Question

In: Civil Engineering

A freeway has the following characteristics: 6 lanes, 3 in each direction 13’ lanes 8’ right...

A freeway has the following characteristics:
- 6 lanes, 3 in each direction
- 13’ lanes
- 8’ right side lateral clearance
- Total of 4 ramps in the 3 miles upstream and 3 miles downstream of the midpoint of the facility
- 2% upgrade for 1.5 miles
- Urban facility with 50% delivery trucks and 50% freight trucks
- 8% trucks
- 3,400 veh/hr in the analysis direction in the peak hour
- 955 vehicles in the peak 15-minute time period

(3) What is the free flow speed of the facility?

(3) What is the passenger car equivalent flow rate?

(3) What is the estimated operating speed of the facility?

(2) What is the density of the facility?

(2) What is the LOS of the facility?

(2) Describe what the LOS indicates about how well the facility is operating?

Expert Solution

Assume, Base free flow speed (BFFS) = 75 mph

Lane width = 13 ft

Reduction in speed corresponding to lane width, fLW = 0 mph

Lateral Clearance = 8 ft

Reduction in speed corresponding to lateral clearance, fLC = 0 mph

Interchanges/Ramps = 4 /6 mile = 0.67 /mile

Reduction in speed corresponding to Interchanges/ramps, fID = 0 mph

No. of lanes = 3

Reduction in speed corresponding to number of lanes, fN = 3 mph

Free Flow Speed (FFS) = BFFS – fLW – fLC – fN – fID = 75 – 0 – 0 – 3 – 0 = 72 mph

Peak hourly volume, V = 3400 veh/hr

Peak 15-min flow = 955

Peak-hour factor = 3400/(4*955) = 0.89

Trucks = 8 %

2% upgrade for 1.5 miles

50 % delivery trucks and 50 % freight trucks

fHV = 1/ (1 + 0.04 (2.5-1) + 0.04 (3.0-1)) = 1/1.14 = 0.877

fP = 1.0

Passenger Car Equivalent Flow Rate, Vp = V / (fHV * PHF*n*fP) = 3400/ (0.877*0.89*3*1.0) = 1452 veh/hr/ln

Estimated operating speed, S = FFS = 59.3 mph

Density = Vp/S = (1452) / (72) = 20.167 veh/mi/ln

LOS C

Density of LOS C should lie between 18 - 26 veh/mi/ln

Facility is operating at freedom to maneuver is noticeably restricted and queues may form behind any significant blockage on the freeway.

Ally Wells answered 11 months ago

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