(WASHINGTON) — Yellowstone National Park reopened three of its five entrances to visitors on Wednesday after unprecedented flooding closed the park on June 13 and reshaped many of its rivers, canyons and roads.

The south loop’s Cody, West Yellowstone and Grand Teton/Jackson entrances opened at 8 a.m. on Wednesday. The Madison, Old Faithful, Grant Village, Lake Village, Canyon Village and Norris areas of the park will again become accessible to visitors.

The park’s northern region, including Lamar Valley and Mammoth Hot Springs, will remain closed until at least early July, park officials said.

Many of the park’s famous wildlife-viewing areas will also be unavailable to visitors returning to the south loop region of the park.

Main routes into the Montana tourist towns of Gardiner, Red Lodge and Cooke City continue to be closed off.

A statement from the National Park Service said that park staff have engaged over 1,000 business owners, park partners, commercial operators and residents in the surrounding gateway communities to help create a plan for how to manage summer visitation while the park’s north loop remains closed.

“It is impossible to reopen only one loop in the summer without implementing some type of system to manage visitation,” the park’s superintendent, Cam Sholly, said in a statement.

The park has subsequently instituted an interim visitor access plan, coined the Alternating License Plate System (ALPS), to balance the demand for visitor access, park resource protection and economic interests of the local communities.

Park officials said the plan was suggested by those from gateway communities during a major public engagement with the park last week. They added that the National Park Service will actively monitor the new system while also building a new reservation system that can be implemented if needed.

According to ALPS, visitation will essentially be monitored based on a vehicle’s license plate.

For public vehicle entry, it will not matter if the last numerical digit on the plate is odd or even. For all others, entrance will be granted based on the odd and even numbered days of the calendar month, so that odd-numbered ending license plates will be able to enter on odd days and vice versa for those ending in even numbers.

For vehicles with personalized license plates that only contain letters, entry will be granted along with odd-numbered ending plates. Vehicles with a combination of letters and numbers that end in a letter will be granted entry on even-numbered days.

Park officials have stated that under this new plan, entrance station staff will turn away vehicles that do not follow the odd-even structure.

There are some exceptions. For one, current commercial use operators with active commercial use permits can enter on any day, including those with commercial tours and stock groups. Commercial motor coaches will also be permitted to enter regardless of their license plate makeup.

Visitors who have proof of overnight reservations in the park’s hotels, campgrounds and backcountry reservations may also be permitted entry regardless of the day’s number status. Essential services such as mail, employees and contractors will be able to enter any day as well.

Regardless of license plates, motorcycle groups will only be permitted into the park on even days.

The ALPS plan is temporary, as the park braces for its summer season while managing its partial-capacity status.

Sholly said that as repairs continue across the park, park officials will work to reopen new sections throughout the summer.

“It is critical for visitors to stay informed about this interim system as we evaluate its effectiveness. They should plan ahead and be patient with us as we are still managing significant recovery while moving into this operational phase,” Sholly said.

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