Secretary of Transportation Brock Adams yesterday warned Maryland and the District of Columbia that their enforcement of trucking weight laws is "marginal." He also threatened to cut off federal highway aid to 16 states for inadequate enforcement.

In letters to governors of the 16 states, Adams gave them 45 days to show why federal highway construction money should not be stopped.

Officials of DOT told a congressional hearing that there is evidence the states are not properly enforcing the laws. They cited too few weighing scales, too few spot checks of trucks and failure to levy fines on violators.

Because of damaged roads, truck overloading has become an issue before a House Ways and Means subcommittee, which is studying gas taxes that finance the highway trust fund. One topic is whether truckers pay enough taxes, given the potential damages to highways.

DOT officials said letters warning of a cut off of funds went to Rhode Island, Pennsylvania, Hawaii, South Dakota, Delaware, Nevada, Wyoming, Alabama, North Dakota, Arizona, Massachusetts, Conneeticut, Maine, New York, New Jersey and Oklahoma.

To 11 other states and D.C. Adams warned of "marginal" enforcement today. The states were West Virginia. Maryland, Iowa, Mississippi, Vermont, Texas, New Hampshire, South Carolina, Alaska, Kentucky and Georgia.