Question

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.

Answer 1

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