Montgomery County officials who exhorted residents to move their cars to the odd-number side of the street by 7 a.m. Tuesday to facilitate snowplowing now say cars can stay on the even-number side as long as the snow emergency is in effect, as the remaining mixture of snow and ice is difficult to shovel.

For the same reason, residents now have 48 hours from the end of the snowfall to clear their sidewalks, instead of 24.

The announcement, during an evening press conference Monday, followed others.

County government will open Tuesday — though many county employees may work from home.

County schools and recreation programs will remain closed.

Chris Conklin, director of the county’s Department of Transportation, said the county had plowed its 1,100 miles of main roads and had completed half the plowing of residential neighborhoods.

A “first pass” on those streets should be done by the end of Tuesday. Conklin said neighborhood streets will be passable, but residents shouldn’t expect to see bare pavement.

Mara Parker, of the county’s Office of Emergency Management and Homeland Security, said snow that’s weighed down by sleet is particularly hard to shovel.

Clearing the remaining blanket feels like shoveling “the equivalent of about 20 inches of snow,” she said. “So please take it slow, take breaks and help your vulnerable neighbors.”

About 75% of the county’s bus services will be operating on Tuesday, Conklin said.