Yellow police call boxes, which have worked on and off along the Maryland Capital Beltway for the past 10 years, will be removed by state highway officials because fewer than two-thirds of them functioned at any given time.

Instead, Maryland hihgway Administrator Slade Caltrider said the wide use of CB radios and regular police patrols would provide disabled motorists the same service.

Ever since the first 264 call boxes were installed with great fanfare at quarter-mile intervals along the Maryland portion of the Beltway, they have frustrated state police with frequent false signals and occasional calls by motorists asking directions to their destinations.

In addition, Caltrider said replacement parts have become scarce for the experimental microwave-powered system and technicians have had to "cannibalize" the system to keep some boxes working: About 170 of the original 264 boxes are still in service.

"They just weren't that reliable," said Caltrider, who was previously the highway departments' district engineer in Montgomery and Prince George's counties. . "They created a lot of frustration for police and motorists. A lot of times a motorist would push a button and a transmission wouldn't be made. Or they would push a service button when they wanted an ambulance, or vice versa"

The help signal is transmitted from the boxes to state police barracks in Rockville, Forestville and Greenbelt, where receivers display the number of the call box and the type of help needed.

But Rick Jacoby, a state police dispatcher in Rockville, said many police consider the system "a pain." "Most of the time they'll get to the box and nobody will bethere, and the signals break up radar."