Major findings related to the frequency of rear-end crashes include the following: (1) work zones for capacity and pavement improvements have the highest frequency compared to other types of work zones; (2) work zones controlled by flaggers are associated with more rear-end crashes compared to those controlled by arrow boards; and (3) work zones with alternating one-way traffic tended to have more rear-end crashes compared to those with lane shifts. Major findings related to the severity of the rear-end crashes include the following: (1) rear-end crashes associated with alcohol, night, pedestrians, and roadway defects are more severe, and those associated with careless backing, stalled vehicles, slippery roadways, and misunderstanding flagging signals are less severe; (2) truck involvement and a large number of vehicles in a crash are both associated with increased severity, and (3) rear-end crashes that happened in work zones for bridge, capacity, and pavement are likely to be more severe than others.
In order to investigate the effect of replacing a human experimenter by a computer in a concept formation task, 150 subjects were run in three conditions. One condition was run exclusively by a human experimenter, another was run exclusively by a computer, and a third was run using the experimenter solely as a teletype operator. The task, designed to be difficult for the college level subject, required that all except one of the 30 possible solutions be logically eliminated before the solution was acknowledged. Subjects run by a human performed a t a slightly higher level than subjects run by computer. This effect, which occurred only in subjects of below average intellectual ability, was attributed to an experimenter cueing effect. Human administered subjects were also found to be significantly less variable regardless of intellectual level. This was partially attributed to a variance dampening effect exerted by human experimenters on their subjects and which is absent from computer administered procedures. One consequence of this effect is that performance in the computerized condition is more highly related to level of intellectual ability. It was concluded that the effects found in this study will probably occur in any computerized procedure characterized by high task difficulty, low time pressure, and wide response latitude.e + .?
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