1. CEE 320 Spring 2008 Level of Service and Design Traffic Volumes CEE 320 Kelly Pitera

2. CEE 320 Spring 2008 Outline 1.Freeway Segment LOS Determination a.Free-flow speed b.Flow Rate 2.Multilane Highway LOS 3.Design Traffic Volume

3. CEE 320 Spring 2008 Freeway LOS

4. CEE 320 Spring 2008 LOS Calculation Does not consider –Special lanes reserved for a particular type of vehicle (HOV, truck, climbing, etc.) –Extended bridge and tunnel segments –Segments near a toll plaza –Facilities with FFS 75 mi/h –Demand conditions in excess of capacity –Influence of downstream blockages or queuing –Posted speed limit –Extent of police enforcement –Intelligent transportation system features –Capacity-enhancing effects of ramp metering Freeway LOS

5. CEE 320 Spring 2008 Input Geometric Data Measured FFS or BFFS Volume (highest) BFFS Adjustment Lane width Number of lanes Interchange density Lateral clearance Volume Adjustment PHF Number of lanes Driver population Heavy vehicles Compute FFS Compute flow rate Determine S from speed-flow curve Determine LOS Compute density using flow rate and speed Check on speed-flow curve BFFS Input Measured FFS Input Freeway LOS If FFS not known Adjust for temporal variation

6. CEE 320 Spring 2008 Determining FFS Measure FFS in the field –Low to moderate traffic conditions Use a baseline and adjust it (BFFS) FFS=free-flow speed (mph) BFFS=base free-flow speed, 70 mph (urban), 75 mph (rural) f LW =adjustment for lane width (mph) f LC =adjustment for right-shoulder lateral clearance (mph) fNfN =adjustment for number of lanes (mph) f ID =adjustment for interchange density (mph) Freeway LOS

7. CEE 320 Spring 2008 Base conditions for basic freeway segment 12-ft lane widths 6-ft right shoulder 2-ft median lateral clearance Only passenger cars 5 or more lanes in each travel direction 2-mi or greater interchange spacing Level terrain Mostly familiar roadway users

8. CEE 320 Spring 2008 Lane Width Adjustment (f LW ) Base condition (f LW = 0) –Average width of 12 ft. or wider across all lanes –Table 6.3 in text From Highway Capacity Manual, 2000 Freeway LOS

9. CEE 320 Spring 2008 Lateral Clearance Adjustment (f LC ) Base condition (f LC = 0) –6 ft. or greater on right side –2 ft. or greater on the median or left side –Table 6.4 in text From Highway Capacity Manual, 2000 Freeway LOS

10. CEE 320 Spring 2008 Number of Lanes Adjustment (f N ) Base condition (f N = 0) –5 or more lanes in one direction –Do not include HOV lanes –f N = 0 for all rural freeway segments –Table 6.5 in text From Highway Capacity Manual, 2000 Freeway LOS

11. CEE 320 Spring 2008 Interchange Density Adjustment (f ID ) Base condition (f ID = 0) –0.5 interchanges per mile (2-mile spacing) –Interchange defined as having at least one on-ramp –Determined over 6-mile segment –Table 6.6 in text From Highway Capacity Manual, 2000 Freeway LOS

12. CEE 320 Spring 2008 Determining FFS Use a baseline and adjust it (BFFS) FFS=free-flow speed (mph) BFFS=base free-flow speed, 70 mph (urban), 75 mph (rural) f LW =adjustment for lane width (mph) f LC =adjustment for right-shoulder lateral clearance (mph) fNfN =adjustment for number of lanes (mph) f ID =adjustment for interchange density (mph) Freeway LOS

13. CEE 320 Spring 2008 Input Geometric Data Measured FFS or BFFS Volume (highest) BFFS Adjustment Lane width Number of lanes Interchange density Lateral clearance Volume Adjustment PHF Number of lanes Driver population Heavy vehicles Compute FFS Compute flow rate Determine S from speed-flow curve Determine LOS Compute density using flow rate and speed Check on speed-flow curve BFFS Input Measured FFS Input Freeway LOS If FFS not known Adjust for temporal variation

14. CEE 320 Spring 2008 Determining Analysis Flow Rate Adjust hourly volumes to get pc/ln/hr vpvp =15-minute passenger-car equivalent flow rate (pcphpl) V=hourly volume (veh/hr) highest, total one direction PHF=peak hour factor N=number of lanes in one direction f HV =heavy-vehicle adjustment factor fPfP =driver population adjustment factor Freeway LOS

15. CEE 320 Spring 2008 Peak Hour Factor (PHF) Typical values –0.80 to 0.95 –Lower PHF characteristic of rural or off-peak –Higher PHF typical of urban peak-hour V=hourly volume (veh/hr) for hour of analysis V 15 =maximum 15-min. flow rate within hour of analysis 4=Number of 15-min. periods per hour Freeway LOS

16. CEE 320 Spring 2008 Heavy Vehicle Adjustment (f HV ) Base condition (f HV = 1.0) –No heavy vehicles –Heavy vehicle = trucks, buses, RVs Two-step process –Determine passenger-car equivalents (E T, E R ) for this traffic stream –Determine f HV Freeway LOS

17. CEE 320 Spring 2008 Passenger-Car Equivalents (E T, E R ) Extended segments method –Determine the type of terrain and select E T, E R Level, rolling, mountainous –No one grade of 3% or more is longer than 0.25 miles OR –No one grade of less than 3% is longer than 0.5 miles –Table 6.7 in text From Highway Capacity Manual, 2000 Freeway LOS

18. CEE 320 Spring 2008 Passenger-Car Equivalents (E T ) Specific grades method –Any grade of 3% or more that is longer than 0.25 miles OR –Any grade of less than 3% that is longer than 0.5 miles From Highway Capacity Manual, 2000 Freeway LOS

19. From Highway Capacity Manual, 2000 Freeway LOS

20. CEE 320 Spring 2008 Passenger-Car Equivalents (E R ) Freeway LOS

21. CEE 320 Spring 2008 Passenger-Car Equivalents (E T, E R ) Composite grades method –Determines the effect of a series of steep grades in succession –Distance weighted average – Method OK if… All subsection grades are less than 4% OR Total length of composite grade is less than 4000 ft. –Otherwise, use a detailed technique in the Highway Capacity Manual (HCM) From Highway Capacity Manual, 2000 Freeway LOS

22. CEE 320 Spring 2008 Determine f HV f HV =Heavy vehicle adjustment factor E T, E R =Passenger-car equivalents for trucks/buses and RVs P T, P R =Proportion of trucks/buses and RVs in traffic stream Freeway LOS

23. CEE 320 Spring 2008 Driver Population Adjustment (f P ) Base condition (f P = 1.0) –Most drivers are familiar with the route Commuter drivers Typical values between 0.85 and 1.00 –Analyst selects the value using judgement –Dependent on local conditions (scenic views, etc.) Freeway LOS

24. CEE 320 Spring 2008 Determining Analysis Flow Rate Adjust hourly volumes to get pc/ln/hr vpvp =15-minute passenger-car equivalent flow rate (pcphpl) V=hourly volume (veh/hr) highest, total one direction PHF=peak hour factor N=number of lanes in one direction f HV =heavy-vehicle adjustment factor fPfP =driver population adjustment factor Freeway LOS

25. CEE 320 Spring 2008 Input Geometric Data Measured FFS or BFFS Volume (highest) BFFS Adjustment Lane width Number of lanes Interchange density Lateral clearance Volume Adjustment PHF Number of lanes Driver population Heavy vehicles Compute FFS Compute flow rate Determine S from speed-flow curve Determine LOS Compute density using flow rate and speed Check on speed-flow curve BFFS Input Measured FFS Input Freeway LOS If FFS not known Adjust for temporal variation

26. CEE 320 Spring 2008 Define Speed-Flow Curve Select a Speed-Flow curve based on FFS From Highway Capacity Manual, 2000 Freeway LOS

27. CEE 320 Spring 2008 Determine Average PC Speed (S) For 70 < FFS ≤ 75 mph AND (3400 – 30FFS) < v p ≤ 2400 For 55 < FFS ≤ 70 mph AND (3400 – 30FFS) < v p ≤ (1700 + 10FFS) For 55 < FFS ≤ 75 mph AND v p < (3400 – 30FFS) Freeway LOS

28. CEE 320 Spring 2008 Input Geometric Data Measured FFS or BFFS Volume (highest) BFFS Adjustment Lane width Number of lanes Interchange density Lateral clearance Volume Adjustment PHF Number of lanes Driver population Heavy vehicles Compute FFS Compute flow rate Determine S from speed-flow curve Determine LOS Compute density using flow rate and speed Check on speed-flow curve BFFS Input Measured FFS Input Freeway LOS If FFS not known Adjust for temporal variation

29. CEE 320 Spring 2008 Determine Density Calculate density using: D=density (pc/mi/ln) vpvp =flow rate (pc/hr/ln) S=average passenger-car speed (mph) Freeway LOS

30. CEE 320 Spring 2008 LOS Criteria for Basic Freeway Segments From Highway Capacity Manual, 2000 Determine LOS Freeway LOS

31. CEE 320 Spring 2008 Define Speed-Flow Curve Select a Speed-Flow curve based on FFS From Highway Capacity Manual, 2000 Freeway LOS

32. CEE 320 Spring 2008 Example Geometry 11 ft. lane width 2 lanes Left lateral clearance = 5 ft. Right lateral clearance = 4 ft. Other SR 520 7 am PHF = 0.95 2% trucks 3% buses Determine the typical LOS for a 6 mile stretch of roadway with 5 interchanges. Freeway LOS Determine free flow speed, analysis flow rate

33. CEE 320 Spring 2008 Determine FFS (f LW ) FFS = BFFS – f LW – f LC – f N – f ID BFFS is 70 mph for urban freeway Given 11 ft lanes f LW = 1.9 Freeway LOS

34. CEE 320 Spring 2008 Determine FFS (f LC ) Freeway LOS FFS = BFFS – f LW – f LC – f N – f ID Given 2 lanes, 4ft right clr f LC = 1.2

35. CEE 320 Spring 2008 Determine FFS (f N ) FFS = BFFS – f LW – f LC – f N – f ID Given: 2 lanes f N = 4.5 Freeway LOS

36. CEE 320 Spring 2008 Determine FFS (f ID ) In a 6-mile stretch there are 5 interchanges Freeway LOS 5/6=.833 Linear interpolation: (1-.75)/(1-0.833)=(2.5-1.3)/(2.5-x); x = 2.05 FFS = BFFS – f LW – f LC – f N – f ID f ID = 2.1

37. CEE 320 Spring 2008 Determine FFS FFS = BFFS – fLW – fLC – fN – fID FFS = 70 – 1.9 – 1.2 – 4.5 – 2.1 = 60.3 mph

38. CEE 320 Spring 2008 Example Geometry 11 ft. lane width 2 lanes Left lateral clearance = 5 ft. Right lateral clearance = 4 ft. Other SR 520 7 am PHF = 0.95 2% trucks 3% buses Determine the typical LOS the a 6 mile stretch of roadway with 5 interchanges. Freeway LOS FFS = 60.3 mph

39. CEE 320 Spring 2008 At 7am the ½ hour volume is about 4000 veh/hr Assume half in each direction, 4000 veh/hr max Graph from the Puget Sound Regional Council’s Puget Sound Trends, No. T6, July 1997 Determine Flow Rate (V) Freeway LOS

40. CEE 320 Spring 2008 Determine Flow Rate (v p ) E T = 1.5, E R = 1.2 Assume there are no RVs f HV = 1/(1+PT(ET-1) + P R (E R -1) f HV = 1/(1+0.05(1.5-1) + 0(1.2-1) = 0.9756 Assume commuters, therefore f P = 1.00 V p = V/ (PHF*N*f HV *f P ) V p = 4000 vph / (0.95)(2)(0.9756)(1.00) = 2158 pcplph Freeway LOS

41. CEE 320 Spring 2008 Determine LOS Freeway LOS FFS = 60 mph, Vp = 2158 pcplph, S = about 56 mph, Looks like LOS E, Density = 2158/56 = 39 pc/mi/ln

42. CEE 320 Spring 2008 LOS Criteria for Basic Freeway Segments From Highway Capacity Manual, 2000 Freeway LOS

43. CEE 320 Spring 2008 Multilane Highway LOS

44. CEE 320 Spring 2008 Multilane Highway LOS Similar to Freeway LOS A few minor differences Multilane Highway LOS

45. CEE 320 Spring 2008 Free Flow Speed (FFS) Measure FFS in the field –Low to moderate traffic conditions Use a baseline and adjust it (BFFS) FFS=free-flow speed (mph) BFFS=base free-flow speed, 60 mph is typically used f LW =adjustment for lane width (mph) f LC =adjustment for lateral clearance (mph) fMfM =adjustment for median type (mph) fAfA =adjustment for access points (mph) Multilane Highway LOS

46. CEE 320 Spring 2008 Base Conditions for Multilane Highway Level terrain, with grades no greater than 2 percent Minimum lane width = 12 ft Objects no closer than 6 ft from the edge of the traveled pavement (at the roadside or median) No direct access points along the roadway Divided highway Traffic stream composed entirely of passenger cars Free flow speed of 60 mph or more Driver population composed principally of regular users Multilane Highway LOS

47. CEE 320 Spring 2008 Lane Width Adjustment (f LW ) Base condition (f LW = 0) –Average width of 12 ft. or wider across all lanes From Highway Capacity Manual, 2000 Multilane Highway LOS Same as Freeway LOS

48. CEE 320 Spring 2008 Lateral Clearance Adjustment (f LC ) Base condition (f LC = 0) –12 ft or greater TLC LC L = 6 ft for undivided highways –(accounted for in median type adjustment) LC L = 6 ft for two-way left-turn lanes From Highway Capacity Manual, 2000 Multilane Highway LOS

49. CEE 320 Spring 2008 Median Adjustment (f M ) Base condition (f M = 0) –Divided highway From Highway Capacity Manual, 2000 Multilane Highway LOS

50. CEE 320 Spring 2008 Access-Point Density Adjustment (f A ) For each access point/mi FFS decreases by 0.25 mph Base condition (f A = 0) –0 access points per mile For NAPM ≤ 40: f A = 0.25 × NAPM For NAPM > 40: f A = 10 From Highway Capacity Manual, 2000 Multilane Highway LOS

51. CEE 320 Spring 2008 Determining Flow Rate Adjust hourly volumes to get pc/ln/hr vpvp =15-minute passenger-car equivalent flow rate (pcphpl) V=hourly volume (veh/hr) PHF=peak hour factor N=number of lanes in one direction f HV =heavy-vehicle adjustment factor fPfP =driver population adjustment factor Multilane Highway LOS Same as Freeway LOS

52. CEE 320 Spring 2008 Passenger-Car Equivalents (E T ) Extended segments method –Determine the type of terrain and select E T –No one grade of 3% or more is longer than 0.5 miles OR –No one grade of less than 3% is longer than 1 mile From Highway Capacity Manual, 2000 Multilane Highway LOS

53. CEE 320 Spring 2008 Passenger-Car Equivalents (E T ) Specific grades method –Any grade of 3% or more that is longer than 0.5 miles OR –Any grade of less than 3% that is longer than 1 mile From Highway Capacity Manual, 2000 Multilane Highway LOS

54. CEE 320 Spring 2008 Determine Average PC Speed (S) Use v p and FFS curve to find average passenger car speed (S) From Highway Capacity Manual, 2000 Multilane Highway LOS

55. CEE 320 Spring 2008 From Highway Capacity Manual, 2000 LOS Criteria for Multilane Highways Multilane Highway LOS

56. CEE 320 Spring 2008 Design Traffic Volumes

57. CEE 320 Spring 2008 Design Traffic Volumes Need to select the appropriate hourly traffic volume to get the design LOS

58. CEE 320 Spring 2008 Definitions Annual average daily traffic (AADT) –Annual traffic averaged on a daily basis Design hourly volume (DHV) –Traffic volume used for design calculations –Typically between the 10 th and 50 th highest volume hour of the year (30 th highest is most common) K-factor –Relationship between AADT and DHV

59. CEE 320 Spring 2008 Definitions Directional distribution factor (D) –Factor reflecting the proportion of peak-hour traffic traveling in the peak direction –Often there is much more traffic in one direction than the other Directional design-hour volume (DDHV)

60. CEE 320 Spring 2008 Typical Graph Hourly volume as a proportion of AADT Number of hours (annually) with specified or greater volumes 20401006080 0 0.10 0.15 0.14 0.13 0.12 0.11 Highest 100 Hourly Volumes Over a One-Year Period for a Typical Roadway K 30 =0.12

61. CEE 320 Spring 2008 Example Freeway PC only facility AADT = 35,000 veh/day FFS = 70 mph Number of lanes required to provide at least LOS C using the 30 th highest annual hourly volume? Commuters D = 65% (PH traffic in peak dir.) PHF=0.85

62. CEE 320 Spring 2008 Example K = 0.12 (graph) D = 0.65 (given) AADT = 35,000 (given)

63. CEE 320 Spring 2008 Example V = 2730 (previous slide) PHF = 0.85 (given) N = 2 (assume 4-lane freeway) f HV = 1.0 f P = 1.0 From Table 6.1 in text, maximum flow rate for FSS = 70mph and LOS C is 1770 pc/h/lane. 1606 pc/h/lane < 1770 pc/h/lane, therefore 4-lane freeway (2 lanes each direction) is okay.