Yes. Provide comfortable spaces for waiting and decision making Yes. Minimize person delay. Yes. Source: Google Earth

65 Figure 8: W Main St/Spring Mill Road—Carmel, IN Design Principle Adherence Minimize exposure to conflicts. Yes. Reduce speeds at conflict points. Yes. Clearly define areas of potential conflict. Missing detectable warning surfaces. Separate modes. Yes—all approaches are indicated as shared-use paths. Clearly communicate right-of-way priority. Yes. Provide predictable, simple, direct alignments. Yes. Provide adequate sight distance. Yes. Provide comfortable spaces for waiting and decision making. Yes. Minimize person delay. Yes. Source: Google Earth

66 Figure 9: Worcester Union Station (Front Street/Summer Street/Shrewsbury Street/Grafton Street)—Worcester, MA Design Principle Adherence Minimize exposure to conflicts. Yes. Reduce speeds at conflict points. Yes. Clearly define areas of potential conflict. Yes. Separate modes. No entry or exit ramps for bicyclists to access the sidewalk through the roundabout. Clearly communicate right-of-way priority. Yes. Buffer between the sidewalk and curb does not extend for entire distance between all adjacent crosswalks. Provide predictable, simple, direct alignments. There is no bicycle infrastructure, like signs, lanes, or ramps. Bicyclists approaching the roundabout have to decide, while in motion, when and where to exit and re-enter the roadway. Provide adequate sight distance. Yes. Provide comfortable spaces for waiting and decision making. No entry or exit ramps for bicyclists to access the sidewalk through the roundabout. Minimize person delay. Yes. Source: Google Earth

67 Figure 10: Waterloo Road/A3200 York Road/Stamford Street—London, UK Design Principle Adherence Minimize exposure to conflicts. The roundabout is signalized, which separates some of the merging movements (for instance, bus/bike lane entering in southeast corner has its own signal to enter) and allows bicyclists to maintain visibility and position at the correct lane through the use of bike boxes at signals. Bicyclists must merge across lanes for movements other than a left turn. Reduce speeds at conflict points. Minimal horizontal deflection at entrances. Clearly define areas of potential conflict. Yes. Separate modes. Yes, for pedestrians. Clearly communicate right-of-way priority. Yes. Provide predictable, simple, direct alignments. No pedestrian crossing at the northern leg. Provide adequate sight distance. Yes Provide comfortable spaces for waiting and decision making. Yes, for pedestrians. Minimize person delay. High traffic volumes so signalization likely reduces pedestrian delay Source: Google Earth

68 Figure 11: A1036/Moor Lane—York, UK Design Principle Adherence Minimize exposure to conflicts. Yes. Reduce speeds at conflict points. Yes. Clearly define areas of potential conflict. Yes, except for a missing crosswalk. Separate modes. Yes. Clearly communicate right-of-way priority. Signalization at crossings communicates priority on all but one approach. The unsignalized approach has a “yield to pedestrians” sign but not a marked crosswalk. Provide predictable, simple, direct alignments. Possibly—crossings are set back 100+ ft from the circulatory roadway to accommodate queuing at signals; however, this creates a much longer path for pedestrians and cyclists who need to cross more than one approach. Provide adequate sight distance. Yes. Provide comfortable spaces for waiting and decision making. Yes. Minimize person delay. Yes—signalization creates the necessary gaps for pedestrians and cyclists to cross. Source: Google Earth

69 Figure 12: Rembrandtweg/Saskia van Uylenburgweg/Eleanor Rooseveltlaan— Amstelveen, Netherlands Design Principle Adherence Minimize exposure to conflicts. Yes. Reduce speeds at conflict points. Yes. Clearly define areas of potential conflict. Yes. Separate modes. Yes. Clearly communicate right-of-way priority. Yes. Tactile guidance path provided to direct pedestrians with vision disabilities to crossing locations. Separated bike facility at street level. Provide predictable, simple, direct alignments. Yes. Provide adequate sight distance. Yes. Provide comfortable spaces for waiting and decision making. Yes. Minimize person delay. Yes. Source: Google Earth

70 TREATMENT CONCEPTS The project team developed treatment concepts to demonstrate the latest bicycle facility and pedestrian design techniques for various roundabout scenarios. The treatment concepts are the basis for figures in the Guide. The treatments comprise three different roundabouts forms, with each design shown with five different bicycle facility types. The range of options developed support practitioners to identify the treatment appropriate for their site and then to obtain the guidance necessary to design the treatment. Table 3 summarizes the types of concepts that were developed. Table 3. Treatment Concepts Roundabout Form Bicycle Facility Approaching the Roundabout All Mini-roundabouts/ single-lane roundabouts Shared or no bicycle facilities Mini-roundabouts/ single-lane roundabouts On-street bicycle facilities Mini-roundabouts/ single-lane roundabouts One-way separated bicycle facilities Mini-roundabouts/ single-lane roundabouts Two-way separated bicycle facilities Mini-roundabouts/ single-lane roundabouts Shared-use paths Multilane roundabouts Shared or no bicycle facilities Multilane roundabouts On-street bicycle facilities Multilane roundabouts One-way separated bicycle facilities Multilane roundabouts Two-way separated bicycle facilities Multilane roundabouts Shared-use paths Roundabouts with bypass lanes Shared or no bicycle facilities Roundabouts with bypass lanes On-street bicycle facilities Roundabouts with bypass lanes One-way separated bicycle facilities Roundabouts with bypass lanes Two-way separated bicycle facilities Roundabouts with bypass lanes Shared-use paths

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