FAQ
Frequently asked questions
Answers to questions attorneys often ask about working with a human factors expert witness in a motor vehicle accident case.
What does a human factors expert witness do in a motor vehicle accident case?
A human factors expert witness helps a judge or jury understand the driver's side of a crash: whether, and how soon, a driver could have seen, recognized and responded to a hazard. The analysis asks what information was available to the driver, whether and when it could be noticed and understood, and how long a response would reasonably take. These questions arise in accidents involving pedestrians, motorcycles and commercial vehicles as well as passenger cars.
How is human factors analysis different from accident reconstruction?
Accident reconstruction establishes where the vehicles were and how fast they were moving. Human factors analysis starts from that work and asks what the people involved could perceive and do in the time available. Christine does not reconstruct crashes; she works from the reconstruction and the case record. The page on human factors and accident reconstruction compares the two.
When should an attorney consider a human factors expert witness?
Attorneys retain a human factors expert witness when a case turns on questions about driver attention, visibility or reaction time: for example, whether a driver was distracted by a cell phone, whether a hazard could be seen and recognized at night, or how much time and distance a driver needed to perceive and react. If it is unclear whether a case raises these questions, a case inquiry is the first step.
What kinds of cases raise human factors questions?
Human factors questions arise in motor vehicle accident cases involving pedestrians, motorcycles and commercial vehicles as well as passenger cars. Examples include rear-end collisions with slow or stopped vehicles, left-turn and intersection crashes, and crashes at night or in work zones. The practice focuses on ten areas: distracted driving, perception-reaction time, hazard detection, nighttime visibility, looming and closing speed, gap judgment and acceptance, traffic signs and control devices, driver expectancy, young and novice drivers, and impaired driving and driver performance.
Does the practice work for plaintiffs or defendants?
Both. The practice accepts civil and criminal engagements from plaintiff, defense and prosecution counsel. The role is to analyze, not to advocate, and the analysis is the same whichever side retains the practice.
What is perception-reaction time?
Perception-reaction time is the interval between the moment a hazard becomes visible to a driver and the moment the driver begins to respond, for example by braking or steering. In the research literature it is usually called perception-response time. It is not a single fixed value, and many conditions can lengthen or shorten it. The article on perception-reaction time explains more.
What does “looked but failed to see” mean?
“Looked but failed to see” describes crashes in which a driver appears to have looked toward a hazard yet did not register it. Researchers connect this to inattentional blindness: people can fail to notice an object that is plainly visible when their attention is directed elsewhere or when the object is unexpected. Depending on the facts, these questions can point in either direction, as the article on hazard detection and “looked but failed to see” explains.
What is looming in a rear-end collision case?
Looming is the growth of a vehicle's image in a driver's view as the distance to it closes, and it is the main cue drivers use to judge closing speed. At long range that image grows slowly, so a driver can see a vehicle ahead well before being able to tell that it is stopped or moving slowly. The article on looming and closing speed explains more.
What is gap acceptance in a left-turn accident case?
Gap acceptance is a driver's decision that a gap in traffic is long enough to turn or cross. Driving research has measured the gaps that drivers typically accept and reject, which offers a way to compare one driver's decision with what drivers generally do in similar circumstances. The article on gap judgment and acceptance explains more.
What are driver expectancy and positive guidance?
Expectancy is a driver's readiness to respond to situations in predictable ways, built from experience with roads in general and with the road being driven. Positive guidance is the related principle that a road should give drivers the information they need, where they need it and in a form they can use. The article on driver expectancy and positive guidance explains more.
What does a human factors expert witness add in an impaired driving case?
Toxicology establishes what was in a driver's system. A human factors analysis asks how the driver's performance before the crash compares with what would be expected of a sober, attentive driver, and whether such a driver could have avoided the crash. The article on impaired driving and driver performance explains more.
Where is the practice based, and does it take cases outside Texas?
The practice is based in Bryan, Texas, within about three hours' drive of Houston, Austin, Dallas–Fort Worth and San Antonio. It accepts cases from attorneys throughout Texas and nationwide. Christine travels for inspections and gives deposition and trial testimony in state and federal courts.
What are Christine Yager's qualifications?
Christine has more than a decade of experience as a transportation safety researcher at the Texas A&M Transportation Institute. She holds bachelor's and master's degrees in industrial and systems engineering from Texas A&M University. Her full qualifications are on the expert page.
These answers are general information, not legal advice or an expert opinion on any matter. See the disclaimer.
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