It should have been easy. Count the number of passengers who ride the Capitol Corridor trains between Roseville, Sacramento, Oakland and San Jose.

But auditors from the state department of finance did just about everything wrong. First, they chose the Labor Day weekend when ridership is always low, to do their count. Worse, they chose last Labor Day, the weekend the Bay Bridge was closed for repairs, a fact that had been widely publicized for weeks.

Cars could not cross the bridge to enter San Francisco and neither could Capitol Corridor buses that take train passengers from Emeryville into the city. People had been warned not to come to San Francisco. Low ridership was guaranteed.

Still, nine of the 22 trips surveyed took place on that weekend. Auditors used those counts to conclude the trains are underutilized.

That flawed conclusion from a flawed survey could be disastrous. State officials are using it to decide when to order coaches which are urgently needed. With coaches, it can take three years from order to delivery. Those coaches need to be ordered now, or passengers will soon find themselves standing all the way to San Jose. If that happens, riders who can’t find seats will know who to blame – the governor’s auditors.

Ginger Rutland writes for The Sacramento Bee opinion pages.