POTENTIAL CONFLICT BETWEEN DESCENDING ACR-MLG AND CRUISING UNK VFR.

Narrative

IN 11/88 I WAS CAPT WHEN A TFC CONFLICT INVOLVING AN ACFT BELIEVED TO BE ON A VFR FLT PLAN REQUIRED EVASIVE ACTION TO AVOID A COLLISION. THE FOLLOWING IS A SUMMARY OF THE INCIDENT. FLT HAD DEPARTED PIT ENRTE TO EWR. WE WERE APPROX 30-40 MI NW OF BROADWAY VOR WHEN WE RECEIVED A DSCNT CLRNC FROM FL180 TO 13000'. WHILE DSNDING THROUGH 16700' VFR TFC WAS CALLED AT 12 O'CLOCK AND 3 MI; SWBND AT 16500'. THE TFC WAS SPOTTED IMMEDIATELY AT 12 O'CLOCK AND LESS THAN 1 MI. AT THIS POINT CONFLICT WAS APPARENT. I DISCONNECTED THE AUTOPLT MAKING AN IMMEDIATE LEFT TURN OF 30-40 DEGS AND STOPPED THE DSCNT; AVOIDING A COLLISION WITH SAID ACFT BY APPROX 150' ALT CLRNC AND 1/2-3/4 MI HORIZ CLRNC. AT THE TIME THE MAJORITY OF THE BEVERAGE SVC HAD BEEN COMPLETED; AND THE SEATBELT SIGN WAS ILLUMINATED SUBSEQUENTLY AVOIDING INJURIES TO THE PAX OR CABIN CREW. I REALIZE THAT TFC AVOIDANCE IS THE RESPONSIBILITY PRIMARILY OF THE COCKPIT CREW; HOWEVER IT IS MY OPINION THAT THIS INCIDENT COULD HAVE BEEN AVOIDED BY A MORE TIMELY CALL OF THE TFC BY ATC. ONE CONTRIBUTING FACTOR TO THIS MAY HAVE BEEN CTLR WORKLOAD. THE VFR ACFT WAS APPARENTLY KNOWN TFC TO ATC; HOWEVER WAS NOT POINTED OUT SOONER BECAUSE OF SECTOR SATURATION AT THE TIME.