Roadway Design & Engineering Flashcards

What is the purpose of a 'passing sight distance' standard on two-lane roads?

Answer: To define the distance required to safely pass a slower vehicle before oncoming traffic arrives

Passing sight distance is the minimum sight distance required to allow a driver to safely complete a passing maneuver before encountering oncoming traffic.

Which road element is designed to slow vehicles by increasing discomfort at high speeds?

Answer: Rumble strips

Rumble strips create vibration and noise when driven over, alerting drivers that they are traveling too fast or drifting out of lane.

What does 'ADT' stand for in traffic engineering?

Answer: Average Daily Traffic

ADT (Average Daily Traffic) is the total traffic volume on a road segment during a given time period divided by the number of days in that period.

In pavement design, what is the purpose of a 'base course'?

Answer: To distribute loads from the surface to the subgrade

The base course distributes traffic loads over a wider area before they reach the subgrade, preventing premature pavement failure.

What is a 'diverging diamond interchange' (DDI) primarily designed to improve?

Answer: Left-turn movements to and from freeway ramps without signal phases

A DDI temporarily crosses traffic to the opposite side, eliminating left-turn conflicts and reducing the number of signal phases needed for freeway ramp movements.

What does a higher 'K-value' indicate in vertical curve design?

Answer: A longer, more gradual vertical curve for a given algebraic grade difference

The K-value represents the length of vertical curve per percent of algebraic grade difference; a higher K-value means a flatter, longer curve.

Which type of interchange is most commonly used on US Interstate highways?

Answer: Diamond interchange

The diamond interchange is the most common interchange type on Interstate highways due to its simplicity, compact footprint, and cost-effectiveness.