The Northern New England Passenger Rail Authority, which oversees Amtrak Downeaster service between Maine and Boston, has gotten a lot of government attention over the past year. Even the LePage administration, usually an opponent of red tape, has been a major player, taking oversight of and stalling the approval process for a proposed Amtrak layover facility, whose stormwater permit will be the subject of a state hearing next week.

Now legislators have green-lighted an audit of the rail authority by the Office of Program Evaluation and Government Accountability. Because the probe was requested by another outspoken rail authority critic, Sen. Stan Gerzofsky, D-Brunswick, the credibility of the inquiry hinges on the involvement of the state watchdog. The layover facility is not the focus of the audit; the probe may be a worthwhile housekeeping measure, as long as it doesn’t turn into a politically motivated witch hunt.

The Amtrak Downeaster has been operating in Maine for about 13 years, and it’s been a bumpy trip of late. The Downeaster operates 10 trains daily between Portland and Boston and four trains per day between Brunswick and Boston. From July 1, 2013, to June 30, 2014, passengers made a record 537,000 one-way trips on the Downeaster, or an average of about 1,400 trips per day.

Ridership increased by 4.6 percent between fiscal 2013 and fiscal 2014, although the service posted its worst-ever on-time performance during the same time period. While 82 percent of trains arrived on time in fiscal 2013, just 58 percent were on time the following year — a number that’s considered substandard under federal law. (A train is “on time” if it reaches its final destination within 10 minutes of its scheduled arrival.) What’s more, 16 trains canceled service in January, and 36 trains canceled last month.

The agency that runs the Downeaster gets $2 million per year from the state of Maine, so it’s due for state review — especially given the service’s recent subpar performance. As the head of the rail authority told legislators last week, such inquiries are “par for the course” for public agencies. Indeed, the Northern New England Passenger Rail Authority, which receives $8 million annually in federal funds, is the subject of periodic federal audits (as well as a yearly internal financial audit).

And the Office of Program Evaluation and Government Accountability is undoubtedly the right body to conduct the state audit of the rail authority. OPEGA, which has evaluated the operations of agencies such as the Maine Turnpike Authority and investigated a Maine Center for Disease Control document-shredding controversy, has a record of introducing hard facts to policy debates.

Gerzofsky called for the audit, and, as a member of the Legislature’s Government Oversight Committee, voted for it as well. The committee’s decision to direct OPEGA to lead the probe should be seen as a signal to Gerzofsky and other critics of the rail authority to step back and let the nonpartisan state watchdog agency do its work without interference. Transparency in government is too important to enable the appearance of a conflict of interest to derail efforts at public accountability.