Lecture 05 Roundabout (Traffic Engineering هندسة المرور & Dr. Usama Shahdah)
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This document summarizes key points from a traffic engineering course lecture on roundabouts. It discusses conflict points, geometric characteristics of roundabouts like entry width and exit width. It covers calculating volumes using passenger car equivalents and peak hour factors. An example is provided on calculating entry, exit, and circulating volumes. Finally, it discusses methods for determining roundabout capacity like the HCM 2000 and Kimber methods, and using software like Synchro to analyze roundabouts.
Lecture 05 Roundabout (Traffic Engineering هندسة المرور & Dr. Usama Shahdah)
- 1. TRAFFIC ENGINEERING COURSE (PWE 8322) ROUNDABOUTS Instructor: Usama Elrawy Shahdah, PhDLecture # 05
- 4. Geometric Characteristics Entry width Inscribed circle diameter Exit width Splitter island width Circulatory roadway width
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- 10. Steps Vehicle Type Passenger Car Equivalent (pce) Car 1.0 Single-unit truck or bus 1.5 Truck with trailer 2.0 Bicycle or motorcycle 0.5 Step 1: Convert trucks and other vehicle types to passenger car equivalents (pce) Step 2: PHF volume adjustment Step 3: Entry volume Step 4: Exit volume Step 5: Circulating volume
- 11. Entry Volume Entry volume = sum of entering turning movements
- 12. Exit Volume Exit volume = sum of turning movements as shown
- 13. Circulating Volume Circulating volume = sum of turning movements as shown
- 14. Example: Volume Conversion Turning movements Roundabout volumes 110 350 140 50 240 100 North/south: 4% SU trucks/buses, 2% combo trucks East/west: 2% SU trucks/ buses ? PHF = 0.94
- 15. Example Step 1: PCE Calculation SB TH: 530 veh (4% SU/bus, 2% combo) % cars (0.94) 1.0 pce/veh = 0.94 % SU/bus (0.04) 1.5 pce/veh = 0.06 % combo (0.02) 2.0 pce/veh = 0.04 fhv = 1.04 530 veh 551 pce Vehicle Type Passenger Car Equivalent (pce) Car 1.0 Single-unit truck or bus 1.5 Truck with trailer 2.0 Bicycle or motorcycle 0.5
- 16. Example Step 1: Completed PCE Calculation Raw Counts PCEs 110 350 140 50 240 100 111 354 141 51 242 101
- 17. Example Step 2: PHF Factor PCEs (hourly) PCEs (peak 15 minutes) 118 377 150 54 258 107111 354 141 51 242 101 141 / 0.94 = 150
- 18. Example Step 3: Calculate Entry Volume Entry volume = sum of entering turning movements 118 377 150 54 258 107 645 ? ? 419 ? 642 797
- 19. Example Step 4: Calculate Exit Volume Exit volume = sum of turning movements as shown 645 ? ? 419 ? 642 797 118 377 150 54 258 107
- 20. Example Step 5: Calculate Circulating Volume Circulating volume = sum of turning movements as shown 645 628 826 419 453 642 797 118 377 150 54 258 107
- 21. Example: Solution Turning movements Roundabout volumes 110 350 140 50 240 100 North/south: 4% SU trucks/buses, 2% combo trucks East/west: 2% SU trucks/ buses 645 628 826 419 453 642 797 PHF = 0.94
- 23. HCM 2000 Method CCCrrriiitttiiicccaaalll gggaaappp (((ssseeeccc))) FFFooollllllooowww---uuuppp TTTiiimmmeee (((ssseeeccc))) UUUppppppeeerrr---bbbooouuunnnddd sssooollluuutttiiiooonnn 444...111 222...666 LLLooowwweeerrr---bbbooouuunnnddd sssooollluuutttiiiooonnn 444...666 333...111 )3600/( )3600/( 1 fc cc tv tv ca e e vc vc va
- 24. HCM method 24
- 25. CONTROL DELAY & LOS 25
- 26. Kimber Method 26 Qe (capacity of entry flow) is linearly dependent upon circulating flow crossing the entry (Qc).
- 27. Kimber Method 27 Factors affecting the capacity of a roundabout: Inscribed circle diameter D (m) width of flare of each entry. e (m), Approach width v (m) effective length over which flare is developed l' (m) entry angle (φ) entry radius (r) (m)
- 28. Kimber Method 28
- 29. Kimber Method 29 Range of geometric variables in data set used by Kimber to develop capacity expression
- 30. Kimber Method (simplified method) 30 Single-lane roundabouts This constraint implies that the capacity of the circulating roadway of the roundabout is 1800 pcph.
- 31. Kimber Method (simplified method) 31 Two lane roundabouts
- 32. Example 32 A single-lane roundabout having the following geometric characteristics: e = 4 m v = 4 m l’= 40 m r = 20 m Φ = 30 degrees D = 40 m circulating volume = 285 pcph the entry leg demand = 315 pcph. Compute the average delay Use an analysis period of 15 minutes.
- 33. Solution 33 Use Simplified Kimber method Delay
- 34. Trafficware Synchro 34 Demonstrated in Class
- 35. Home Reading 35 Synchro Studio 9 User Guide NCHRPREPORT 672 “Design Roundabouts: An Informational Guide”, Second Edition
- 36. 36 Thanks for your time