While the 55 mile-per-hour speed limit has been credited with reducing fatality rates on modern highways, drivers who use older roads have not reaped similar safety benefit, according to the Road Information program.

In 1974 the first year of the nation-wide reduced speed limit, fatality rates on the Interstate Highway System in Maryland dropped 33.5 per cent, and increased 1.9 per cent on local roads and streets, a road information spokesman said.

Nationally, fatality rates on the interstate highway system dropped 32.6 per cent, compared with a decrease of only 1.6 per cent on local roads and streets. Rates have remained in proportion since then, the spokesman said.

One National Highway Traffic Safety Administration study on the safety benefits of reduced speed limits found "the high speed highway systems experiencing large savings and the local type rural roads showing no improvements."

The American Association of State Highway Transportation Officials studied the 55 m.p.h. speed limit and concluded that "roads with the highest design standards have the lowest accident and fatality rates," the spokesman said.

Howard L. Anderson, associate administrator for safety at the Federal Highway Administration, points to the interstate system as "probably the most outstanding example of the impact of good roadway design on highway safety." He credits the system with saving 60,000 lives since 1956, when the first miles were opened.

But even when complete, the Road Information program reports, the proposed 42,500-mile interstate system will comprise only 2.3 per cent of the total 1.8 million miles of paved roads in the nation. Of the total, they report , 800,000 miles have problems which can affect safe driving. Bumps, ruts, potholes, broken pavement, shoulder dropoffs, blind curves, narrow lanes, steep hills and obsolete bridges are among the most common hazards, they warn.

Giving too much credit to the 55 mile-per-hour speed limit may lull some drivers into thinking they can be less careful on local, low-speed roads when just the opposite is true, Reece said."It may also tempt some drivers to speed on back roads where they think laws are not enforced," he said.