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Freeways and Multilane Highways. CTC-340. HMWK. Ch 13 Read Section 13.7 Ch 13 # 2, 3 Ch 14# 1, 4, 5, 6, 8. Capacity. HCM2000 definition

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Presentation Transcript
slide2
HMWK
  • Ch 13 Read Section 13.7
  • Ch 13 # 2, 3
  • Ch 14# 1, 4, 5, 6, 8
capacity
Capacity
  • HCM2000 definition
    • The capacity of a facility is the maximum hourly rate at which persons or vehicles can reasonably be expected to traverse a point on a uniform section of a lane or roadway during a given period of time under prevailing roadway, traffic and control conditions
slide4
LOS
  • LOS
    • Table 13-1 MOEs
  • Service Flow
    • Max flow for a given LOS
  • v/c ratio – ratio of flow to capacity of facility
    • Should be <1
    • If v/c > 1 => congestion
freeways
Freeways
  • Pure uninterrupted flow
    • Cars enter and exit via ramps
    • No at grade intersections, driveways etc
  • Based on number of lanes
multilane highways
Multilane Highways
  • Only uninterrupted flow if signals at least 2 miles apart
  • Classified by lanes and median type
  • F 14.1
slide7
LOS
  • MOE is density – pc/ln/mi
  • Capacity = 45pc/ln/mi
    • Freeways
    • multilane hwys => 40 - 45pc/ln/mi
    • F 14.2, 14.3, T 14.1
  • LOS pg 286 - 290
freeway analysis
Freeway Analysis
  • F14.2 & 14.3
  • Operational Analysis
      • How is the existing facility operating
      • vp = V/(PHF*N* fHV * fp ) = pc/hr/ln
      • vp is the demand flow rate under ideal conditions
      • With vp can find FFS from curves F 14.2
      • fp= user population
      • If V = 4600vph, PHF = 0.90, N =3, fHV =0.87, fp = 1
      • What is LOS
      • v= 1958pc/h/ln => LOS =? F 14.2 &3
slide9
Service Flow Rate & Service Vol Analysis
  • SFi = MSFi*N*fHV*fp
    • Can find service flow for each LOS i
      • Use Tables 14.3 or 14.4 to get MSF
slide10
Design Analysis
    • Used to determine # of lanes needed for freeway
    • To determine the number of lanes
    • N = DDHV/(PHF*MSF*fHV*fp)
    • Iterative process
    • Number of lanes depends on design speed
    • Design speed depends on # of lanes
free flow speed freeways
Free Flow Speed - Freeways
  • Free Flow Speed
    • Found when volume < 1000vph/l
    • FFS = BFFS-fLW - fLC – 3.22TRD^0.84
    • fLW – lane width adjustment T14.5
    • fLC – lateral clearance T14.6
      • 6’ on right side 2’ on left
      • Factor only takes right side into account
    • TRD–total ramp density T14.8
      • Total ramps within 3 miles of midpoint of study area/6miles
multilane highways1
Multilane Highways
  • FFS = BFFS-fLW - fLC - fM – fA
  • fLW – lane width adjustment T14.5
  • fLC – lateral clearance T14.7
  • Greatest LC = 6 feet on both sides
      • Undivided Hwys – no median side clearance – taken into account with fM – assume 6’ clearance
      • TWLTL – assume 6’ clearance
      • Divided hwy – based on median, dist to opposing traffic, periodic objects(light poles) never more than 6’
  • fM –median type T 14.8
    • Undivided, TWLTL, divided
  • fID –access points T14.9
    • Driveways or roadways per mile on the right hand side - only include active intersections
multilane highways2
Multilane Highways
  • BFFS – use 60mph if no data available for rural and suburban multilane sites
    • Can estimate speed limit with BFFS
    • 7mph higher than spd limits 40 – 45mph
    • 5mph higher than spd limits 50 – 55mph
example
Example
  • Old 6 lane freeway – 11’ lanes, barriers on right side 2’ from pavement edge, TRD = 3ramps/mile
    • FFS = 75.4- fLW - fLC – 3.22TRD^0.84
    • fLW – lane width adjustment T14.5
    • fLC – lateral clearance T14.6
      • 2’ on right side 6’ on left
      • Factor only takes right side into account
example1
Example
  • Old 6 lane freeway – 11’ lanes, barriers on right side 2’ from pavement edge, TRD = 3 ramps/mile
    • FFS = 75.4- fLW - fLC – 3.22TRD^0.84
    • fLW – 1.9 mph T14.5
    • fLC – 1.6 mph T14.6
    • TRD = 3
  • FFS = 75.4 – 1.9 – 1.6 – 3.22*3^.84= 64.1
example2
Example
  • 4 lane suburban multilane highway – 12’ lanes, barriers on right side 2’ from pavement edge, TWLTL, 30 access points/mile posted spd lmt = 50 mph
    • FFS = BFFS-fLW - fLC - fM – fA
    • fLW – 0.0 mph T14.5
    • fLC – 0.9 mph T14.7 total LC = 6+2 = 8’
    • fM –0.0 mph T 14.8
    • fID –7.5 mph T14.9
  • FFS = 55 – 0 – 0.9 – 0 – 7.5 = 46.6
  • 55 mph 50 + 5 mph for BFFS
heavy vehicle factor
Heavy Vehicle Factor
  • Heavy Vehicle = any vehicle with more than 4 tires
    • Trucks and buses
      • Have similar characteristics
      • Based on a typical mix of trucks
      • 150#/hp
    • RVs
      • Privately owned, self contained or pulled
      • 75 -100 #/hp
passenger car equivalents
Passenger Car Equivalents
  • # of cars displaced by the heavy vehicle
  • ET = PCE for trucks and buses
  • ER = PCE for RVs
  • Increases volume to account for HVs
  • EX: 1000 vehicles 10% trucks, 2% RV
    • ET = 2.5 ER = 2.0
slide19
1000 * 0.1*2.5 = 250pce/hr
  • 1000*0.02*2 = 40 pce/hr
  • 1000*0.88 = 880 pce/hr
  • Total pce = 1170 pce/hr
    • Traffic stream acts like it has 1170 vph on it
    • fHV = vph/(pce/hr) always <= 1.0
    • fHV = 1000/1170 = 0.85
slide20
fHV = 1/(1+PT(ET – 1) +PR(ER – 1))
  • Extended Freeway & Multilane Sections
    • Long section = single section where no grade of 3% or greater is longer than 0.25 miles and if no grade of less than 3% is longer than 0.5 miles
terrain
Terrain
  • Level terrain – short grades less than 2%
    • HVs can maintain same speed as cars
  • Rolling terrain - HV speed substantially below pc speeds but do not get to crawl speed for extended periods
  • Mountainous terrain – HV operate at crawl speed for extended periods or frequently
    • Rare
    • T14.11
specific grades
Specific Grades
  • Any grade <3% longer than 0.5 miles or >3% and longer than 0.25 mile is a specific grade
  • T14.12, T14.13
  • Trucks on Downgrades T14.14
    • RVs same as level sections
composite grades
Composite Grades
  • Series of grades
    • Want to get the equivalent uniform grade for pce
    • Average grade technique
      • Find total rise divide by total run
      • Good when all grades <4% and < 4000ft length
    • Composite grade technique
      • Use truck performance curves to determine equivalent length of grade
driver population factor
Driver Population factor
  • Based on the number of drivers not familiar with the road.
    • Range from 1 – 0.85
    • Usually use 1 unless a field study has been done or it is a highly recreational area
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