After watching a two-week shutdown of the Federal Aviation Administration, transportation advocates and congressional staffers are concerned that the federal gas tax could become the next confrontational issue that Democrats and Republicans push to the brink. The Senate and House are in the process of considering a long-term highway bill. Passing a short-term extension while they work out the details of a longer measure would normally be considered routine, but so was a short-term extension of FAA funding. That all changed July 23, when 4,000 FAA workers were furloughed for nearly two weeks as the House and Senate could not...