CVE30003 TUTORIAL EXERCISE Roundabout Intersections - Performance Analysis Exercise Analyse the performance of a roundabout with the volumes shown below. Assume no heavy vehicles. Therefore, volumes are in pcu/h. Geometry: · Single lane entries and single lane circulating · Central island diameter 30 m · Circulating road width 5 m · Average width of entering lanes 4 m 50 300 60 JIL 40 600 100 125 JIL 500 25 95 365 50 11 Page 1
Gap acceptance parameters Table 1: Follow up headway (sec), tf Circulating Flow, qc (pcu/h) 20 0 2.81 150 2.76 300 2.70 450 2.65 600 2.59 750 2.53 900 2.48 1050 2.42 1200 2.36 Inscribed Diameter, Di (m) 40 2.51 2.46 2.40 2.35 2.29 2.23 2.18 2.12 2.07 60 80 2.28 2.12 2.23 2.06 2.17 2.01 2.11 1.95 2.06 1.89 2.00 1.84 1.95 1.78 1.89 1.72 1.83 1.67 Table 2: Critical gap (sec), tc Circulating Flow, qc (pcu/h) 20 Inscribed Diameter, Di (m) 40 60 80 0 5.51 150 5.25 300 5.01 450 4.79 600 4.58 750 4.39 900 4.21 1050 4.05 1200 3.90 Table 3: Proportion unbunched, 4 Circulating Flow, qc (pcu/h) 0 150 300 450 600 750 900 1050 1200 4.93 4.47 4.68 4.24 4.46 4.03 4.24 3.83 4.05 3.64 3.87 3.47 3.70 3.31 3.55 3.16 3.40 3.02 Proportion Unbunched (Free), ¢ 1.000 0.833 0.694 0.577 0.476 0.389 0.313 0.688 0.245 0.185 Proportion Bunched, 1 - ¢ 0.00 0.167 0.306 0.423 0.524 0.611 0.755 0.815 4.15 3.93 3.72 3.53 3.35 3.18 3.03 2.88 2.75 Table 4: Average headway between bunched vehicles in the circulating roadway, 4 4 = 2.0 seconds for a single lane roundabout Page 2
Worksheet Approach qe veh/h pcu/h qc pcu/s tf tc ? ? ? s s Q x s veh/h N E S W 3600 = (1 - 0 00 + 0.5 0, 9 0%) 0-0(01- 0) Table 1 Table 2 Table 4 Table 3 or formula I = = (1-0 0%) Number of circulating A lanes 1 2 > 2 0.8 2.2 kd 2 2.2 1 2.2 1-00, 1 - (1-00)00, P = Page 3