Which of the following most logically completes the argument?
A recent poll found that over 80 percent of the residents of Nalmed Province favored a massive expansion of the commuter rail system as a means of significantly reducing congestion on the province's highways and were willing to help pay for the expansion through an increase in their taxes. Nevertheless, the poll results contain an indication that expansion of the rail system, if successfully completed, might be unlikely to achieve its goal of reducing congestion, because _______.