Light Transport; Low Wing; 2 Turbojet Eng
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 6
Situational Awareness; Time Pressure
Conflict NMAC
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Took Evasive Action
Human Factors; Procedure; Airspace Structure
Aircraft X was cleared for the ILS RWY 19 approach by NY TRACON (MUGZY). He was changed to my frequency (TEB Tower; 119.5). Upon initial contact; the Collision Alert alarm alerted me of a VFR target approximately 2 miles south of Aircraft X's position; transitioning in block of airspace that cuts directly through the final for the ILS to Rwy 19. Traffic was issued to the only aircraft I had on frequency (Aircraft X) and he was instructed to 'descend if necessary' to avoid a collision. Aircraft X picked up the traffic at approximately one half mile of horizontal separation with only 100 feet of vertical separation. Aircraft X was instructed to descend immediately to avoid traffic. At the same time; the unidentified VFR target (later identified as Aircraft Y by the Aircraft X pilot) also began to descend; putting both aircraft at the same altitudes as targets merged at 6 mile final for runway 19. Aircraft X passed behind Aircraft Y and landed without incident. Aircraft Y later picked up flight following with N90 (HAARP/LGA sector) and his tailnumber was identified as Aircraft Y. As the pilot technically didn't violate any airspace; his tailnumber and type were only recorded for the purpose of this safety report.The airspace to the north of Teterboro is an uncontrolled VFR corridor that allows aircraft and helicopters to transition 5 miles north of the airport without any radio communication with Teterboro Tower or NY Tracon (N90). This incident is one of many that clearly illustrate the need for that airspace to be controlled by either facility; as it is a busy transition area for aircraft and helicopters enroute to the Hudson River. Teterboro very easily could be granted a radar assist position and given the airspace to the north of the airport to properly control the VFR traffic altitudes as it passes through the final approach course for runway 19. Continuing to let this area of airspace be uncontrolled is dangerous.
TEB Tower Controller reported of a NMAC between an aircraft under ATC control and a VFR aircraft. Reporter stated this is in the vicinity of an uncontrolled VFR corridor and is a very busy transition area. Reporter would like someone to control this area to help avoid conflicts.