Commercial Fixed Wing
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 3
Communication Breakdown; Confusion; Situational Awareness
Deviation / Discrepancy - Procedural Clearance; Ground Incursion Taxiway
Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance
Environment - Non Weather Related; Human Factors; Airport
I was providing on the job training on Ground 1 when the following event happened. Aircraft X exited [Runway] 25R at J and was instructed to 'taxi via B; L; hold short of K1 and contact City Ramp.' Aircraft X read back the instruction correctly. The developmental made two more calls and in the meantime Aircraft X started to turn from B onto K...one taxiway earlier than instructed. I pointed out the error to the developmental and then the developmental immediately told Aircraft X to stop. (Background: K & L are now City Ramp controlled and the only entry point to the ramp without additional coordination is via L short of K1.)We explained to Aircraft X that they were prematurely turning into the ramp and not following the issued route. Aircraft X responded by saying they had received clearance to continue on K short of K2; however we had never mentioned anything about K/K2. The Controller in Charge coordinated with the City Ramp via the phone and verified that it was safe for Aircraft X to continue northbound on K. Additionally; while this entire scenario was unfolding; Aircraft Y deviated from their taxi clearance (B; K; C; Northroute) and turned onto L. I overkeyed the developmental and told Aircraft Y to 'hold short of K1 and contact the ramp.' After the training session; I reviewed the tapes for both Aircraft X and Aircraft Y's instructions/readbacks. There were no discrepancies with either--each pilot responded correctly and timely to the developmental's instructions but failed to comply.I am writing a report about the operation of this 'LAWA City Ramp' because it continues to cause unsafe proximity events. While I was previously under the impression that the majority of the errors were due to pilot expectation bias and over reliance on familiarity (the old Northroute was on K/L); I now believe that the instructions of the Ramp Tower personnel contributed to Aircraft X's deviation today. See below:When we told Aircraft X that they turned too soon; their response was 'we had further clearance to continue via K short of K2.' It is my belief that Aircraft X called the City Ramp on their second radio while taxiing westbound on B and the ramp personnel instructed them to continue via K short of K2. Aircraft X understood this as a complete change from the instructions we provided and began to turn on K early. If this is approximately what happened; then it needs to be remedied immediately. It's unsafe to have non-ATC personnel issuing instructions to aircraft that could be confused with new or amended instructions for how to taxi/proceed on the movement area. The ramp personnel need to clearly define to inbound aircraft that the previous clearance remains the same; but once on L short of K1; they may continue; hold; etc.Additionally; this is about the actions of pilots that turn early onto L/K when they correctly were issued and read back 'the Northroute.' I previously stated that 'I'd recommend additional signage; a change to the charts; or added emphasis in the text of the 'Northroute' that emboldens how N is now the Northroute; not K or L. Or all of the above;' and my sentiments still remain. I believe there was one small change to the Jeppesen map that tried to highlight the new ramp area but bolding the Northroute and re-emphasizing that N is the Northroute could also help prevent this occurrence.
LAX Ground Controller reported ongoing issues relating to poor signage at the airport.