Question

In: Civil Engineering

An existing urban freeway with 4 lanes in each direction has the following characteristics: Peak hour...

  1. An existing urban freeway with 4 lanes in each direction has the following characteristics:
    • Peak hour volume (in peak direction) 7,070 veh/hr
    • Trucks: 10%,
    • 2,012 vehicles observed in the peak 15-minute time period
    • Lane width = 11’
    • 4’ right side lateral clearance
    • 1.8 ramps per mile
    • Rolling terrain

Determine the LOS in the peak hour.  Clearly show your results for freeflow speed, demand flow rate, capacity, mean operating speed, and density along with the LOS.

Solutions

Expert Solution

Given data:-

  • Peak hour volume (in peak direction) 7,070 veh/hr
  • Trucks: 10%,
  • 2,012 vehicles observed in the peak 15-minute time period
  • Lane width = 11’
  • 4’ right side lateral clearance
  • 1.8 ramps per mile
  • Rolling terrain

The formula used:-

Free-flow speed(FFS)=

where,= Adjustment of length width.

=Adjustment for right shoulder lateral clearance.

= Total ramp density.

Heavy vehicle adjustment factor,(fHV)=1/(1+PT(ET-1)+PR(ER-1))

PT= Decimal portion of a truck in the traffic stream

PR=Decimal portion of RV's in the traffic stream

ET=Equivalent passenger cars of truck

ER=Equivalent passenger cars of RV's

The flow rate in pc/h/ln for a multilane highway= (vp)= V/(PHFxNxfpxfHV)

where
vp= 15-minute passenger-car equivalent flow rate (pc/h/ln)
V =hourly peak vehicle volume (veh/h) in one direction
N = number of travel lanes in one direction
fp =driver population factor with a range of 0.85 to 1.00. Use 1.00 for commuter
traffic.

Speed(S):-

The density=

Calculation:-

From table 9.1 for lane width=11 ft ,= Adjustment of length width=1.9 mi/hr

Assuming lateral clearance=4 ft

From table 9.2  lateral clearance=4 ft and 4 lane in 1 direction =Adjustment for right shoulder lateral clearance=0.4 mi/hr

Free-flow speed(FFS)= =67.82 mi/hr

Heavy vehicle adjustment factor,(fHV)=1/(1+PT(ET-1)+PR(ER-1))

From table 9.25 for rolling terrain ET=2.5 and ER=2 and assuming 2% RVs

=1/(1+0.10(2.5-1)+0.02(2-1))=0.855

The flow rate in pc/h/ln for a multilane highway= (vp)= V/(PHFxNxfpxfHV)

PHF=(Volume during peak hour)/(4 xVolume during peak 15 min within peak hour)=7070/(4x2012)=0.88

The flow rate in pc/h/ln for a multilane highway= (vp)= 7070/(0.88x4x1.00x0.855)=2349.15 pc/hr/lane

The mean operating Speed(S):-

= 334.14 mi/hr

The density=

= 7.03 pc/mi/lane

Hence from Table 9.33

LOS= A

      

Ally Wells answered 1 year ago
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