Each passing week, the Soviet Union appears more and more like a speeding bus headed toward an abyss while the passengers and driver argue over who owns the vehicle, how fast they are going and which way to turn the steering wheel. Catastrophe may happen before the dispute is resolved. Or somebody may hijack the bus at gunpoint and take it somewhere equally disastrous.

In the midst of this crisis, which is both political and economic, President Mikhail Gorbachev is fighting for his political survival. While he has plenty of critics both inside and outside the Soviet Union, Gorbachev still seems to offer the best chance for finding some middle course between supporting fledgling movements toward democracy and holding the country together.Even now, the Soviet bus may be so far out of control and the dissident voices on the right and left so severe that Gorbachev cannot avoid either personal or national calamity. Consider the extent of the problems:

- Ruined by more than 70 years of communist rule, an arms race with the West while stirring up trouble internationally, the inability to feed its people, and a centralized, subsidized production system paralyzed by bureaucracy, the Soviet economy has reached the point of collapse.

- In the first quarter of this year alone, Soviet foreign trade fell by a third, the gross national product shrank 8 percent, productivity dropped by 9 percent. Chronic shortages, always a problem, persist with the added problem of vastly higher prices for the most basic consumer goods.

- Gorbachev has pushed for free market reforms. But the early going in a transition from a broken-down communist system to a free market can be traumatic. In addition, the half-measures adopted so far have left the Soviets with some of the worst features of both socialism and capitalism.

- Former captive East Bloc nations have turned to the West for trade and economic help. As a result, Soviet trade cannot cope in the international market. Hard currency foreign debt has more than doubled to $47 billion since 1984 despite heavy production from Soviet gold mines. The USSR is now in debt to many countries, including such former satellites as Hungary and Czechoslovakia.

- Despite its name, the Soviet Union has never been a unified nation. It was formed and held together by force. Democratic reforms have caused many Soviet states and ethnic groups to take radical steps toward independence. This has threatened governmental chaos and hurt the already ailing economy.

- Fed by dissident movements and economic problems, strikes have broken out all over the country. A third of the USSR's coal miners have been off the job for eight weeks. Demands for pay hikes have evolved into political demands, including the resignation of Gorbachev and the repudiation of communism.

Gorbachev's latest move toward a free market economy, including privatization of one-third of all small business, is based on a program that combines limited reforms with strict discipline, including the outlawing of strikes. But some critics want an immediate, wholesale transition to a market economy, saying half measures only prolong the agony.

Kremlin leaders say the country is in danger and that democracy cannot exist without discipline. The alternative is chaos. They have a point. Chaos may invite armed repression by hard-liners and the military, and perhaps even the fall of Gorbachev.

Observers say Gorbachev's government already appears paralyzed and unable to exercise full political control.

As a result, U.S. officials have begun broadening contacts with their Soviet counterparts at various levels of government just in case Gorbachev does not remain in power.

The next months will be fateful ones for the USSR and the entire watching world.