Date: 202110
Local time of day: 1801-2400
Location: SBN.Airport, IN
Flight conditions: IMC
Weather elements / visibility: Wind
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Taxi
ATC / advisory: Tower SBN
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Situational Awareness; Distraction; Confusion
Second reporter function: First Officer
Anomaly: Conflict Ground Conflict; Less Severe; Deviation / Discrepancy - Procedural Clearance; Ground Incursion Taxiway; Ground Incursion Runway
Detector: Person Flight Crew
When detected: Taxi
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Became Reoriented
Contributing factors: Chart Or Publication; Procedure; Human Factors; Environment - Non Weather Related; Airport
Primary problem: Chart Or Publication

Narrative: As Captain of Aircraft X; inadvertently taxied onto an unmarked; newly constructed taxiway apron at night at South Bend (SBN).  Taxi plan from the company ramp to runway 36 via taxiway B was thoroughly briefed. With an aircraft on 4 mile final for runway 36; ground requested that we expedite taxi across runway 18/36 at B (from west to east) with follow on instructions to taxi B-N-hold short runway 36 at N3. There is a lot of construction on the airfield but no NOTAM regarding construction of a new taxiway just north of the current taxiway B between runway 36 and taxiway N. That area is not lit. Crossing runway 18/36 on the current taxiway B from west to east requires a brief dogleg south on runway 18/36 that is not depicted on the Jepps airport diagram. The new taxiway apron under construction aligns more closely with the current airport diagram.  It was also a very dark night.  Poor construction lighting on the apron barriers; inaccurate taxiway diagrams; darkness; faded taxiway B center lines on the runway; and failure of the crew to stop earlier on the runway due to an 'expedite' crossing clearance for an aircraft on final were the primary factors that contributed to us taxiing straight across Runway 18/36 and partially onto a newly constructed; closed taxiway before poorly lit portable barriers became visible.  Once we realized our mistake there was not enough room before the portable barriers to turn around.  Ground waved off the aircraft on approach because we were not sure if we were fully clear of Runway 36. The Company ramp said they were unable to tow us from that area so airfield operations confirmed that the apron could hold the aircraft weight; moved the portable barriers and allowed us to pull forward and conduct a 180 turn back onto runway 18/36.  The remainder of the taxi and flight was uneventful.Inaccurate airport taxi diagram doesn't show dogleg on runway when crossing runway 18/36 on taxiway B; low light night ops; poorly lit barriers in apron under construction; no mention of apron under construction in NOTAMs; pilot error due to hesitancy to stop on the runway to discuss faded taxiway B markings on runway due to aircraft on 4 mile final and ground controller request to expedite runway crossing. More accurate airport diagram that shows that taxiway B is staggered on each side of runway 18/36; requiring a brief taxi along runway to cross between west and east on taxiway B.  Better lighting on barriers in apron under construction between taxiway N and runway 18/36 north of taxiway B.  Include company note about staggered taxiway B.


Second narrative: On the evening of Date I was the First Officer for Aircraft X; a flight from SBN to ZZZ.  I don't recall the exact reported weather; but it was a low overcast night. There is a lot of construction taking place at SBN so the Captain and I first briefed the taxi plan of how we would get from the Company ramp to runway 36 while in the Company Ops facility at SBN. Reviewing the airport diagram; our plan was to exit the east taxiway departing the Company ramp onto taxiway B.  Once on B; we would have to taxi 'straight' across runway 18/36 onto B; turn south on N which would take us to N3 for a full length departure from runway 36.  During our cockpit departure brief; we once again briefed and reviewed our taxi plan as mentioned above.During our taxi; we exited the Company ramp onto taxiway B.  As we approached runway 36; tower cleared us to cross runway 36 at B and expedite our taxi for an aircraft on a 4 mile. The Captain and I gained visual of the traffic on final; referenced our chart and proceeded to cross runway 36.  Crossing Runway 36 on what we thought was B; we inadvertently taxied onto a new taxi apron under construction.  I informed tower we could not verify if our tail cleared the runway; so Tower instructed the aircraft of final to go-around.  The Captain and I received verification the new taxiway was greater than 120 feet; it was reported to be 150 feet; and we verified the area behind construction was usable. Ops confirmed the area was usable and received permission to move the barriers; and then show us the exact location where the hazard begins. Once the barriers were moved; we had appropriate space to execute a 180 degree turn.  We executed our 180 degree turn and taxied onto 36 where we turned south on 36 to join taxiway B and continue with our flight.  After the incident; the Captain and I reviewed the SBN taxi diagram.  The diagram shows crossing 36 on B is 'straight' across with no turn onto 36 to join B.  In short; the area where B joins 36 from the west; is actually north of where taxiway B joins 36 to the east.  We taxied straight across 36 and ended up in the new construction area.Incorrect airport diagram due to recent construction.  The current airport diagram shows taxiway B is straight across when crossing runway 18/36.   In reality; taxiway B on the east side of 18/36 is approximately 100 yards south of where taxiway B intersects the west side of 18/36.  A turn south to back taxi onto runway 36 is required when crossing B from west to east.


Synopsis: A flight crew taxiing for departure from SBN reported they taxied onto a closed taxiway under construction and possibly committed a runway incursion due to an inaccurate airport diagram and poorly lit barriers.