Montgomery County's new bikeway master plan calls for 331 miles of bicycle paths in parks and bike lanes on county roads, five times the size of the somewhat disjointed system of bike routes in the county today.

The network of bicycle paths planned for most developed sections of the county will give Montgomery one of the most extensive systems of bike paths presently planned for the Washington area.

Only Arlington has mapped as many future bike routes. The two counties also lead the area in trails already constructed. Fairfax County and Alexandria have almost no bike trails and few long-range plans for any. The District and Prince George's county have adopted bicycle master plans but have yet to construct many bike routes.

However, the 331-mile system of bike trails may not be completed for at least another 15 to 20 years or longer, since the county has drastically cut funds for bike-trail construction. The county and its planning agency would have to spend $380,000 a year to complete the system by 1993, according to county estimates.

Montgomery spent more than $400,000 a year on bike trails in fiscal 1975 and 1976 and will spend $421,800 this fiscal year, much of it going to fill some of the gaps in the 60 miles of existing county bike trails. An additional $150,000 will be spent by the Maryland National Capital Park and Planning Commission.

But county bike funds, have been cut back by 70 per cent, to $129,000, during the coming fiscal year, whiich begins in July, and no bike funds at all are programmed for 1980 and beyond, says John T. Clark, assistant director of the county's transportation department.

The Park and Planning Commission, which oversees county park land, now expects to maintain a $150,000 a year fund for bike trail projects. That amount is half of the $300,000 a year that the commission announced two years ago would be the annual bicyle appropriation.

The new master plan, officially presented at a public hearing two weeks ago, shows few long bikeways in the county today. The longest is along MacArthur Boulevard, which last fall was extended to the District line. Shorter bike paths - also separated from street traffic - exist along sections of River Road, Old Columbia Pike and New Hampshire Avenue.

The most popular bike path in the county is on the National Park Service's unpaved C&O Canal towpath, which has 37 miles in the county and extends 184 miles from Washington to Cumberland.

The county's bikeway master plan came in for minor criticism recently from the National Capital Planning Commission, however, because the proposed trails are not all coordinated with bike trails planned in the District or on federal facilities like the National Institutes of Health and National Naval Medical Center in Bethesda.

The District, for example, plans a major commuter bike path along Massachusetts Avenue, using sidewalks, but the path would end abruptly at the county line since Montgomery has no bike route of any kind planned along Massachusetts Avenue.

Most future bike trails identified in the master plan will be built in streamvalley parks in the county, including Rock Creek, Cabin John, Sligo Creek, Paint Branch, Piney Branch, North Branch and Northwest Branch.

Under the master plan there will be 188 miles of "class I" bike paths or trails, paved and completely separate from roads. The county now has 29 class I paths. Most will be built by the Park and Planning Commission but some will built in conjunction with sewer projects - the county's large collector flowing to the Blue Plains sewage treatment plant.

There are to be 48 miles of class II bike lanes. There are now 20. They will be built along existing roads, usually on the road shoulder but separate from traffic. The recently paved shoulder of New Hampshire Avenue is a class II bikeway, although no signs yet designate it as such.

The county has not yet completely endorsed the concept of class III bike trails, where signs are posted along certain roads to encourage their use by bikers and to warn motorists of heavy bicycle traffic. The bicyclists mix with traffic as they do on streets where there are no adjacent bike paths.

Ont only mile of Class III bike route has been designated, although 16 additional miles are programmed and a total of 46 shown on the master plan. The master plan also projects 49 additional miles of bikeway but does not designate what type.

Much of the future bikeway building in the county is expected to come only with park sewer projects or in state or county highwya projects that reconstruct roads appearing on the bikeway master plan, say county planning officials. They will be funded with county, state and federal highway funds. Both county and state highway departments are now required to consider including bikeways in all road projects.

The major county bikeway projects during this fiscal year include the Montgomery Village bike paths, built along 25 miles of the development's main road, on both sides of the street; the extension of MacArthur Boulevard's bike path to the District line, and two miles of class I bike path along Falls Road near Great Falls, which by 1979 will connect the MacArthur Boulevard and River Road bike trails.

Park and Planning Commission bikeway construction this fiscal year includes some trails in Rock Creek and Sligo Creek Parks, and along Long Branch Parkway in Takoma Park.