Answer:
Assume Base free flow speed (BFFS) = 70 mph
Lane width = 10 ft
Reduction in speed corresponding to lane width, fLW = 6.6 mph
Lateral Clearance = 4 ft
Reduction in speed corresponding to lateral clearance, fLC = 0.8 mph
Interchanges/Ramps = 9/ 6 miles = 1.5 /mile
Reduction in speed corresponding to Interchanges/ramps, fID = 5 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 = 70 – 6.6 – 0.8 – 3 – 5 = 54.6 mph
Peak Flow, V = 2000 veh/hr
Peak 15-min flow = 600 veh
Peak-hour factor = 2000/ (4*600) = 0.83
Trucks and Buses = 12 %
RVs = 6 %
Rolling Terrain
fHV = 1/ (1 + 0.12 (2.5-1) + 0.06 (2.0-1)) = 1/1.24 = 0.806
fP = 1.0
Peak Flow Rate, Vp = V / (PHV*n*fHV*fP) = 2000/ (0.83*3*0.806*1.0) = 996.54 ~ 997 veh/hr/ln
Vp < (3400 – 30 FFS)
S = FFS
S = 54.6 mph
Density = Vp/S = (997) / (54.6) = 18.26 veh/mi/ln
