Several Southern Maryland highways will be improved this summer in projects funded through the State Highway Administration.

Construction work is underway on Route 235 in St. Mary's County, Route 765 in Calvert County and U.S. Route 301 in Charles County. In addition, the western end of Route 228 will be widened from two lanes to four. The road is an important commuter route, linking Waldorf with Indian Head Highway.

The St. Mary's project is the biggest in the tri-county area, costing $11 million. Under the first phase of construction, state highway officials said, workers will reconstruct, resurface and widen two miles of Route 235 between Route 4 (St. Andrews Church Road) and Route 246 (Great Mills Road).

Route 235, currently a four-lane divided highway, will be expanded to six lanes, with one additional through lane in each direction. New sidewalks, pedestrian ramps, and curbs and gutters will be added to both sides of the highway, and there will be improvements in storm water management and landscaping.

The work on Route 235 is part of a three-phase effort to ease bottlenecks on the busy highway. The first phase of construction began in April and will be finished by fall 2000. The second phase, set to begin late this year, will include work between Route 237 and Pegg Road.

"This highway is the primary route through the St. Mary's County peninsula to such points as historic St. Mary's City, Point Lookout State Park and the U.S. Naval Air Station on the Patuxent River," Gov. Parris N. Glendening (D) said in a statement. "To ease congestion and improve motorist safety, I was pleased to fund this project."

In Calvert, Route 765 (H.G. Trueman Drive) is undergoing construction that will connect it from Patuxent Point Parkway to the Solomons Landing Condominiums. Sidewalks also will be added. The $2.3 million project will be done by late fall.

In Charles, state highway officials are spending $670,000 to resurface and improve a one-mile southbound stretch of Route 301 between Billingsley Road and Smallwood Drive. The construction began in April and is scheduled to be completed by mid-summer.

And just over the county line in Prince George's, the commuter-heavy Route 228 will be widened between Bealle Hill Road and Route 210 at a total cost of $3.2 million. The project is scheduled to run through late spring 2000.

CAPTION: Ivan Mora, above, excavates a wooded area in Charles County for the expansion of two-lane Route 228 to four lanes. Carlos Salazar, right, saws trees in the same area being excavated by the Driggs construction company.