ACTAR Roadway Analysis 5 — Questions and Answers
Question 1: What is the primary function of a 'rumble strip' placed on a roadway shoulder?
- To channelize pedestrian crossings
- To alert drowsy or inattentive drivers that they are leaving the travel lane (Correct answer)
- To provide additional braking friction in curves
- To delineate the centerline in fog conditions
Correct answer: To alert drowsy or inattentive drivers that they are leaving the travel lane
Shoulder rumble strips create audible and tactile warnings to alert drivers who drift off the travel lane before a run-off-road crash occurs.
Question 2: In forensic roadway analysis, what is the purpose of measuring 'cross-slope' or 'transverse slope' at a crash location?
- To determine the posted advisory speed for the curve
- To calculate how pavement slope affects vehicle stability and speed calculations (Correct answer)
- To verify that lane widths meet AASHTO minimums
- To document the sight distance available to the driver
Correct answer: To calculate how pavement slope affects vehicle stability and speed calculations
Cross-slope affects the lateral forces on a vehicle and must be accounted for in friction and speed calculations, especially on curves or icy roads.
Question 3: Which document is the primary federal reference for pavement marking colors, patterns, and placement in the United States?
- AASHTO Green Book
- Manual on Uniform Traffic Control Devices (MUTCD) (Correct answer)
- Highway Safety Manual (HSM)
- HCM (Highway Capacity Manual)
Correct answer: Manual on Uniform Traffic Control Devices (MUTCD)
The MUTCD, published by FHWA, is the national standard governing all traffic control devices including pavement markings on public roads.
Question 4: A roadway is described as having a '3% grade.' What does this mean?
- The road rises 3 feet for every 100 feet of horizontal distance (Correct answer)
- The road drops 3 inches per mile
- The superelevation is set at 3% on the curve
- The road has a 3-degree horizontal deflection angle
Correct answer: The road rises 3 feet for every 100 feet of horizontal distance
A 3% grade means the elevation changes 3 feet vertically for every 100 feet of horizontal (plan) distance.
Question 5: When reconstructing a crash at an intersection, what is the most important role of the 'functional area' concept?
- It defines the area where pedestrians have the right-of-way
- It identifies the zone where drivers are responding to the intersection and where conflicts are most likely (Correct answer)
- It specifies the minimum turning radius for trucks
- It delineates the area requiring full-depth pavement repair
Correct answer: It identifies the zone where drivers are responding to the intersection and where conflicts are most likely
The functional area of an intersection is the upstream zone where drivers perceive, decide, and react to traffic control, making it critical for analyzing perception-reaction conflicts.
Question 6: Which field measurement technique is used to determine the grade of a roadway segment using a digital level and rod?
- Differential leveling (Correct answer)
- Triangulation survey
- Total station traverse
- GPS waypoint averaging
Correct answer: Differential leveling
Differential leveling measures elevation differences between points using a level instrument and graduated rod, yielding accurate grade calculations for crash scene surveys.
Question 7: In roadway departure crash analysis, what does 'clear zone' refer to?
- The visibility corridor required for a sight-distance analysis
- The unobstructed roadside area beyond the traveled way where an errant vehicle can safely recover or stop (Correct answer)
- The painted buffer zone between opposing travel lanes
- The minimum gap required for left-turn movements
Correct answer: The unobstructed roadside area beyond the traveled way where an errant vehicle can safely recover or stop
The clear zone is the roadside recovery area free of fixed hazards that gives errant vehicles space to stop or return to the roadway safely.
ACTAR Roadway Analysis 5
What is the primary function of a 'rumble strip' placed on a roadway shoulder?