he elevated trackways that its trains clatter along are so old they have been proposed as official historic landmarks. It has the highest base fares in the country, yet in practical terms is bankrupt, stalling its creditors and cutting service. Its managers must juggle the often conflicting political goals of governor, mayor and the ordinary people who depend on public transportation.

Despite it all, the Chicago Transit Authority (CTA) stays in business. In the past year, the bus and rail system has stumbled though one of the worst financial crises to hit any U.S. public transit system in recent years. For the present, it has a few months' breathing space as the city government injects emergency funds, but the long-term bailout it needs remains as elusive as ever.

In some periods of its history, Chicago was a pioneer in providing affordable transporation for its citizens--horse-drawn omnibuses appeared on the streets in 1852. Today, the city is a case study in how the inflation and political constraints facing all U.S. transit systems can lead to a destructive spiral of increased fares and decreased service that in the end drives people into private cars.

The base fare for CTA's buses and trains is now 90 cents, a national high. Add a transfer (as most riders do) and the cost is $1 even. "The service is not really worth the fare," complains Joanne Anderson, a hospital technician encountered in a downtown rail station recently.

On an average weekday, about 800,000 people take some 2 million rides on CTA buses and railcars. At rush hour, about 2,100 buses are on the streets and 900 railcars on 192 miles of track. Many trains run the famous "L" lines, twisting and turning over the streets of downtown Chicago on elevated trackways built in the 1890s.

CTA was created in 1947 by the Illinois state legislature to consolidate a collection of rail, streetcar and bus lines left in financial shambles by the Depression. In the early 1970s, feeling the pinch of Vietnam War inflation, CTA turned to the state government for help in meeting operating expenses.

But by the late '70s things had worsened markedly, as accelerating inflation struck particularly hard at transit costs. Fuel costs climbed and wages of the strongly unionized transit workers grew well ahead of average rates. By 1980, CTA's operating costs had climbed to $514 million, 187 percent higher than 1970's figure, though service remained essentially the same.

Government subsidies in the same period grew from zero to $259 million.

With politically unpopular fare increases unable to keep pace with rising costs, things came to a head early this year, and CTA found itself effectively bankrupt.

CTA Chairman Eugene Barnes began warning that if help wasn't found the system could close soon. Meanwhile, trains and buses stayed in operation, but only because maintenance was deferred and payment stalled on routine bills--pension and insurance contributions, bus-tire and electricity contracts, for instance--to reserve funds for payrolls and fuel, the two items that would close things down immediately if left unpaid.

In March, cash was so scarce that CTA paychecks went out with insufficient funds in the bank to cover them. Disaster was averted by a courier who rushed to Springfield to pick up a subsidy check that got to the bank one step ahead of the paychecks.

Straightening out public transit has long been an important political issue in the city. Now it emerged as a contest between Republican Gov. James Thompson and the city's Democratic Mayor Jane Byrne. Byrne had her city to keep happy; Thompson stood to score points in the state's major voting and tax district.

Last spring, Thompson proposed taxing oil company revenues by 5 percent to subsidize CTA and other Chicago-area transit systems and making immediate loans of hundreds of millions of dollars. When that failed, Thompson proposed raising state sales and liquor taxes. That one died too, while Mayor Byrne charged that neither plan was generous enough anyway.

The problem was that "downstate" legislators, already facing Reagan's plans to cut federal aid to the states, balked at giving CTA more money, arguing that after a decade of subsidies its deficits were only growing larger. Many saw it as overstaffed, extravagent with its unions (bus drivers earn a top wage of $12.41 an hour) and an endless drain on the taxes of people who never use it.

During the summer, Byrne declared that if the state would not save CTA, Chicago would go it alone. The city council pledged up to $100 million for CTA this year, applying new taxes on city commerce. Sales and cigarette taxes rose and a controversial 1 percent tax on services--including fees of doctors, lawyers, architects and barbers--was approved. (The latter tax is now tied up in court.)

Byrne's package also created a special board to oversee the bailout. With 10 of 13 members appointed by the mayor, the board was widely seen as a tool to consolidate city control over CTA, an important unit in city politics and the employer of 13,000 people.

At the same time, layoffs and service reductions began. In September, seven bus routes were eliminated and service was reduced on 58 others--a move Byrne says will save $12 million annually. Rail cuts are planned for December.

Last month Byrne fired all 107 members of CTA's security force, saying the Chicago police and private guards could fill the gap. This month, 97 bus drivers and 103 administrative workers are scheduled to be laid off.

However, by all accounts, these amount to only one more temporary fix. "There is a point of diminishing returns," Byrne said in remarks prepared for the annual meeting of the American Public Transit Association. "Once systems have been pared to the bone, then further service cuts and fare increases begin to drive away riders and employers and to deny service to those truly in need."

For long-term help, Chicago continues to look to the state and the federal government, but their assistance is uncertain. Though it continues to cover most of the costs in CTA's purchase of new buses and railcars, the Reagan administration plans to phase out operating aid altogether.

State funds will be increasingly stretched as federal spending is cut back. With the 1982 election drawing near, state legislators are expected to become more anxious to appear thifty. Moreover, a pending reapportionment will eliminate many of the legislators' seats, making competition for votes that much fiercer.

Among the system's riders, some people are angry that service reductions come even as fares continue to climb. Clothing store manager Bob Taylor, catching a train from a downtown "L" station, pointed to New York City. "If they can have 60-, 70-cent rides, why can't Chicago?" he asked. Others, like Keith Moak, an advertising firm employe, believes it's only fair that users pick up the costs. "They have to sock it to the Chicago residents," he said.

Revenue rose after the last fare increases in July; ridership, predictably, did not. CTA spokesman Bill Baxa said it is now about 11 percent lower than a year ago. Meanwhile, highways leading downtown are reported more congested, as commuting by car becomes the cheapest way to go for growing numbers of people.

Many officials believe that gradual deterioration of service is unavoidable. For instance, external affairs director Joby Berman noted that payments are in arrears on a bus-tire contract with Goodyear, which has curtailed deliveries in response. "If we have a bad week, and we need more tires than are available, then buses don't go out," she said.

For the moment, however, warnings of imminent closure have ceased, and CTA stumbles onward. But those warnings do not appear to be a case of crying wolf. Public transit in Boston and in Birmingham, Ala., stopped running temporarily this year due to money problems, and Chicago, facing a similar squeeze, could one day be added to the list.