Roadway Analysis Flashcards

What term describes the algebraic difference in grade between two intersecting roadway tangents in a vertical curve?

Answer: A-value

The A-value is the algebraic difference in grades (in percent) at the endpoints of a vertical curve and governs curve length design.

When measuring skid marks to calculate pre-impact speed, which segment length is most critical for an accurate minimum-speed estimate?

Answer: The total visible stain length including shadow skids

Including shadow skids and any visible tire marks gives the longest defensible distance, yielding the most accurate minimum pre-impact speed.

A roadway has a 4% upgrade followed immediately by a 2% downgrade. What is the A-value at this crest?

Answer: 6

A = |G1 − G2| = |4 − (−2)| = 6%; the algebraic difference accounts for sign change at a crest.

Which roadway surface condition produces the highest coefficient of friction for a standard passenger tire?

Answer: Dry concrete

Dry concrete typically yields the highest friction coefficients, often 0.70–0.80 for standard passenger tires.

In the context of roadway cross-section, what does 'normal crown' refer to?

Answer: The standard two-sided transverse slope directing water to both edges

Normal crown is the standard pavement cross-section with slopes from the centerline toward both edges to facilitate drainage on tangent sections.

Which type of pavement marking is used to delineate the right edge of a roadway?

Answer: White solid line

White solid edge lines mark the right edge of the traveled way per MUTCD guidelines.

What is the primary purpose of a transition (spiral) curve between a tangent and a circular curve?

Answer: To allow gradual introduction of centripetal acceleration and superelevation runoff

Spiral transitions allow drivers to gradually steer into the curve while superelevation and widening are introduced, improving safety and comfort.