83. This editorial asserts that West Cambria should not change its highway speed
limits because such changes adversely1 affect driver alertness and are therefore
dangerous. To support this claim, the editorial cites statistics indicating that whenever
East Cambria changed its speed limits, an average of 3 percent more automobile3
accidents occurred during the week after the change than during the week preceding it,
even when the speed limit was lowered. As it stands, this argument suffers from three
critical flaws.
First, it is unlikely that the brief one-week periods under comparison are
representative of longer time periods. A difference of only 3 percent during one
particular week can easily be accounted for by other factors, such as heavy holiday
traffic or bad weather, or by problems with reporting or sampling. Had the editorial
indicated that several speed-limit changes in East Cambria contributed to the statistic2,
the argument would be more convincing; but for all we know, the statistic is based on
only one such change. In any event, a one-week period is too brief to be representative
because it is likely that accidents will occur more frequently immediately following the
change, while people adjust to the new limit, than over the longer term when drivers
have become accustomed to the change.
Secondly4, the editorial fails to acknowledge possible differences in the types of
accidents occurring before and after the change. It is possible that the accidents during
the week before the change all involved fatalities5, while those during the week after the
change were minor6 fender-benders. If so, even though 3 percent more accidents
occurred after the change, the author's argument that changing the speed limit increases
danger for drivers would be seriously weakened.
Thirdly, the editorial fails to take into account possible differences between East
and West Cambria that are relevant to how drivers react to speed-limit changes. Factors
such as the condition of roads, average age and typical driving habits of residents, and
weather patterns, would probably affect how well or how quickly drivers adapt to
speed-limit changes. Thus, changing speed limits in East Cambria might be more
dangerous than changing them in West Cambria.
In conclusion, the statistical7 evidence cited to support the argument is
insignificant8 and probably unrepresentative. To better evaluate the argument, we need to
know how many speed-limit changes contributed to the statistic and when the speed-
limit changes were made. Finally, to strengthen the argument the author should show
that East and West Cambria would be similarly affected by speed-limit changes
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