Some up, some down, the speed limits they are a-changing.

The police department has announced speed limit changes on nine roads or sections of roads in Ridgefield that previously had posted limits of 25 miles per hour — with speeds bumping up on long, straight George Washington Highway, and the most dramatic fall, from 25 to 15, on winding, hilly narrow Pelham Lane.

Most changes were adjustments of five miles per hour and were driven, police say, by local road and traffic factors.

The changes reducing allowed speeds on five roads are:

Lafayette Avenue, from Washington Street to Copps Hill Road, the speed limit drops from 25 to 20 miles per hour.

Pelham Lane, from the Wilton town line to Nod Hill Road, the speed limit falls from 25 to 15 miles per hour.

Rochambeau Avenue, from Copps Hill Road to Washington Street, the speed limit goes down from 25 to 20 miles per hour.

Washington Street, from Rochambeau Avenue to Lafayette Avenue, the speed limit falls from 25 to 20 miles per hour.

Old Sib Road, from the New York line to Rock Road, the speed limit goes from 25 to 20 miles per hour.

The changes increasing allowed speeds on four roads are:

George Washington Highway, the entire length, the speed limit has increased from 25 to 30 miles per hour.

Farmingville Road, from Route 35 to Limekilm Road, the speed limit increases from 25 to 30 miles per hour.

North Street, from Route 116 to Wooster Street, the speed limit goes up from 25 to 30.

Regan Road, for the entire length, the speed limit rises from 25 to 30 miles per hour.

Capt. Shawn Platt, public information officer of the Ridgefield Police Department, said the speed limit changes were all approved by the state.

“Although the Ridgefield Police Commission is the Local Traffic Authority (LTA) for town roads, all speed limits on public roads, whether owned by the state or town, must be approved by the Office of the State Traffic Administration (OSTA),” Platt said.

“The OSTA sets the speed limits on state and local roads based on an engineering investigation.”

Platt added that the factors considered in setting speed limits are:

• road type and surface (curve, hill, etc.);

• location and type of access points (intersections, entrances, etc.);

• existing traffic control devices (signs, signals, etc.);

• accident history;

• traffic volume;

• sight distances;

• test drive results;

• radar observations.

The changes took effect at the end of May.