What formula calculates minimum radius for horizontal curves using design speed?

R = V²/15(e + f), where R is radius, V is speed, e is superelevation, f is friction

A horizontal curve has radius 800 ft, design speed 45 mph, friction 0.14. Required superelevation rate?

E = (45)²/15(800) - 0.14 = 0.169 - 0.14 = 0.029 or 2.9%

True or False: Superelevation runoff length depends on lane width and relative gradient.

True. Lr = w·ed/0.01·Δ where w is lane width and Δ is relative gradient.

Fill in the blank: For arc definition, degree of curve D = _____ / R.

5729.58

What does the K-value represent in vertical curve design?

Horizontal distance required to effect a 1% change in grade (K = L/A)

Which criterion typically controls sag vertical curve design?
A) Stopping sight distance
B) Headlight sight distance
C) Passing sight distance
D) Comfort

B) Headlight sight distance

Calculate stopping sight distance for 50 mph, 2.5s reaction time, friction 0.32.

SSD = 1.47(50)(2.5) + (50)²/30(0.32) = 183.75 + 260.4 = 444 ft

True or False: Traffic flow rate equals speed multiplied by density (q = u × k).

True. This is the fundamental traffic flow relationship among the three parameters.

What does PHF stand for in traffic capacity analysis?

Peak Hour Factor - ratio of hourly volume to peak 15-minute flow rate

Fill in the blank: Level of Service F occurs when density exceeds _____ pc/mi/ln on freeways.

45

Heavy vehicle adjustment factor fHV = 1/[1 + PT(ET-1) + PR(ER-1)]. What does PT represent?

Proportion of trucks and buses in the traffic stream

Which LOS represents free-flow conditions on basic freeway segments?
A) LOS A
B) LOS B
C) LOS C
D) LOS D

A) LOS A

In AASHTO flexible pavement design, what does the structural number SN represent?

Overall structural strength of pavement layers converted to equivalent thickness units

Calculate SN: 4-inch HMA (a₁=0.42), 6-inch base (a₂=0.14, m₂=1.0), 8-inch subbase (a₃=0.11, m₃=1.0).

SN = 0.42(4) + 0.14(6)(1.0) + 0.11(8)(1.0) = 1.68 + 0.84 + 0.88 = 3.40

True or False: ESALs convert mixed traffic loads to equivalent 18-kip single axle loads.

True. ESAL = Σ(nᵢ × LEFᵢ) where LEF is load equivalency factor.

What is the typical range for clear zone width on highways?

10 to 30 feet, depending on design speed, traffic volume, and roadside slope

Fill in the blank: Resilient modulus MR in pavement design has units of _____.

Psi (pounds per square inch)

Which barrier type provides the least deflection?
A) Cable barriers
B) W-beam guardrail
C) Concrete barriers
D) Box beam

C) Concrete barriers

Why does AASHTO specify maximum superelevation rates for different climates?

Ice and snow conditions require lower rates to prevent vehicle sliding when stopped

True or False: Passing sight distance is typically 3 to 5 times stopping sight distance.

True. PSD requires much greater distances for safe passing maneuvers on two-lane highways.

What happens to required curve radius when design speed increases but superelevation stays constant?

Radius must increase because R = V²/15(e + f) - higher V² requires larger R

Fill in the blank: Standard eye height for stopping sight distance calculations is _____ feet.

3.5

A crest curve has A = 4%, S = 400 ft. Using simplified AASHTO formula, minimum length?

L = AS²/2158 = 4(400)²/2158 = 4(160,000)/2158 = 297 ft

Which factor does NOT affect highway capacity analysis?
A) Heavy vehicle percentage
B) Peak hour factor
C) Pavement type
D) Driver population

C) Pavement type