The room is small. There is a bank of instruments along one wall, a teletype, the faint odor of oil, and a steady ticking noise. Each tick -- one a second -- represents a barrel of gasoline flowing into the Washington area.

Washington receives 90 percent of its gasoline, heating and commericial oil and aviation fuel through two underground pipelines that run 1,500 miles up the eastern seaboard from refineries in Texas and Louisiana.

This complex, somewhat delicate delivery system is a fascinating engineering story. Beyond that, its workings provide clues to some major questions and issues as America faces the worldwide oil shortage.

For example, what if everybody panics as they did during the 1973 embargo and rushes to gas stations to fill their tanks?

"If everybody fills their tanks at once, you pull all the available storage out of the ground," said Alan T. Lockard, chief of the fuels branch in the Department of Energy's regulatory arm. "The service stations run out, and the pipelines, because of their schedules, can't fill the need.

If everyone stays cool, however, Lockard and other experts say consumers can weather the shortage without long lines at the gas pumps simply by cutting their consumption marginally.

One of the keys to this analysis is the pace at which the pipelines can deliver products.

The products fill the pipelines at all times, pushing one another along in "batches" at five or six mph to be tapped off into bulk storage terminas at 100 or more locations along the way.

The batches remain reparate from one another in the pipeline with little mixing. In a line 30 inches in diameter, a 25,000 barrel batch of, say, jet fuel, fills 5 2/3 miles of pipe. For a 12-inch pipe, this would be 34 miles.

The order of the batches is carefully programmed so that unleaded gasoline will not be contaminated by leaded gas. A batch of one product, such as commercial heating oil behind a batch of leaded gas, will "wash" the pipe of lead, for example.

Each batch belongs to a specific oil company when it enters that pipeline from a refinery, and that same batch is delivered to the same company at the tap points. Each company is responsible for having adequate storage at the tap points to take the oil when it arrives.

At the rate the petroleum travels through the pipeline, it takes about 1/ days for a batch of "product," as it is called by the terminal operators, to reach the Washington area from the Gulf of Mexico area.

Two of the tap points along these pipelines serve the Washington area from suburban Virginia -- one at Newington south of the Beltway, another north of Fair City Mall in Fairfax City.

At Newington, in the control room, with its steady ticking noise, is the equipment monitoring Plantation Pipe Line Co.'s tap point.

Exxon, Shell, Amoco, Cities Service, Texaco, Gulf and Crown have bulk storage or "tank farms" located at these two tap points. The storage holds 15 to 30 days' supply of petroleum products for this area.

Each day hundreds of tank trucks holding up to 8,000 gallons apiece fill up at these tank farms and then fan out across metropolitan Washington, delivering to gas stations, homes, apartments and commercial buildings.

Small auxilliary pipes run from these tank farms to Dulles and National airports, carrying aviation fuel that is then stored in Smaller tanks until sold to the airlines.

Some major oil companies do not own tank farms in this area, but they have contracts to share capacity in the tank farms of companies here.

Other companies with tanks in Baltimore truck gasoline and oil products down from there to this area. There are three major tank farms in Baltimore supplied by taps from Colonial Pipeline Co., the larger of the two pipelines running through this area, and by tanker ships that bring refined products up the Chesapeake Bay.

Steuart Petroleum, a local company that is one of the largest suppliers of heating and commercial oil here, brings itsd product up the Potomac on barges and keeps it in two tank farms on the Anacostia River.

"It's amazing how delicate the (supply system) balance is in the whole industry, said J.K. Richmond, a stout, businesslike man who runs Exxon's terminal at Newington. "We have 34 million gallons of storage here. That sounds like a helluva lot of product, but that might only constitute an adequate 15 day supply (for the Washington area.)"

Exxon claims about 20 percent of the Washington area gasoline market. It has about 450 stations here, all of them supplied by track from Richmond's terminal.

Richmond supervises 15 of the giant storage tanks, each is assigned a specific product -- lead-free gasoline, No. 2 heating oil, aviation gasoline, and so on.

Like the gas tank of your car, these tanks are full just after a delivery, then gradually they empty. Depending on demand, they can get very close to the bottom before another delivery from the pipeline comes.

Nearby, Shell has a similar facility -- 10 tanks with a total capacity of about 21 million gallons. Shell serves about 165 stations in the area from this terminal. The terminal manager, H. G. Tulbert, said the tanks hold about a 30-day supply.

Crown Central Petroleum Corp., a medium-sized refiner with headquarters in Baltimore, has the third tank farm at Newington.

Crown's tank farm is smaller than the other two, and sells a higher proportion of its product to independent wholesalers -- middlemen called "jobbers" in the oil business -- than do its neighboring giants.

Exxon, Shell and the other big companies own their own fleets of delivery trucks. The jobbers deliver to the smaller chains and independently owned stations.

Plantation's small terminal building is located about midway among the three tank farms. This is the end-point for the entire Plantation route stretching from Baton Rouge, La.

Outside the building, the 12-inch diameter pipe curves up from the ground and loses itself among a spaghetti-like arrangement of pipes.

This is a manifold where the one Plantation pipe meets at least four outlet pipes -- one for each of the tank farms and one to a "dumping tank" where several hundred barrels of product that mixes between batches in the pipeline is placed to be reprocessed in a refinery.

When Plantation's manager there, Carl F. Sorrow, has finished delivering a batch to one customer, he or his employe, called an operator, press buttons that switch delivery on the manifold to another outlet.

The Colonial pipeline is much bigger than Plantation's. It is 32 inches in diameter when it arrives here, and it goes on north to New Jersey.

Colonial's manager, Jim Golay, can deliver 20,000 barrels of product an hour at his terminal, located at the end of a 22-inch pipe that runs to Fairfax City from Colonial's main 32-inch pipe.

Sorrow can deliver at about 4,000 barrels an hour. A barrel is 42 gallons.

Industry sources say it costs about a penny and a half a gallon to get product tere by pipeline, and another half penny a gallon to deliver it by truck from the tank farm to the consumer.

DOE keeps oil product consumption figures by state, but not for the Washington area as a whole. Last December, for example, District of Columbia drivers used 411,000 barrels of gasoline of all types. Maryland drivers used 4.1 million barrels that month and Virginia drivers 5.8 million barrels.