CEE 551 Traffic Engineering

Homework #3

Question 1 (15 points)

Estimate the flow-flow speed of a four-lane undivided multilane highway having the following characteristics:

• Base free-flow speed = 60 mi/h
• Average lane width = 11 ft
• Lateral clearance = 3 ft at both roadsides
• Access point density = 15/mi on each side of the roadway.
• Good weather, no incidents, no work zones, and regular users of the facility may be assumed.  

Question 2 (15 points)

Estimate the free-flow speed of a six-lane suburban freeway with 12 ft lanes, a right-side lateral clearance of 2ft, and ramp density of 3.5 ramps/mi. Normal conditions, i.e., good weather, no incidences, no work zones, and regular users of the facility, may be assumed.

Question 3 (10 points)

What average grade would be used to analyze a segment with 1,000 ft of 2% upgrade followed by 1,500 ft of 3% upgrade?

Question 4 (10 points)

A freeway operating in generally rolling terrain has a traffic composition of 15% trucks (standard mix). If the observed peak hour demand is 3,200 veh/h (in one direction), what is the equivalent volume in passenger car equivalents?

Question 5 (25 points)

Find the upgrade and downgrade service flow rates and service volumes for an eight-lane freeway with the following characteristics:

• 11 ft lanes
• 2 ft right-side lateral clearance
• 4.2 ramps/mile
• 3% trucks (standard mix; standard mix, which means for freeways is 30% SUTs/70%TTs)
• Good weather, no incidents, no work zones, and regular drivers
• PHF = 0.92

The segment in question is on a sustained grade of 3.5%, 1.5 miles in length

Question 6 (25 points)

A six-lane recreational freeway has the following characteristics:

• 12 ft lanes
• 6 ft right-side lateral clearance
• 2 ramps/mile
• 10% trucks (standard mix, which means for freeways is 30% SUTs/70%TTs))
• Good weather, no incidents, no work zones, and regular drivers
• PHF = 0.95
• Level terrain
• Peak hour demand = 4,000 veh/h

Because the facility services recreational users to a nearby ski area, the peak period occurs on weekends, and light to moderate snow is the normal weather pattern. If virtually all uses of the facility are unfamiliar with the roadway, what is the expected LOS during the peak period?