President Reagan appears to be in a position to throw the switch that could keep the nation's trains rolling after 10:30 p.m. on July 11.
Contract bargaining between carriers and the Brotherhood of Locomotive Engineers (BLE) is deadlocked, particularly over extra pay for crews on runs that exceed 100 miles. The union is poised to strike nationwide on Sunday unless the President decides to bar such action for 60 days - a decision his predecessors in the Oval Office have made reluctantly during other rail disputes.
A strike could cripple virtually all rail service except Conrail, the quasi-governmental freight and commuter system in the Northeast, and a part of the Amtrak passenger rail system.
An order for a ''cooling off'' period, during which a presidential board would study contract talks and recommend possible settlements, would be the last step in slow-moving negotiations under the federal Railway Labor Act. Railroad unions have criticized that law as interfering with collective bargaining.
President Reagan apparently has no philosophical qualms about using the strike-delaying power given him by law. Although White House sources said on July 7 that ''no decision has been made yet'' on action to bar a walkout, the President is reportedly ready to do so.
However, timing of the rail crisis is bad for a President who is anxious to improve relations with organized labor.
Moreover, should renewed bargaining fail to bring an agreement within the 60 -day period, the rail stoppage would be shifted from mid-July to Sept. 11, a time of heavy Labor Day travel.
With Railway Labor Act procedures exhausted, the administration's only recourse would be to ask Congress for special legislation to bar a railroad strike, a move that would be unpopular two months before congressional elections.
Although the BLE strike threat is the principle worry now, the United Transportation Union (UTU) is threatening a more limited walkout July 30 against three carriers - expected to be the Atchison, Topeka & Santa Fe, the Chesapeake & Ohio-Baltimore & Ohio, and the Southern Railway.
The BLE represents 85,000 conductors, trainmen, switchmen, brakemen, and yard workers employed by 117 railroads.
Six other unions negotiated settlements with the railroads last November for 25 to 30 percent in wage and cost-of-living gains over the next three years. This became a pattern for settlements with five other unions, leaving only the BLE and UTU without new contracts.
These unions, the strongest in the industry, contend that the National Railway Labor Conference, which bargains for industry carriers, has held up similar wage settlements in efforts to win concessions on work rules.
Railroad negotiators have been fighting for years to end what they contend is an ''antiquated'' rule that gives extra pay for traveling more than 100 miles a day, a provision written into contracts when steam engines averaged 12 miles an hour or less.
Unions that have balked at the changes now say that the carriers are refusing to extend wage settlements with other unions to the BLE and UTU unless the two make money-saving concessions to the carriers.
The last nationwide rail strike, by signalmen, was in 1971 and lasted two days. A limited strike against one railroad in 1978 spread to five other carriers and eventually affected two-thirds of all rail traffic over a two-week period.