Suburban Maryland bus riders may find commuting into Washington by Metrobus as much as 24 per cent faster in July, when the District opens 11 miles of new priority bus lanes along major commuter routes into the city.

Suburban auto commuters, however, may find their trips will take slightly longer under the D.C. department of transportation plan to improve mass transit here and lessen dependence on commuting by car - the major source of Washington's increasing air pollution.

Almost 5.5 miles of the new but lanes will be placed along both sides of Wisconsin Avenue NW - between Western Avenue and Calvert Street - where buses now must compete with 32,000 cars a day, most of them coming and going during rush hour. With the new bus lanes, the six-lane avenue will have only two instead of the present three lanes of automobile traffic inbound in the morning and outbound at night.

The other major bus lane additions will include almost 2 miles along upper 16th Street NW, about 2.5 miles on Pennsylvania Avenue SE, in Anacostia, and a short eastbound bus lane on M Street in Georgetown to parallel M Street's present westbound bus lane.

In a major study of Washington's existing 27 miles of bus lanes last spring, D.C. transportation officials found that bus travel was actually slower than automobole travel during rush hours along most routes, even those with priority bus lanes.

For instances along M Street in Georgetown in the morning, a major commuter route for many Montgomery County and Virginia commuters, the study found buses were averaging only 8.5 miles an hour, compared with an average 13.6 mph for cars. On Wisconsin Avenue, another major Montgomery County commuter route into the city, local buses averaged only 12 mph during evening rush hours, and express buses to the Maryland suburbs 19 mph, compared to 21 mph for cars.

The study estimates the traveling times of local buses will increase by about 14 per cent and express bus speeds by about 24 per cent with the additional bus lanes and better police enforcement of them.

Illegally parked cars, car commuters driving illegally in the bus lanes and lack of police enforcement were blamed by the study for much of the present delay in bus travel.

Metro's senior bus operations specialist, Ray Russell, said, "Nobody's enforcing the bus lanes anywhere, except occasionally in Virginia, and what enforcement there is extremely erratic." Suburban Maryland has only one short bus lane, a one-mile stretch of Georgia Avenue between the District line and Colesville Road, and presently has no new bus lanes planned.

Russell said in the 15 years since Washington established its first bus lane - on 16th Street NW in 1962 - "I doubt that District police have given more than 15 tickets in that time" to cars driving in bus lanes.

District police officials readily admit that enforcing bus lane regulations has been a low-priority item. The existing bus lanes along Connecticut Avenue, the route for more than 30,000 Montgomery County and upper Northwest Washington car commuters, "are not rigorously enforced because it's something that infuriates the public," at least the car-commuting public, said a Second Police District sergeant whose officers patrol upper Connecticut Avenue. "We don't regularly assign officers over there."

However, city bus lane enforcement can vary from police district to police district, and officers who patrol around South Capitol Street Bridge, where a short bus lane now exists, "have made a special effort to keep the bus lanes open. . . . We sometimes send officers there three days a week and issue as many as 40-50 tickets," said Seventh District watch commander Capt. William R. Anstos.

Earlier this month, Mayor Walter E. Washington proposed an aggressive parking and traffic enforcement campaign in the city, which would more than double the number of parking tickets now being issued. The District also would purchase 25 additional tow trucks to haul off illegal parked cars and recruits a civilian traffic squad of 75 to relieve police of much of the routine parking ticket business.

"We may hear some screams about some of the new priority bus lanes," especially those in Georgetown and along Wisconsin Avenue, says Anthony Rachal chief of mass transit for the city's transportation department. The new bus lanes are being reviewed by Mayor Washington and must receive the blessing of the Environmental Protection Agency, to insure they fit in with the District's long-range air quality plan. But both the mayor and EPA previously supported the additional bus lanes, Rachal said.

The additional bus lanes, none in the downtown business district, were the subject of public hearings last year but were generally ignored in the hullabaloo over controversial bus lane proposals for downtown Washington.

The downtown plan called for making 15th Street one way south as it passes across the Mall and making much of downtown 14th Street one way north. The plan was vigorously opposed by the National Park Service among other groups and city officials are now working on a new downtown bus-lane plan which will make few changes in 14th and 15th Street traffic patterns.

The only vehicles permitted in District bus lanes during weekday rush hours (7-9 a.m. and 4-6 p.m.) are buses, bicycles, motorcycles, taxi-cabs with at least two passengers, cars turning right at the very next intersection and cars stopping "momentarily" to pick up or drop off passengers.

In addition to the new M Street and Wisconisn Avenue bus lanes, the city plans to put new priority bus lanes on:

Georgia Avenue NW, on the west side of the avenue near the District-Montgomery County line. The bus lane would be .07 mile long. A .05 mile long bus lane already exists on the east side of the avenue.

16th Street NW, between U Street and Park Road, 1.8 miles of bus lanes on both sides of the street, to extend the existing 2 miles of bus lanes which extend from U Street downtown.

New York Avenue, NE, .05 mile of bus lanes just east of Bladensburg Road, to assist Metro buses leaving nearby storage areas.

Bladensburg Road, NE, .05 mile between New York Avenue and 26th St., again to assist buses leaving storage areas.

Pennsylvania Avenue SE, adding 2.5 miles from the Anacostia River to Branch Avenue, to the existing 3 miles of bus lanes along the avenue, from the Capitol to the Anacostia River.

South Capitol Street, .27 mile by building a third southbound lane at intersections with martin Luther King Jr. Avenue 1 Street and at Southern Avenue.

13th Street SE, .19 mile, from W Street to Good Hope Road.