Date: 201911
Local time of day: 1801-2400
Location: LGA.Airport, NY
Flight conditions: IMC
Weather elements / visibility: 2
Light: Night
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ramp LGA
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Communication Breakdown
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Incursion Taxiway
Detector: Person Air Traffic Control
When detected: Taxi
Result: Air Traffic Control Provided Assistance; Flight Crew Became Reoriented
Contributing factors: Human Factors; Environment - Non Weather Related; Weather
Primary problem: Human Factors

Narrative: We landed uneventfully; but late; at LGA at night; with rain and two miles visibility. Once the Captain started taxiing; I confirmed that the gate was open and then told Ground. They asked if the alley was open; because 'it had been an issue lately;' so I asked Ramp. Ramp said that (other carrier) was in the alleyway and we could taxi in when (other carrier) taxied out. We taxied on Bravo; held short of Juliet (per Ground's instructions) and waited. It was night; it was raining but we could see a light blue (other carrier) sitting at the top of the alley after having just been pushed back. It is well documented that LGA does not have signs; only pavement markings to delineate Taxilane 8 versus 9.We had discussed in the preflight briefing prior to landing; the location of Taxilane 9; since I was on a flight months ago; where we went past that. We knew it was just past Taxiway Lima. (Other carrier) started to taxi out; we informed Ground; and he cleared us onto Alpha to the Ramp. Multiple aircraft behind us were also cleared to follow us into the ramp. I made a radio call to Ramp telling him we were inbound and he told us that (other carrier) was still in the alley. As we got closer; we saw a little (other carrier) roughly at position 9D. He had a dark paint scheme; was at the base of the alley and we could only see him once we had taxied closer. There were two (other carrier) aircraft in the alley; we were simply told to 'taxi in after (other carrier) taxied out.'At that point we stopped; asked Ground what he wanted us to do; and he informed us that we 'had to get off Alpha because we were blocking his aircraft flow to the runway.' The Captain exited on Taxilane 8; the (other carrier) pulled up towards 9A and he transitioned behind the (other carrier) to Taxilane 9. We taxied uneventfully to Gate. I was merely trying to tell the Ramp Controller that his instructions were misinterpreted because we were not told the type of aircraft and that there were actually two (other carrier) in the alley. I couldn't get a word in because the Ramp Controller merely wanted to argue about how he was the clearance authority for the ramp; etc. He was upset that we didn't see the second (other carrier) aircraft and that the Captain used common sense to transition behind (other carrier) to Taxilane 9; which was where we were expected to enter anyway.Inform the Ramp Controllers that at night; in adverse weather and reduced visibility; with taxilane markings on the concrete (not signs) that are not visible to Aircrew; that it is imperative to be specific with his triggers. Aircrew are expected to talk to two Controlling Agencies and work out these problems; but the two Controlling Agencies never talk to one another; so Pilots are the go-betweens. The Ramp Controller was only concerned with his designated authority for taxi instructions in the ramp/alleyway; rather than realizing why we were not able to read his mind and had to get off of Alpha because we were already committed; once on Taxiway A. I'm guessing; the Ramp Controllers probably could use additional training and/or procedures; since Ground already informed us that the ramp 'had been an issue lately'.




Synopsis: Air carrier First Officer reported communication issues with LGA ATC regarding taxi instructions.