ACTAR Cheat Sheet 2026

The 30 highest-yield ACTAR facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. What is the significance of the 'static stability factor' (SSF) in rollover analysis? → SSF = track width / (2 × CG height); higher SSF means greater rollover resistance
2. Which evidence type helps determine crash severity? → Crush damage measurements
3. When analyzing a roadway cross-section, what is the typical maximum allowable superelevation for a rural highway in the US? → 8%
4. In crash reconstruction, 'paint transfer evidence' is primarily used to: → Match vehicles involved and establish contact points and geometry
5. What role does collaboration play in photogrammetry for ACTAR professionals? → It enhances outcomes through diverse perspectives and shared expertise
6. When a ACTAR professional makes an error in documentation, the CORRECT procedure is to: → Draw a single line through the error, initial, date, and write the correction
7. A vehicle traveling uphill on a grade of 5% has an effective drag factor that is: → Increased by 0.05 compared to level road
8. In ACTAR practice, what is the best approach to quality improvement in human factors? → Use data-driven methods with measurable outcomes
9. The kinetic energy of a 4,000-lb vehicle (mass ≈ 124.3 slugs) traveling at 44 ft/s is approximately: → 120,400 ft-lbs
10. Which document is the primary federal reference for pavement marking colors, patterns, and placement in the United States? → Manual on Uniform Traffic Control Devices (MUTCD)
11. Why is drag factor important? → It influences deceleration rate
12. Which type of skid mark pattern is most indicative of a vehicle in a yaw (sideslip) condition? → Curved marks with striated edges showing sidewise scrubbing
13. The coefficient of restitution (e) for a perfectly plastic (inelastic) collision equals: → 0.0
14. How is kinetic energy calculated? → velocity / time
15. A vehicle leaves a 4-inch curb traveling horizontally and lands 18 feet away. What was the approximate speed at launch? → 38.4 mph
16. A driver claims they 'looked but didn't see' a motorcyclist before a collision. Which human factors explanation best accounts for this? → The motorcycle was in a visual scan but not attended to (looked but not seen)
17. What is the purpose of the 'perception-reaction time' (PRT) in reconstruction speed calculations? → To determine the distance the vehicle traveled before the driver began braking
18. How long should ACTAR professionals typically retain official documentation and records? → According to applicable regulatory requirements and organizational policies
19. When calculating the speed of a vehicle from a critical-speed yaw mark, which measurement is most critical? → Radius of the curved tire mark
20. Which type of damage pattern is most indicative of a vehicle rolling over during a collision? → Distributed damage on the roof, A-pillars, and door sills consistent with ground contact
21. What is the primary purpose of a transition (spiral) curve between a tangent and a circular curve? → To allow gradual introduction of centripetal acceleration and superelevation runoff
22. What is the primary function of a 'rumble strip' placed on a roadway shoulder? → To alert drowsy or inattentive drivers that they are leaving the travel lane
23. Which EDR data parameter is MOST directly useful for determining whether a vehicle's brakes were applied in the 5 seconds before a crash? → Brake switch status recorded in the pre-crash data frame
24. Which type of evidence is MOST susceptible to degradation or loss if the crash scene is not documented promptly? → Skid mark evidence on roadway surfaces
25. Which term describes the ratio of the relative separation speed to the relative approach speed of two colliding objects? → Coefficient of restitution
26. During a weight transfer event (braking), how does the normal force distribution change? → Normal force increases on front axle and decreases on rear axle
27. Which type of lens distortion most significantly affects photogrammetric accuracy and must be accounted for during camera calibration? → Radial (barrel or pincushion) distortion
28. When using the 'time-distance' method to reconstruct speed from a surveillance video, what is the primary source of error? → Lens distortion causing parallax error in distance measurements
29. What is the significance of the 'point of curvature' (PC) in roadway geometry? → The point where a tangent transitions into a horizontal circular curve
30. Which of the following best describes a 'gore area' in roadway design? → The triangular area between a through lane and a diverging exit ramp