10 Capacity and LOS Analysis for Freeway (Traffic Engineering هندسة المرور & Prof. Saad AlGadhi)

1. CE 436 Traffic Engineering
Topic 10: Capacity and LOS Analysis for
Freeway (Chapters 13-14)
Prof. Saad AlGadhi
CE 436 –Traffic Engineering
King Saud University
email: salgadhi@ksu.edu.sa

2. in the Fifth edition (2010); 1950, 1965 (LOS), 1985, 2000

4. Table 13.1 Capacity Under Ideal Conditions for Uninterrupted Flow Facilities

6. Table 13.2 Measures of Effectiveness in the HCM2000

7. Figure 13.1 Illustration of Levels of Service and Service Flow Rates

17. PC/km/ln
0- 7
7- 11
11- 16
16- 22
22- 28
> 28

18. Table 14.2: Level of Service Criteria for Basic Freeway Segments and Multilane Highways

19. Figure 14.2 Base Speed-Flow Curves for Freeways

20. Table 14.1 Equations for Curves in Figure 14.1

21. Table 14.3 Maximum Service Flow Rates for Basic Freeway Sections

22. LOS A to C Description
 LOS A describes free-flow operations. Free-flow
speeds prevail. Vehicles are almost completely
unimpeded in their ability to maneuver within the
traffic stream. The average spacing between vehicles
is about 480 ft (146 m.), or 24 car lengths.
 LOS B represents reasonably free flow, and free-
flow speeds are maintained. The lowest average
spacing between vehicles is about 293 ft (90 m.), or
15 car lengths.
 LOS C provides for flow with speeds at or near the
free-flow speed of the freeway. Minimum average
spacings are in the range of 203 ft (62 m.), or 10 car
lengths.

23. LOS D to F Description
 LOS D is the level at which speeds begin to decline slightly
with increasing flows. In this range, density begins to increase
somewhat more quickly with increasing flow. Minimum
average vehicle spacings are about 151 ft (46 m.), or Seven
car lengths.
 At its highest density value, LOS E describes operation at
capacity. Operations at this level are volatile, there being
virtually no usable gaps in the traffic stream. Vehicles are
spaced at approximately 117 ft (36 m.), or six car lengths,
leaving little room to maneuver within the traffic stream.
 LOS F describes breakdowns in vehicular flow. Such
conditions generally exist within queues forming behind
breakdown points.

28. Types of Analysis
1. Operational Analysis (LOS Calculation)
2. Planning Analysis
3. Service Flow Rate/Service Volume analysis:
SFi = MSFi * N * fhv * fp
SVi = SFi * PHF
4. Design Analysis (iterative):
Ni = DDHV/(PHF * MSFi * fhv * fp )

29. Operational Analysis

31. Figure 14.4 Graphic Solution for Speed on a Basic Freeway Segment
Vp=1800
K =1800/62
= 29

32. 1,000

34. Table 14.5 Adjustment to Free-Flow Speed for Lane Width on a Freeway

35. Table 14.6 Adjustment to Free-Flow Speed for Lateral Clearance on a Freeway

36. Total Ramp Density (TRD)

37. Example 14-1 (FFS, p. 295)

38. Table 14.10 Selecting a Speed-Flow Curve in Figures 14.2

46. Table 14.12 Passenger-Car Equivalents for Trucks and Buses on Upgrades

47. Table 14.12 (continued) Passenger-Car Equivalents for Trucks and Buses on Upgrades

48. Table 14.13 Passenger-Car Equivalents for RVs on Upgrades

49. Table 14.14 Passenger-Car Equivalents for Trucks and Buses on Downgrades

50. Example 14-3 (fhv , p. 302)

57. Sample Applications
 FFS: Example 14-1 (p. 295)
 fhv: Example 14-3 (p. 302)
 Op. Analysis: Example 14-4 (p. 303)
 SF/SV: Example 14-6 (p. 306)
 Design: Example 14-7 (p. 308)

58. Example 14-4 (Op. Analysis , p. 303)

59. Figure 14.7 Freeway Segment for Sample Problem 1 (Source: Used with permission of Transportation Research
Board, National Research Council, Highway Capacity Manual, December 2000, Illustration 12-1, p. 12-6.)

60. Figure 14.8 Speed Determination for Sample Problem 14.4

61. Example 14-6 (SF/SV , p. 306)

62. Example 14-6 (SF/SV , p. 306)

63. Example 14-6 (SF/SV , p. 306)

64. Example 14-6 (SF/SV , p. 306)

65. Example 14-6 (SF/SV , p. 306)

66. Table 14.15 Spreadsheet Computation of Service Flow Rates and Service Volumes

67. Example 14-6 (SF/SV , p. 306)

68. Example 14-6 (SF/SV , p. 306)

69. Table 14.16 Levels of Service for Sample Problem
Demand will reach capacity at year

70. Design: Example 14-7 (p. 308)

71. Design: Example 14-7 (p. 308)

72. Design: Example 14-7 (p. 308)

73. Design: Example 14-7 (p. 308)
1,750

74. Design: Example 14-7 (p. 308)
≤ 4

75. Design: Example 14-7 (p. 308)

76. Design: Example 14-7 (p. 308)
1.95
2.22

77. Design: Example 14-7 (p. 308)

78. Design: Example 14-7 (p. 308)

79. Design: Example 14-7 (p. 308)

80. H.W. # 8 Problems
Ch. 14 (p. 314)
1. 14-2
2. 14-4
3. 14-5
4. 14-7
5. 14-8