Despite South Africa's precarious oil supply situation, motorists here have not had to wait in line for gas, largely because of the government's persistence on conservation.

The most drastic measure was to drop the national speed limit from 54 miles an hour to an incredibly boring 42 miles an hour, even on expressways. One American swears he saw it least two drivers reading books as they drove along a highway.

Except for an outcry from truckers and criticism from the automobile association, which said its tests have shown 48 miles an hour would be more realistic, South Africans have accepted the new speed limit with minimal grumbling.

The authoritarian government, immensely more immune to the vagaries of public opinion than Washington, also raised the price of gasoline to $2.64 a gallon. Stations are closed on weekends and after 6 p.m. week nights.

These measures have forced down gas consumption by more than 25 percent, according to one source. The government has not confirmed the figure.

Last May, to save diesel fuel, the then economic affairs minister Christian Heunis ordered agriculture industrial and transport leaders to come up with voluntary conservation plans that would cut consumption by 20 percent.

About 400,000 consumers in these three sectors are being monitored by the government, and if they do not meet their promised reduced levels, the government reportedly will order the oil companies to cut their supplies.

Although Heunis said oil imports decreased by 40 percent in the first quarter of this year because of the Iranian production cutoff, officials maintain they did not have to dip into strategic reserves to compensate.

The government's greatest worry is that conservation and price measures may stunt economic growth and boost inflation -- which could reach 15 percent this year.