Acadia National Park is reminding visitors that they are supposed to pay a fee to be in the park by posting signs that say “fee area.” The problem with this nice, but vague, approach is that people who don’t realize national parks charge entrance fees aren’t likely to be persuaded by small road signs.

As a first step toward ensuring more people pay the park’s entrance fee, Acadia earlier this year installed small signs at 33 entry points to the park. Below large signs saying “Entering Acadia National Park” smaller ones that read “U.S. Fee Area” have been installed. Without directing them to a place to pay or saying how much the fee is, the signs are likely to have only a small impact.

There are several difficulties for Acadia. With dozens of access points to the sprawling park, which is criss-crossed by numerous public roads on Mount Desert Island, it is impossible to set up entrance stations at each of these points. Putting up signs that detail all the fee options and directing people to places where they can pay would be cumbersome. Allowing people to deposit their fees in unattended boxes in the woods could invite vandalism and compliance likely wouldn’t be great either, said the park’s fee manager, Ranger Kevin Langley.

That’s why the park settled on the new signs as a first step with the goal of raising awareness.

Park officials estimate about 60 percent of those who visit the park by vehicle pay the entrance fee. Most who do not say they didn’t realize there was a fee to be in the park. A smaller portion object to paying. Getting the latter to pay will be difficult, but the uninformed can be changed.

Acadia spreads the fee message through its publications and on its Web site. Riders of the Island Explorer bus are reminded to pay and those who stay in a campground are required to.

For most summer visitors, weekly passes cost $5 for individuals and $20 per vehicle. Annual vehicle passes cost $40. They may be purchased at the park’s only fee station, on the Park Loop Road near Sand Beach, at the park’s visitor center, and at the information center on the Village Green in Bar Harbor.

The park is looking at the possibility of selling passes through other vendors, which would help. Making passes easily available online would also be a big improvement. Passes to all federal lands may be purchased online through the U.S. Geological Survey, not the place park visitors are likely to look. Making passes available through individual national park Web sites would be better.

The loss of fee revenue is important because 80 percent of the money stays with the local park, paying mostly for maintenance. With millions of dollars of deferred maintenance at Acadia alone, this missing money would be helpful.

The nice approach may help, but tougher, more informational reminders with easier ways for people to pay are likely to be necessary.