Capacity Analysis of Basic Freeway Sections Chapter 12 Continued

1
(No Transcript)
2
(No Transcript)
3

• Capacity Analysis of Basic Freeway Sections
  (Chapter 12 Continued)
• Problem 12-1
• 4-lane freeway, rolling terrain, 60mph design
  speed, 11ft lane with obstructions on both sides
  at an average distance2.0 feet
• 10 trucks, 3 RV, and 2 Buses

4

• PHF0.95
• c2,000 pcphpl
• v/c1.00(E), .84(D), .69(C), .49(B)
• N2, fw.91 (table 12-3), fp1.00
• ET4, EB3, ERV3 (table 12-5)
• fHV0.71
• SFB2000(.49)(2)(.91)(1)(.71) 1274 vph

5

• SFc2000(.69)(2)(.91)(1)(.71) 1794 vph
• SFD2000(.84)(2)(.91)(1)(.71) 2184 vph
• SFE2000(1.0)(2)(.91)(1)(.71) 2600 vph
• LOS A is not possible for highways with 60 mph
  design speed

6

• To convert peak 15-minute flows to peak-hour
  flows, multiply by PHF
• SVB(1274)(.95)1210 vph
• SVC(1794)(.95)1704 vph
• SVD(2184)(.95)2075 vph
• SVE(2600)(.95)2470 vph
• Comparing these criteria with given demand
  volumes
• 1,800 vph(D), 2,200 (E), 2,800(F)

7

• Problem 12-2
• Solve the service flow equation for the effective
  v/c ratio
• v/cSF/(c)(N)(fw) (fp) (fHV)
• fHV1/1.1(5-1).71 for upgrade
• fHV1/1.1(1.7-1).93 for level
• v/c4000/(2000)(3)(1) (1) (.71).93 upgrade,
  LOS D
• v/c4000/(2000)(3)(1) (1) (.93).71 Level, LOS
  C

8

• Densities for LOS CD are 2641
• Adjust. needed to reflect trucks
• 26.10(1.7)D.9(1)D1.07D
• D(level)26/1.0724.03 vpmpl
• 41.10(5)D.9(1)D1.4D
• D(upgrade)41/1.429.3 vpmpl
• FSD, S(level)4000/(24.03)(3)55mph
• S(upgrade)4000/(29.3)(3)46mph

9

• Problem 12-3
• The avge. grade tot. rise/tot. run
• Grade Run Rise
• 0.03 2,640 79.2
• 0.05 5,280 264.0
• 0.04 2,640 105.6
• 0.02 2,640 52.8
• 0.03 5,280 158.4
• 0.05 2,640 136.0
• Total 21,120 792.0

10

• Avge. grade(792/21120)1004
• Part b Figure 12-3, at end of composite grade,
  trucks are going at 27 mph,and that is equv. to
  4.9
• part c ET7 (15 trucks, 5 grade of 1.5 miles)
• ERV4 (5 RVs)
• fHV1/1.15(7-1).05(4-1)0.49

11

• Problem 12-4
• Improvement of 4-lane with ideal geometric to a
  6-lane with less than ideal
• c2,000, N2, fw1(ideal), fw.91(3 12ft lanes, 0
  ft clearance), fw.89(3 11ft lanes, 1.5ft
  clear.), fw.86(3 10ft lanes, 3.0ft clear. ),
• ET1.7 EB1.5, fHV0.91, fp1.0

12

• c(exs)2000(1)(2)(1)(1)(.91)3653
• c(12-ft lanes) 4986
• c(11-ft lanes) 4877
• c(10-ft lanes) 4712
• Recommend building the 3 12-ft lanes with no
  clearance. This decision is based on capacity.
  Safety should be considered.

13

• Problem 12-5
• A design application in rural area with high
  truck traffic
• The upgrade composite grade analysis indicated
  that minimum truck speed is reached at the end of
  the 6 grade, 1.5 miles from the beginning of the
  grade

14

• NSF/(c )(v/c)i (fw) (fp) (fHV)
• SF1500/.91667, c2000, v/c.77(C), fw 1, fp
  .9
• ET4, rolling14, upgrade 7, down
• ERV3, rolling 4, upgrade 2, down
• EB3, rolling5.5, upgr. 2.75, down
• fHV-rolling0.54
• fHV-upgrade0.18
• fHV-downgrade0.47

15

• N(rolling)2.2 lanes
• N(upgrade)6.7 lanes
• N(downgrade)2.53 lanes
• To attain LOS C, both rolling and downgrade
  require 3 lanes, while upgrade requires 7
  lanes!!!!
• Truck climbing lane may solve this problem

16

• v/c1667/2000(4)(1)(.9)(.18) 1.28
• This would still result in failure of the upgrade
  section. If N 2 lanes
• v/c1667/2000(5)(1)(.9)(.18) 1.06 still
  failure!
• To reduce the severity of the upgrade lower
  longer grades,or alter traffic mix (is it
  possible?)

17

• Problem 12-6
• Operational analysis problem.
• v/c(4400/.95)/2000(3)(1)(1)(.97) 0.80?LOS(D),
  D30 pcpmpl
• convert density to vpmpl
• 30.05(1.7)D.95(1)D1.04D
• D29 vpmpl ?SF/D S(4400/.95)/(29)(3)53 mph

18

• Problem 12-8
• Special procedure for truck climbing lanes
• determine LOS for truck lane and compare to LOS
  for other lanes(trial and error process)
• Downgrade is treated like level terrain (grade is
  4 or less)
• c(T)2000/ET2000/6333trucks/hr

19

• Facility operate close to capacity, and the truck
  lane will carry 333 trucks/hr during the peak 15
  min.
• Total truck traffic4100(.15)615
• flow rate during peak615/.9683
• remaining trucks in mixed traffic 683-333350
  trucks/hr
• SF-up(4100/.9)-3334223 vph

20

• trucks(352/4223)(100)8
• SF-downgrade4100/.94556 vph
• trucks 15
• v/c-up4223/2000(3)(1)(1)(.69) 1.01
  (barely fails)
• v/c-down4556/2000(3)(1)(1)(.9) .84 (LOS D)