Transportation Secretary Brock Adams has sent a major legislative proposal to the White House that, among other things, would force states to decide by 1982 whether to complete their segments of the interstate highway system.

The proposal, according to authoritative sources, would also reduce the advantage highways have over public transit in competing for federal dollars, and would give local governments in the nation's 25 largest urban areas more control in deciding between new highways and other modes of transportation.

The result of weeks of meetings involving Adams, key aides and state transportation directors, the proposal was delivered to the White House and the Office of Management and Budget over the weekend. Adams hopes to have a firm Carter administration position ready to present to Congress by January.

The amount of federal money for transportation would not increase significantly between now and fiscal 1981, when Carter has promised to give the nation a balanced budget. The current budget has $10.8 billion for transportation; the proposed fiscal 1979 budget would have $11.8 billion; a total of $11.9 billion is projected for fiscal 1980.

But Adams would make significant changes in how that money is divided and how much control local control is exercised, particularly in major urban areas.

The interstate highway program is a key element in the redistribution plan. About 90 per cent of the 42,500-mile system has been completed and another 5 per cent is under construction. But as long as there are gaps in the system, all 50 state highway departments get a certain amount of interstate money.

Under Adam's proposal, those states with missing links would have to either complete enviromental impact statements on construction by Sept. 30, 1982, or request that the money by made available for something else.

Interstate highways are built with nine federal dollars for each state dollar, but urban mass transit systems are built on an 80-20 basis: one state dollar brings in only four federal dollars for a subway.

Because of that, states that would be inclined to replace freeways with subways, buswsayss or trolleys have often opted for the freeways.

Part of Adam's plan would preserve the 90-10 split for transit projects and other, lower-priority highway programs if a proposed interstate highway is killed and the funds diverted.

A potentially controversial proposal would shift decision-making on the use of urban highway funds from state highway departments to local agencies designnated by the governor and the localities.

Such a change would make it easier for urban governments to opt for transit instead of rural-supported highways, for example, but it would also antagonize the congressional road lobby and the statehouses.

Adams repeats his strong support for a mass transit trust fund, financed by a tax on energy. If that is not possible, he proposes advising state and local governments at least one year in advance about what the federal contribution to transit will be. A lack of certainty about such funding is a frequent complaint of transit managers.

Adams also urges that planning money for highways and mass transit systems be combined and that, ultimately, all surface transportation programs operate out of the same agency and under the same legislation.

Today, highway funds come from the Federal Highway Administration and transit funds from the Urban Mass Transportation Administration. While both offices are part of Adams' department, authorizations and appropriations are handled differently in Congress and the total transportation program is rarely viewed as a whole.