Brain Reaction Time and Traffic Accidents

Maryland

When you are driving and encounter an unexpected circumstance that could lead to a car accident, quick and decisive action is required to avoid the accident. Perhaps the most important part of your reaction is your brain’s reaction time to the circumstance. You depend on other drivers around you to react just as quickly to avoid hitting you as you complete an accident-avoidance maneuver, like braking or swerving. In trying to understand how liability might be assigned in the accident’s aftermath, we will look closely at the role of brain reaction time in a car accident.

What Is Brain Reaction Time?

It is common  to lump brain reaction time into a single step, as if it were a simple unified item from when you see a circumstance to when you act. But reaction time is actually complicated, composed of several distinct parts. There are several representations of this complex process. The breakdown we give here is from the 2000 article “How Long Does It Take to Stop?” in Transportation Human Factors by Marc Green.

Mental Processing Time is the time it takes to perceive a circumstance and decide on a response, what most people refer to as reaction time. This time can be broken into several components:

• Sensation–this is the time it takes to tell there is something in or around the road
• Perception/recognition–this is the time it takes to recognize the identity of the sensation or stimulus, such as brake lights or a child pedestrian in the road.
• Situational awareness–this is putting the stimulus in the context of driving, such as deciding “will I hit this person/object if I don’t respond?”
• Response selection–this is deciding which of the many possible responses will yield the best results

Movement Time is the time it takes for your body to follow the brain’s instructions

Mechanical Response Time is the time it takes for your car to respond to the movement of the controls such as turning the wheel or pressing the brake pedal

How Long Is Brain Reaction Time?

The two most constant parts of the reaction time are mechanical response time and movement time. Mental processing time, on the other hand, is highly variable. Traditionally, mental processing time–what is sometimes called reaction time–for a normal driver under good conditions was assumed to be about 0.75 seconds. However, more detailed studies have shown that reaction times are often longer than a full second for an alert driver, and, depending on different factors it may be two seconds or more. This is because the mental processing time is actually composed of many separate tasks, each of which may be impacted by diverse factors.

• Sensation is affected by a person’s visual acuity
• Perception/recognition is affected by the location of the eyes, since it is much harder to recognize objects outside our central vision area
• Situational awareness can be affected by multitasking and whether the stimulus is expected or unusual, which is directly related to a person’s driving experience
• Response selection can be lengthened by a lack of experience, and, like all the other elements, by intoxication and alertness level

Studies have shown that reaction time can be dramatically lengthened by intoxication or distraction, making drivers far more likely to be involved in accidents. Studies have shown that cell phone use is at least as dangerous as drunk driving in terms of slowing reaction time and increasing the likelihood of an accident.

Stopping Distances

Let’s consider the best-case scenario for a car traveling at highway speeds. During the traditionally-assumed 0.75 seconds of processing time, a car traveling at 65 mph will travel over 70 feet. Movement time to apply the brake then takes about 0.3 seconds, during which time the car will travel another 28 feet. Actually stopping the car with good tires on dry pavement requires at least 188 feet. Under the best conditions, therefore, an alert driver can avoid hitting any obstacle perceived at a distance of 300 feet or more. When the brain reaction time lengthens to one and a half seconds, such as it might when a person is looking at a different part of the road, the stopping distance increases to over 350 feet. When reaction time lengthens to two seconds, an estimate of the effect of basic distractions such as changing the radio station or talking on even a hands-free cell phone, the stopping distance increases to over 400 feet. This means that even minor distractions can cause an accident even if the driver is following at a responsible 2-second distance (about 200 feet at 65 mph).

The problem of distraction becomes even worse if the following vehicle is a large truck, which may require over 250 feet for the brakes to stop the truck, increasing the best possible stopping distance to 350 feet at 65mph. A distracted truck driver will require nearly 500 feet on a dry road, with good tires, and a truck that is not overloaded. Distraction or any other factor that slows a truck driver’s reaction time becomes a critical event in truck accidents. In fact, a recent study of commercial vehicle accidents by the Federal Motor Carrier Safety Administration (FMCSA) showed that truck drivers were engaged in distracting, non-driving tasks in 71 percent of crashes.

If you were in an accident caused by a distracted or inattentive driver, the car accident lawyers at Chaikin, Sherman, Cammarata, & Siegel, P.C. can help. Please call or email us today to learn more.