Small Aircraft; High Wing; 1 Eng; Fixed Gear
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 1.5
Communication Breakdown; Confusion; Situational Awareness
ATC Issue All Types; Conflict Ground Conflict; Less Severe; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Incursion Runway
Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Air Traffic Control Separated Traffic; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Became Reoriented
Airport; Human Factors
It was a typical busy day with many requests both inbound and outbound. Aircraft X called Ground Control on Taxiway Lima between the parallel runways requesting taxi to the northwest ramp. I issued 'taxi via Lima; Kilo; cross Runway 21 and hold short Runway 26 right at Kilo.' As the pilot read back the taxi route he appeared to hesitate and start a slight right turn onto Runway 21. I asked the pilot if he was familiar with taxiing between the parallel runways to which he replied 'no.' I then issued plain language instructions 'continue straight ahead and taxi kilo is the last right turn. As you make the turn the hold bars come up really quick so as you turn; slow to a stop.  The pilot acknowledged my instructions. As the pilot turned on Taxiway Kilo he passed the hold short bars. I immediately reached out to Aircraft X and told him to stop. At that time another aircraft was calling Ground Control with a request. Aircraft X stopped prior to the runway edge line. I then made Local Control - North aware and advised the Controller to send around the traffic that was on about a 1-1/2 mile final. I had issued the hold short instruction but in his confused taxiing I missed the hold short readback as I was attempting to stop the aircraft from turning on to Runway 21. The airport recently painted a yellow taxi line that leads off of Taxiway Lima and onto to Runway 21. I've seen several pilots get confused while taxiing and follow that yellow line inadvertently. The airport also painted some enhanced taxi lines and runway markings on the ground. I believe the yellow line leading off Taxiway Lima is and will continue to confuse pilots. I think additional signage in the midfield clearly showing taxi routes would help the pilots who continue to 'get lost' while taxiing in these hotspots.
CNO Tower Controller reported a pilot was confused by their taxi instructions and taxied past the hold short lines before the Controller could stop them causing an aircraft on short final to go-around. The reporter states new taxiway markings are routinely confusing the pilots.