Maryland highway officials announced a double-barreled publicity campaign yesterday aimed at making the five-year, $175 million expansion of I-270 less of a burden on motorists -- and vice versa.

A 24-hour American Automobile Association hot line, a low-frequency AM radio message, informational signs and roving "trouble trucks" are among the strategies for helping commuters deal with delays and lane closings.

At the same time, in an attempt to facilitate construction and to wean some drivers away from the overburdened highway, officials are vigorously promoting mass transit and are lobbying area employers to expand van pooling and ride sharing.

"One problem is that most commuters don't have an alternative to using 270," said Mary Anne Reynolds of AAA's Potomac division. "Route 355 is already at capacity.

"There are 5,700 cars at morning peak on Clopper Road south of Quince Orchard," Reynolds continued. "The council of governments estimates that 80 percent of those are single-occupant cars. If we can get one in five of those drivers to ride-share over the next five years, that would take a thousand cars off the road, and that spells relief."

Said Robert McGarry, chief of the Montgomery County Department of Transportation: "My pitch is that there is an alternative, and that's public transportation."

McGarry said DOT staffers have designed for upcounty commuters a series of routes that lead to the Shady Grove Metro station and bypass I-270. McGarry also said that the Ride-On fleet has been increased from 150 buses to 200, and that DOT is actively notifying employers to promote pooling.

The radio message outlining general construction schedules, to be beamed over the 530 AM frequency from a transmitter at the Shady Grove interchange, will be transmitted up to five miles. It will not include information about traffic or accidents. State Highway Administrator Hal Kassoff said his office has contacted the airborne traffic reporters covering the area to help coordinate emergency information.

The AAA hot line (AAA-6270), which begins operation Monday, also won't track changing traffic conditions, but it will give motorists a schedule of construction activity for the next 24 hours.

Over the next five years, the entire length of I-270 from the Y-split just north of the Capital Beltway to the Rte. 121 interchange north of Germantown will be expanded from six to eight lanes. In addition, two-lane "collector-distributor" roads will be constructed on each side, allowing for smoother access and also serving local traffic.

The existing interchanges will be improved, and four additional interchanges will be constructed at Falls Road, Middlebrook Road, Clopper Road and I-370, a three-mile highway that will take upcounty commuters from I-270 directly to the Shady Grove subway.

State Highway Administration district engineer Michael Snyder said contruction of I-370 and work on the Rte. 117 interchange is scheduled to begin this fall, followed by construction of a second overpass at Shady Grove Road.

Snyder said that construction will force single-lane closings at off-peak hours, and that between 11 p.m. and 5 a.m., two lanes may be closed occasionally.

At some period, all three lanes will need to be closed for 15-minute intervals between 11 p.m. and 5 a.m. while steel girders for the second Shady Grove overpass are being erected.

However, Kassoff said the highway agency is committed to maintaining the current number of lanes and will resurface some median or shoulder areas as necessary to divert traffic.

Ninety percent of the cost of the project is being borne by the federal government, with the state paying for 9 percent of the cost and the remainder of funds being provided by the county.