Date: 202201
Local time of day: 0601-1200
Location: LAX.Airport, CA
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Tower LAX
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Human factors: Workload; Time Pressure; Other / Unknown; Confusion; Communication Breakdown; Situational Awareness
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Deviation / Discrepancy - Procedural Clearance; Ground Event / Encounter Weather / Turbulence; Ground Incursion Runway; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: Taxi
Result: Air Traffic Control Provided Assistance; Flight Crew Became Reoriented; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Human Factors; Environment - Non Weather Related
Primary problem: Ambiguous

Narrative: Upon check in with Approach; we were advised that we would fly the ILS 24R due of traffic. Loaded ILS 24R into the FMS; briefed the approach and discussed the taxi via standard taxi route back to the South complex. Upon landing; started the exit off of 24R at Taxiway AA and we were told to hold short of 24L; (visibility was 2 miles due to fog.)Quickly consulted the Airport Moving Map (AMM) chart to determine if this would lead to a taxi onto a parallel taxiway; like with the more familiar southern runways; or a direct crossing via an angle or a 90 degree turn. Upon looking up and trying to make sense of the visual; I saw the 24L hold short line but no signage. I was momentarily confused and thought the hold short line was the exiting hold short line for 24R. Upon realizing it was the hold short for 24L; I immediately stopped the aircraft; but the nose of the aircraft had crossed the hold short line by approximately 5 feet.I told the First Officer to radio Tower to tell them we stopped across the hold short line. They acknowledged our transmission; told us to hold our position; and then cleared us across the runway onto Taxiway AA to cross the field to the Southern complex. [Possible causes are] reduced visibility; lack of signage; [and] lack of recent experience with approaches to north runways at LAX. [Other possible causes are] unperceived bias and distraction during critical phase. [Possible solutions are to] stay heads up at critical points at airport; resist biases from previous experience at familiar airports; and to fully comprehend the anticipated taxi route you will receive. [Be aware of] expected vs assigned ATC clearance.


Second narrative: Once we checked in with approach we were given the ILS 24R. ILS 24R was loaded in the FMS and the new approach was briefed. Standard taxi routes were discussed in the brief and Standard taxi routes chart was reviewed. After landing we exited at AA and we were told to hold short of 24L. Captain called for flaps up as we exited and I began the after landing flow. While my head was down completing the after landing flow I felt the aircraft come to a sudden stop. I asked what was wrong and looked up. The Captain asked if we were past the hold short and quickly answered himself with yes we are past. I looked out my right window to see the hold short line for 24L out my right window and the nose of the aircraft was past the hold short line. As I brought my head up when the aircraft suddenly stopped I had a moment of confusion on our exact location. Captain instructed me to call the tower to tell them we were past the hold short line and I complied. Tower acknowledged and told us to hold our position and then cleared us across the runway and continue on Taxiway AA towards the southern complex.Cause - Lack of experience in the type aircraft which diminished my SA. Limited LAX experience especially on the north side. Distracted during a critical phase of flight with heads down completing the after landing flow. Suggestions - Stay heads up during critical phases of flight. Identify short distance between landing runway and hold short runway as a threat. Realizing the threat suggest that after landing flow be delayed until we are holding short of crossing runway.


Synopsis: Air Carrier Captain reported a runway incursion due to signage issues; poor visibility; late runway change from ATC; and lack of familiarity with a seldom used portion of LAX airport.