Date: 202104
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Small Aircraft; Low Wing; 1 Eng; Retractable Gear
Operator: Personal
Operating under: Part 91
Flight plan: VFR
Mission: Personal
Flight phase: Takeoff / Launch
Airspace: Class D ZZZ
ATC / advisory: Tower ZZZ
Second aircraft: Small Aircraft
Reporter organization: Personal
Reporter function: Single Pilot; Pilot Flying
Reporter qualification: Flight Crew Private
Human factors: Training / Qualification; Confusion; Communication Breakdown; Situational Awareness
Second reporter function: Local
Anomaly: Conflict Ground Conflict; Critical; Deviation / Discrepancy - Procedural Clearance; Ground Incursion Taxiway
Detector: Automation Air Traffic Control; Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert
Contributing factors: Environment - Non Weather Related; Human Factors
Primary problem: Human Factors

Narrative: I taxied from the southeast ramp intending to use Runway XXR for takeoff. When exiting the ramp Taxiway Alpha has an unmarked entrance at the very southeast end of the airport. While holding at the entrance line to Alpha ground cleared me to the Bravo run-up area just ahead of me. I did so crossing two separate dash lines on the pavement and then turned 180 deg facing back at the ramp. I saw no sign for the Bravo Taxiway nor for Runway XXR. The Tower cleared me for takeoff; but did not say to use Bravo to get to the runway which was behind me. Once cleared for takeoff I crossed both sets of dashed lines thinking I was on Runway XXR but later realized I was aligned with a taxiway.The contributing factors were entering Taxiway A at an unmarked intersection and then crossing two sets of dashed lines to the run-up area that had no marking signs. Once at the run-up area I did not see any signs for Taxiway Bravo or [Runway] XXR. Perhaps another contributing factor was not flying for seven months prior to this flight because of COVID.In retrospect during flight planning; I should have gotten an enlarged airport diagram and studied it thoroughly; anticipating my route to the assigned runway and noting any potential issues in advance. I would then zoom in on satellite maps to clarify what it actually looked like on the ground. If that didn't clear it up I would call Ground Control and discuss it with them before arrival. If I'm ever uncertain when actually taxiing I can always ask for progressive taxi instructions from Ground Control.


Second narrative: Aircraft X was issued a takeoff clearance for Runway XXR and departed on Taxiway 'A' which runs parallel to the runway. The Local Controller was issuing traffic to other aircraft and did not see the Aircraft X rolling on Taxiway 'A'. By the time we caught it I told the local controller not to cancel the takeoff clearance as it was heading directly for Aircraft Y that was taxiing opposite direction on Alpha and the departing aircraft would not have had the space to stop before a collision would've ensued. The departing aircraft passed what I estimate to be 70-90 feet above Aircraft Y on the taxiway.Recommendation - Continuation by the FAA to inform and educate pilots on the hazards associated with wrong surface departures.


Synopsis: GA pilot and ATC Tower personnel reported the pilot departed from a taxiway resulting in a conflict. Pilot cited lack of flying as a contributing factor.