While it may be true that increasing lane widths, resurfacing rough highways, and improving visibility at dangerous intersections may help decrease the number of accidents in Prunty County, the evidence given is not enough for the County to undertake this project. All these measures would increase the quality of the roads, however, without reliable data backing the argument, the County should further analyze the issue.
The author of the argument starts by citing that the reduction of the speed limit didn't decrease the number of accidents. This alone is not enough to justify the investment. The fact that the number of accidents didn't decrease with the new speed limit, can only be used against the new speed limit, and not for the project. It can even be the case that the problem in the highway was due to a case of a low-speed limit. If this happens, it's reasonable to advise an increase in the speed limit, instead of undertaking the project.
Building on that, the author also uses the large number of drivers exceeding the speed limit as support for his argument. This is also not reasonable evidence to support the investment. Given that there was a reduction in the speed limit, maybe this large number of careless drivers is again a result of a low-speed limit. It could happen that these drivers didn't decrease their average speed when the speed limit decreased, so they are still driving at the same speed they were driving before. Both of these pieces of evidence only show us that the change in the speed limit was ineffective.
Lastly, the author gives the example of another County that undertook the same project and had a decrease of 25% of the total accidents through a five-year span. This, supported with more evidence, could be a good way of arguing for the investment, but again we lack data. We know that this decrease is true, but we don't know if it was caused by the new measures implemented by Butler County. Maybe there was a decrease in the number of drivers that could explain it. Maybe the County invested in an advertisement for careful driving, which alone was more effective that the project on the highway. Maybe the citizens of this County adopted safer vehicles. Without these pieces of information, we are unable to reach any conclusion. Only if we find that the only significant change in this County was the changes in the highway, we can have solid evidence that will strengthen the argument.
Theoretically, this project makes sense. Better highway conditions usually decrease the number of accidents. However, with the evidence given we don't know if this is the case. For the first two pieces of evidence used by the author of the argument, he makes the mistake of believing that if the speed limit change was a failure, the alternative of investing in the highway is unconditionally better. It can be the case that it's not. And it can be also the case that there are better alternatives. For the last piece of evidence given, he makes the mistake of assuming that the only significant change in Butler County was the investment in the highway. So, given that all three pieces of information are not capable of influencing us to undertake the project, the County should find better evidence to support it. Otherwise, it should not invest.