The Washington State Department of Transportation has finally done it: They’ve made it nearly impossible for the average person to calculate the price of a ferry ticket.

First, prices for everyone go up 2.5 percent in October. But don’t get used to it, the price goes up again, by 3 percent next May 12. The ferry system in a news release depicts this as good news, because it precludes the need for another increase in October 2012. Of course, that good new may not last considering the Legislature meets between now and then.

In addition, everyone will be hit by a 25-cent bonus charge, with the money earmarked for “vessel replacement.” It might take a while for all those quarters to add up to enough to buy a new $100 million ferry. Perhaps “vessel replacement” means a flat barge pulled by a tugboat.

To complicate matters further, the ferry system reserves the right to add a fuel surcharge once diesel fuel, based on the present price, reaches  $4.08 a gallon. What are the chances of that happening with the “Arab Spring” under way? No greater than 100 percent, certainly.

But perhaps the most confusing aspect of the entire rate overhaul is the new “car size based categories,” in which a standard car length is defined as 14 to 22 feet, up from the present 20 feet. The good news, according to State Ferries, is that cars shorter than 14 feet will actually pay less, which will entice people to use shorter cars, which in turn will allow more cars on each ferry. Eventually, short cars will cost 30 percent less.

Hardly anyone knows how long his or her car is. Islanders will be measuring like crazy to get the cheaper fee. If a so-called “Island Beater” is  14-feet, 6-inches, rolling it into a tree should make it just short enough to get the cheaper ferry ticket. Ferry officials will have to change the policy to include “not counting dents,” or most island cars will look like they just had nose jobs.

We can see it now. A family of mainlanders including mom, dad, grandma, grandpa and three kids decides to take their $2,500, 15-foot ‘92 Grand Caravan to the island for a day of fun and shopping. But then they notice their rig is charged 30 percent more than 2012 Mercedes Benz SLK costing $54,800, measuring only 13.4 feet, carrying a single man and his dog.

A lot of people in longer cars will be turning around in the parking lot.