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From page 121... ... Evaluating the Performance of Corridors with Roundabouts Chapter 4–Applications Page 4-1 CHAPTER 4. APPLICATIONS This chapter presents the two major applications developed under this project: the Corridor Comparison Document (CCD) Read the entire page →
From page 122... ... Evaluating the Performance of Corridors with Roundabouts Page 4-2 Project initiation begins with gaining an understanding of context. What is the roadway location? Read the entire page →
From page 123... ... Evaluating the Performance of Corridors with Roundabouts Chapter 4–Applications Page 4-3 A corridor project driven by community enhancement objectives, speed management needs, or economic development or growth opportunities; and, A hybrid corridor containing roundabouts, traffic signals, and stop controlled intersections. The degree to which the users identifed in Chapter 2 are present also provides practitioners with an understanding of context. Read the entire page →
From page 124... ... Evaluating the Performance of Corridors with Roundabouts Page 4-4 Roadway cross section Right of way Design speed Intersection spacing Alternatives analysis is the third primary stage of the project planning process shown in Exhibit 4 1. Practitioners apply selected performance measures to the developed alternatives, and identify a preferred alternative. Read the entire page →
From page 125... ... Evaluating the Performance of Corridors with Roundabouts Chapter 4–Applications Page 4-5 Exhibit 4-2: Performance Measures Read the entire page →
From page 126... ... Evaluating the Performance of Corridors with Roundabouts Page 4-6 In addition to identifying assessment techniques for performance measures, Chapter 4 of the CCD also notes cost benefit analysis and scoring as two techniques for comparing the results of an alternatives analysis and for identifying a preferred alternative. Chapter 5 of the CCD presents four fictional example applications that illustrate its use: Example Application #1 is a new suburban arterial being built in a greenfield to create access to undeveloped land and to provide increased connectivity. Read the entire page →
From page 127... ... Evaluating the Performance of Corridors with Roundabouts Chapter 4–Applications Page 4-7 for the analysis of roundabouts in an urban street but does not provide a complete set of roundabout specific equations for doing so. The Urban Street Segments chapter refers users to the roundabout control delay equation in Chapter 21 in place of a signal control delay equation. Read the entire page →
From page 128... ... Evaluating the Performance of Corridors with Roundabouts Page 4-8 section of roadway that follows, and ends at the stop bar of a downstream signalized intersection. For reasons discussed in Chapter 3 of this document, this segment definition is problematic. Read the entire page →
From page 129... ... Evaluating the Performance of Corridors with Roundabouts Chapter 4–Applications Page 4-9 Note: After Step L, segments can be aggregated to facility level per HCM 2010 Chapter 16. Exhibit 4-3: Computation Process Step A: Gather Input Data: Sub segment length, posted speed limit, ICD, CID, circulating speed, entering flow, roundabout capacity, restrictive median length, curb length. Read the entire page →
From page 130... ... Evaluating the Performance of Corridors with Roundabouts Page 4-10 First, the analyst gathers input data and FFS is calculated based on the posted speed limit, segment length, central island diameter of the roundabout, and an assumption that overlapping roundabout influence areas (RIA) are not present. Read the entire page →
From page 131... ... Evaluating the Performance of Corridors with Roundabouts Chapter 4–Applications Page 4-11 The RIA models for upstream and downstream sub segments used in Step C are: cfUS SSRIA 1.218.139.165 cfDS SSRIA 5.224.318.149 where RIAUS = upstream roundabout influence area length (feet) ; RIADS = downstream roundabout influence area length (feet) Read the entire page →
From page 132... ... Evaluating the Performance of Corridors with Roundabouts Page 4-12 STEP A: GATHER INPUT DATA Beechmont Avenue is a planned arterial facility. It will have seven roundabouts and no traffic signals. Read the entire page →
From page 133... ... Evaluating the Performance of Corridors with Roundabouts Chapter 4–Applications Page 4-13 where Sf,US = upstream free flow speed (mph) ; Sf,DS = downstream free flow speed (mph) Read the entire page →
From page 134... ... Evaluating the Performance of Corridors with Roundabouts Page 4-14 cfDS SSRIA 5.224.318.149 where RIAUS = upstream roundabout influence area length (feet) ; RIADS = downstream roundabout influence area length (feet) Read the entire page →
From page 135... ... Evaluating the Performance of Corridors with Roundabouts Chapter 4–Applications Page 4-15 sub segment, it is considered to "overlap" and free flow speed is recalculated in the next step. STEP E: RECALCULATE FREE FLOW SPEED OF SEGMENTS WITH OVERLAPPING ROUNDABOUT INFLUENCE AREAS Treating sub segment 7DS with OL = 1, the free flow speed is now 34.9 mph. Read the entire page →
From page 136... ... Evaluating the Performance of Corridors with Roundabouts Page 4-16 associated with the context of the site development, all midsegment access point delays on Beechmont Avenue were assumed to be zero. STEP H: DETERMINE GEOMETRIC DELAY OF EACH SUB SEGMENT Using these controlling free flow speeds, the geometric delay incurred over the roundabout influence area can be estimated for each segment using the following model: cfUSgeom SSDelay 21.011.057.1, fc fDSgeom SS ICDSDelay 1173.009.063.2, where Delaygeom,US = upstream geometric delay (seconds) Read the entire page →
From page 137... ... Evaluating the Performance of Corridors with Roundabouts Chapter 4–Applications Page 4-17 The geometric delay of sub segment 1DS can be calculated using the geometric delay model for a downstream sub segment: s2.4 6.42 1 20 173.0) Read the entire page →
From page 138... ... Evaluating the Performance of Corridors with Roundabouts Page 4-18 The impeded delay of sub segment 1DS can be calculated using the impeded delay model for a downstream sub segment: s5.5) Read the entire page →
From page 139... ... Evaluating the Performance of Corridors with Roundabouts Chapter 4–Applications Page 4-19 Segment Average Travel Time (s) Segment Length (ft) Read the entire page →
From page 140... ... Evaluating the Performance of Corridors with Roundabouts Page 4-20 FACILITY LEVEL OF SERVICE To aggregate the travel times over the entire facility, HCM Chapter 16 is used directly. The facility travel speed is the aggregation of all segment travel speeds. Read the entire page →

From page 121...

... Evaluating the Performance of Corridors with Roundabouts Chapter 4–Applications Page 4-1 CHAPTER 4. APPLICATIONS This chapter presents the two major applications developed under this project: the Corridor Comparison Document (CCD)