Arlington Boulevard (Rte. 50), one of the more heavily traveled commuter routes in the area, is by far the most dangerous road in Fairfax County, according to a list of the 50 most dangerous intersections released yesterday by county police.

Three of its intersections -- those with Gallows Road, Patrick Henry Drive and Annandale Road -- were among the four most frequent accident sites in the county last year, with the Gallows Road intersection near Fairfax Hospital ranking first and Patrick Henry Drive in second place.

There were 134 accidents at the three locations, a tenth of the 1,350 that occurred at all 50 intersections.

"Rte. 50 is a primary east-west artery, especially at rush hour, and the problem is you also have the heavy secondary crossroads, and its just two heavy flows meeting each other," said police Capt. Luther Nossett, who commands the Mason District substation.

Improvements are under way or planned at all three intersections.

There were 48 accidents at Arlington Boulevard and Gallows Road last year, including 17 that resulted in injuries.

The intersection ranked 14th in number of accidents in 1983, and police said construction there to make the intersection safer probably is making it temporarily more dangerous.

An overpass and cloverleaf are being built to separate the roads.

Arlington Boulevard at Patrick Henry Drive, which was first in 1983 with 55 accidents, slipped to number two this year, with 47.

There were three fatalities last year among the accidents at the 50 intersections, the same number as in 1983.