Perception reaction time

Driver Information Processing Attention, Perception, Reaction Time and Comprehension... 

A significant percent of all crashes are attributed to delayed recognition of the imminent danger (see Chapter 17). This means that either the critical event or object was not recognized at all before the crash or the perception reaction time was delayed to such an extent that by the time the driver responded to the situation it was too late. In this chapter we discuss the impact of the attention process and decision process on the perception reaction time. We then focus on some specific situations that require very specific information processing capabilities such as maintaining a safe headway and passing other vehicles. Finally we discuss the issue of comprehension of various symbols to which we have to attend - in and out of the vehicle. 

Perception Reaction Time And Brake Reaction Time... 

It should be clear by now that it takes time to see and respond . The expression to stop on a dime is just that an expression. The time it takes from the moment a sound wave reaches our eardrum, or a light ray impinges on our retina, until we initiate a response to that stimulus is known as perception reaction time. In driving, the time that passes from the moment a stimulus - such as a brake light or a stop light - appears until we actually reach the brake pedal is known as brake reaction time (BRT). 

In driving perception reaction time is a critical component in any emergency maneuver, such as the ones that often precede a crash. This becomes evident if we consider the distance that a vehicle requires to come to a complete stop from the moment that an imminent danger appears. The total stopping distance (TSD) - from the moment a stimulus impinges on our sensory system until the car comes to a full stop can be calculated from the following equation (AASHTO, 1994) ... 

As we move away from the sterile laboratory environment to a more complex one such as a driving simulator, or an experimental study on the road, or a naturalistic road study we can expect perception reaction times and brake reaction times to increase. And they do. In a review of 31 studies of brake reaction time. Green (2000) noted that mean times varied from a short 0.42 seconds (when drivers in a simulator responded to an expected light while impaired by carbon monoxide Wright and Shephard, 1978) to a high of 1.95 seconds (for older drivers responding to an unexpected stop by a policeman Summala and Koivisto, 1990). 

Figure 5-2. Perception reaction times (PRTs) and foot movement times (MTs) to a brake light, in a laboratory situation. PRTs are from the onset of the brake light to the initial release of the accelerator pedal. MTs are from the accelerator pedal to the brake pedal. Total braking reaction time is the sum of PRT and MT (from Warshawsky-Livne and Shinar, 2002, with permission from Elsevier).

There was a possibility, in our study, that the shorter headways were maintained by those who had faster reaction times. Therefore, we examined the perception reaction time in optimal laboratory conditions to see how well it related to the headways the drivers kept on the road. 

The results were disappointing. The correlation between the two measures was essentially zero. Not only that, but for 7 of the 30 people who participated in the study the average perception reaction time under optimal conditions was actually longer than the minimum headway they kept on the road. For these drivers, were that car ahead to stop suddenly, the likelihood of colliding with it was very high. However, this lack of correlation between the headways drivers keep and their brake reaction time should be investigated further, since at least one study found a positive correlation between the two, showing that those who keep short headways have quicker reaction times (Van Winsum and Brouwer, 1997). 

Other additional studies or pertinent information which lend support to this MRL Rats exposed to 1,000 ppm trichloroethylene for 3 days showed disturbed sleep cycles (Arito et al. 1993). Rats exposed to 250 ppm for less than 8 hours showed decreased electric shock avoidance and frequency of Skinner box lever press (Kishi et al. 1991). Humans exposed to 27 ppm trichloroethylene for up to 4 hours noted drowsiness, and headache was reported at 81 ppm (Nomiyama and Nomiyama 1977). Humans exposed for 8 hours to 110 ppm showed decreased performance on perception, memory, reaction time, and manual dexterity tests (Salvini et al. 1971). 

Cognitive and subjective effects The effects of LSD on attention have been examined in animal paradigms. LSD reduces accuracy on a multiple-choice reaction time task, which is reversed by a 5-HT2 antagonist (Carli and Samanin 1992). LSD produces gross alterations in time perception, which holds true in animal models as well as human reports (Frederick et al. 1997). 

Hours Eyes bloodshot. Tired and somewhat dizzy on standing. Reaction time prolonged. Mouth dry. Speech and behavior normal. At 4 hours begins to find everything laughable. Appears euphoric. Definite changes in perception. 

Excess consumption of alcohol is not healthful, as many people will testify. Ethanol is a depressant and can be a mild tranquilizer or a general anesthetic, depending on how much is consumed over what period of time. At low doses, ethanol depresses some of the brain s inhibitory systems and acts as a social lubricant. It can also exacerbate seizure disorders such as epilepsy by depressing the inhibitory systems in the brain that suppress seizures and convulsions. At higher doses, alcohol leads to the classical symptoms of intoxication unsteady walk, slurred speech, altered sensory perception, slow reaction times, bizarre behavior, and finally, loss of consciousness. Consnmption of a fiffh of a gallon of hard liqnor over a short time period can be fatal. 

The Delta system contains many of the same tests contained in the APTS system, including those that monitor motor function, reaction time, attention and working memory, learning and memory, spatial perception and reasoning, mathematical calculation, and language (Table 6.1). More complete descriptions of the psychometric and validity studies supporting the utility of this testing system are available elsewhere.61,62... 

Two key findings emerged. First, drinking alcohol and Red Bull together reduced the perception of headache, weakness, dry mouth, and motor coordination impairment. Second, Red Bull did not significantly reduce alcohol-related deficits on the measures of motor coordination and visual reaction time. 

Major impairment in balance and movement. Large increase in reaction time. Large impairment in judgment and perception. 

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