A section of a freeway on rolling terrain has the following properties: design hourly volume = 2500 vph, 10% trucks, 2% RVs, PHF = 0.95, two lanes 12 ft wide each, 5 ft lateral clearance and 8 ramps in every 10 miles. Determine the Level of Service (LOS) of the section according to the Highway Capacity Manual 2010.
Assume Base free flow speed (BFFS) = 70 mph
Lane width = 12 ft
Reduction in speed corresponding to lane width, fLW = 0 mph
Total Lateral Clearance = 5 ft
Reduction in speed corresponding to lateral clearance, fLC = 0.6 mph
Total Ramp Density = 8/10 miles = 0.8 /mile
Reduction in speed corresponding to ramp density, fID = 1.54 mph
Assume no. of lanes = 2
Reduction in speed corresponding to no. of lanes, fN = 4.5 mph
Free Flow Speed (FFS) = BFFS – fLW – fLC – fN – fID = 70 – 0 – 0.6 – 4.5 – 1.54 = 63.36 mph
Peak Flow, V = 2500 veh/hr
Peak-hour factor = 0.95
Trucks = 10%
RVs = 2%
Rolling Terrain
fHV = 1/ (1 + 0.10 (2.5-1) + 0.02 (2.0 -1)) = 1/1.17 = 0.855
fP = 1.0
Peak Flow Rate, Vp = V / (PHV*n*fHV*fP) = 2500/ (0.95 * 2 * 0.855 * 1.0) = 1538.94 ~ 1539 veh/hr/ln
S = FFS
Density = Vp/S = 1539/63.36 = 24.29 veh/mi/ln
Level of service C
Density of LOS C lies between 18 - 25 veh/mi/ln
Get Answers For Free
Most questions answered within 1 hours.