Narrative:

Traffic volume was high. Aircraft X was cleared for takeoff on runway 15. Aircraft Y was then cleared for a touch and go on runway 15 behind the aircraft X departure. Aircraft Z was south [along] the 5. Aircraft a was eastbound [along] the ventura freeway and aircraft B was westbound on the ventura freeway. Another helicopter was eastbound transiting as well [along] the freeway.my initial transmission to aircraft B was to follow the ventura freeway westbound. I was already thinking about the possible conflict with aircraft B westbound and aircraft Y and aircraft a eastbound. I departed aircraft X on 15 and shipped him to departure just off the departure end. At that very moment I noticed that aircraft B had not followed by instructions to follow the freeway; but had turned north towards the airport; being a conflict with my aircraft X departure at that very moment; [ground control (ground control)] was in my ear requesting a runway crossing and aircraft C was in my ear requesting a landing clearance. I told aircraft B to turn south towards the freeway with urgency; at that time he told me he was unfamiliar and I saw aircraft X descend under. I saw out the window aircraft B turning; but at no point did I issue traffic to aircraft B on aircraft X departing and visa versa.I started to get busy and the controller in charge (controller in charge) opened assistant local (al). Controller in charge then about 3 minutes later closed; so that he could relieve her on controller in charge to go to a class. Ground control was training. The controller in charge was trying to help me. Two controllers and two supervisors were downstairs. Too much happened at one time and my attention was obviously on the wrong thing at that very moment. I should have asked for the al position to continue to be staffed to assist me.in hindsight after watching the video and listening to the tape; I should have issued aircraft B [the]traffic departing runway 15 and ensured he was following the instructions to remain over the freeway. Had I not allowed the aircraft B to deviate off the freeway this would not have happened.

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Original NASA ASRS Text

Title: Two controllers and three pilots report of a loss of separation due to a Controller not issuing traffic on or before departure.

Narrative: Traffic volume was high. Aircraft X was cleared for takeoff on runway 15. Aircraft Y was then cleared for a touch and go on runway 15 behind the Aircraft X departure. Aircraft Z was South [along] the 5. Aircraft A was eastbound [along] the Ventura freeway and Aircraft B was westbound on the Ventura freeway. Another helicopter was eastbound transiting as well [along] the freeway.My initial transmission to Aircraft B was to follow the Ventura freeway westbound. I was already thinking about the possible conflict with Aircraft B westbound and Aircraft Y and Aircraft A eastbound. I departed Aircraft X on 15 and shipped him to departure just off the departure end. At that very moment I noticed that Aircraft B had not followed by instructions to follow the freeway; but had turned north towards the airport; being a conflict with my Aircraft X departure at that very moment; [Ground Control (GC)] was in my ear requesting a runway crossing and Aircraft C was in my ear requesting a landing clearance. I told Aircraft B to turn South towards the freeway with urgency; at that time he told me he was unfamiliar and I saw Aircraft X descend under. I saw out the window Aircraft B turning; but at no point did I issue traffic to Aircraft B on Aircraft X departing and visa versa.I started to get busy and the Controller in Charge (CIC) opened Assistant Local (AL). CIC then about 3 minutes later closed; so that he could relieve her on CIC to go to a class. GC was training. The CIC was trying to help me. Two controllers and two supervisors were downstairs. Too much happened at one time and my attention was obviously on the wrong thing at that very moment. I should have asked for the AL position to continue to be staffed to assist me.In hindsight after watching the video and listening to the tape; I should have issued Aircraft B [the]traffic departing runway 15 and ensured he was following the instructions to remain over the freeway. Had I not allowed the Aircraft B to deviate off the freeway this would not have happened.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.