For two hectic days Cambridge drivers have been experimenting with Harvard Square's new traffic circulation plan, but it is still unclear whether the new system will be a boon to motorist or an invitation to even more congestion.

Officials of the City Traffic Department are optimistic, and they say that the first days have worked out better than expected. But yesterday there were still dozens of cars, surprised by streets that have suddenly become one-way, moving against the flow of traffic.

One local resident who teaches at Brandeis said yesterday tha he plans to leave his car in the garage for the next few weeks. "I just can't cope with this ridiculous new plan," he said.

According to a district supervisor of the MBTA who was standing vigil at the Square during rush-hour yesterday, the buses are having no trouble with the new system. But the passengers are somewhat less pleased. "For 15 or 20 years the Belmont bus has left from that spot right there," one irritated passenger said, "and now I haven't any idea how to find it."

Most taxi drivers in the Square also seem to be disappointed with the rearranged traffic pattern. Some have had to turn away fares because the complicated network of one-way streets makes it almost impossible to get to certain parts of Boston without going miles out of the way.

Much of the difficulty with the new system will probably disappear once drivers have a chance to become familiar with the changes. The situation also may be improved when the second half of the new plan goes into effect in two to three weeks. Drivers heading south on Mass. Ave, are now able to go straight into the Square, but soon they will be forced to leave Mass. Ave, at Waterhouse Street and turn down Garden Street.