The average speed of motorists traveling on Maryland highways is 58 miles per hour -- faster than any other state in the nation, according to the preliminary findings of a government survey released last week.

However, the Maryland State Police and the Highway Users Federation, which compiled the results over the first half of fiscal year 1982 for the Federal Highway Administration, say the study is no indication of the state's effectiveness in enforcing the national 55-mile-an-hour speed limit.

"The data does not cast any doubt on Maryland's present campaign to crack down on speeders," said Jack C. Martin, federation spokesman.

The survey showed the average speed of highway motorists nationwide between October 1981 and March 1982 was 55 mph. Eight states, including Maryland, were found to be in the 57 to 58 mph range. All figures will be adjusted in September to account for speedometer variability and deviations in the monitors that are used across the country to keep track of speeders.

State police spokesman Dan McCarthy was not particularly alarmed by the data, explaining, "If people are going 57.9 mph , it shows they are complying with the spirit of the law."

Martin said the state's top ranking for average highway speed may be attributed in part to the relatively low number of 55 mph roads in the state serving as the basis of the survey.

The number of motorists who travel at speeds of 65 mph or greater, which was not included in the data, is a more meaningful statistic, according to McCarthy, since a greater number of accidents occur at higher speeds.

Since last October, the number of motorists reported traveling 65 mph or faster in Maryland fell from 13.8 percent to 5.3 percent. Nationally, the proportion of motorists monitored at those speeds is 8 percent.