By the end of the summer, Capital Beltway motorists who travel between Virginia and Maryland will confront a confusing sequence of exit signs.

The Maryland State Highway Administration is renumbering its exits in Montgomery County along the Beltway, also known as Interstate Rte. 495. The changes in numbers, to be completed within a few months, will mean that a traveler crossing into Montgomery County from the I-495 and Interstate Rte. 95 interchange will find the first exit to the west, onto New Hampshire Avenue, marked exit 28 instead of exit 25.

The exit numbers will continue through the county, calculated on a mileage basis, through exit 41, which is to the George Washington Parkway in Maryland.

Exit signs in Prince George's County were renumbered to from 2 through 27 earlier this year, Maryland highway officials said. Formerly, the exit numbers ran from 26 through 38. So in a few months, a motorist who leaves Virginia by crossing the Potomac River via the Woodrow Wilson Bridge into Maryland will find the exits numbered from 2 through 41 if he continues around the Beltway to its westernmost point in Montgomery County.

In Virginia, it will be at least a year before any new renumbering system is begun on the state's part of the Beltway, according to Don Keith, resident engineer of the Virginia Department of Highways and Transportation. Virginia's Beltway exits now number 1 through 14.

Keith said that within 12 to 18 months work is expected to begin on signs and traffic management systems for the Beltway and Shirley Highway in Virginia. It has not been determined what numbering system will be used, he added.

Under the system, a motorist who leaves Virginia and crosses the Potomac River into Montgomery County, does so after passing Virginia exit number 14. Under the old system, the first exit he reached in Montgomery was numbered 15; under the new, it will be 41.

To lessen the confusion, directional signs at each Montgomery County Beltway exit will include both the old and new exit numbers for about a year, according to William J. Carlson, assistant district traffic engineer in Maryland. The old exit number will be attached to a black-on-yellow sign reading "old."

Maryland officials said the new numbering system will help both motorists and police in reporting and responding to accidents. A milepost numbering system permits a quick determination of the precise location of an accident, they said.

It will mean that new exit number 17 in Maryland is about 17 miles from the Woodrow Wilson Bridge, for example, Carlson said. The system, called "log-mile reference," is common other parts of the country, highway officials said.