2. Key Differences B/W Freeways and
Multilane Highways
Vehicles access; no full access control for
multilane highways
Multilane highways may or may not be
divided
Traffic signals may be present
Design standards, e.g. speeds are lower as
compared to freeways
More distraction along the multilane highway
5. Base Conditions for Multilane Highways
LOS Analysis
12 ft lane width
12 ft min total lateral clearance from road
side objects (right shoulder and median)
Only passenger cars in traffic stream
No direct access points
Divided highways
Level terrain
Familiar drivers
FFS of 60 mph or more
6. FFS
• FFS = BFFS – fLW - fLC - fM - fA
• BFFS ;
– 7 mph + posted limit of 40 to 45 mph
– 5 mph + posted limit of 50 mph or higher
• fLW = Lane width adjustment factor (Same as
freeways)
• fLC = Lateral clearance adjustment factor
7. fLC Lateral clearance adjustment factor
• TLC = LCR + LCL
• TLC = Total Lateral Clearance
• LCR = Right side lateral clearance to obstruction
• LCL= Left side lateral clearance to obstruction
• For undivided highways: LCL= 6 ft
• If lateral clearance on any side exceeds 6 ft, it is
taken as 6 ft.
28. Density
D = vp / S
• FFS = 52 mph
• Flow Rate = 1500.3 pc/hr/ln
• Average Passenger Car Speed (S) = 52 mph
• Density (D) =
= Flow Rate (pc/h/ln) / Average Passenger Car
Speed = 1500.3/52 = 28.85 pc/mi/ln