Narrative:

After landing on runway 31C at mdw; ground control gave us the following clearance to taxi to the gate. 'Back-taxi runway 31R; cross runway 22R and runway 22L; papa; tango to the gate.' that's the clearance the first officer read back and that we both understood. After the clearance I referenced my 10-9 page for mdw to verify the routing. I believe the 10-9 page is poorly marked. On the ramp you have the confluence of taxiways Y; P; and T. Taxiway P is marked just above the area where P and Y intersect; but the P is actually placed closer to the continuation of taxiway Y just prior to crossing 31R; and there is no clear designation of the continuation of Y or P on the ramp side. Only in between 31R and 31C is the continuation for both taxiways marked. So while taxiing in; I quickly glanced at the 10-9 and thought the first taxiway after crossing 22L was P and turned instead onto Y. The ground controller then mentioned I turned onto Y instead of P as instructed. We acknowledged the radio call. Also contributing to the confusion I believe was [that] we landed and it was still dark outside; so even with taxiway lighting it's not as easy to pick out a routing as it would be in the daytime at an airport such as mdw with multiple crossing taxiways. Also; since the turnoff for Y and P are just past the crossing of 22L; the first officer and I were busy clearing while crossing two active runways while taxiing on a third active runway and so our attention was distracted from picking out the correct taxiway as we were prioritizing clearing all active runways.I think a few things could help. First; I could have tried to take a few more seconds looking at the 10-9 page to ensure I knew the controller's instructions. Having taxied around mdw a lot; I was admittedly a bit complacent in glancing at the 10-9 and I've never realized how poorly that area is actually marked. Also; I think if the area currently marked by the HS4 spot had the letter Y placed inside the HS4 circle; and the letter P placed in a similar location on the continuation of P before 31R would greatly help. Lastly; mdw ground controllers seem to be utilizing 31R back-taxi a lot lately whereas we were never given that option in the past. Unless sections of north and P between the 22s are closed and I missed it; I think it would help for ATC to clarify with the company if they plan on utilizing 31R back-taxi more now and what we might expect as 'standard' taxi clearances if that's the case. That would help to frame our mental model and prevent expectation bias.

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Original NASA ASRS Text

Title: An air carrier Captain became confused about Taxiways P; Y; and T after landing in darkness and turned on an incorrect taxiway. The taxiway confluence and markings are confusing.

Narrative: After landing on Runway 31C at MDW; Ground Control gave us the following clearance to taxi to the Gate. 'Back-taxi Runway 31R; cross Runway 22R and Runway 22L; Papa; Tango to the gate.' That's the clearance the FO read back and that we both understood. After the clearance I referenced my 10-9 page for MDW to verify the routing. I believe the 10-9 page is poorly marked. On the ramp you have the confluence of Taxiways Y; P; and T. Taxiway P is marked just above the area where P and Y intersect; but the P is actually placed closer to the continuation of Taxiway Y just prior to crossing 31R; and there is no clear designation of the continuation of Y or P on the ramp side. Only in between 31R and 31C is the continuation for both taxiways marked. So while taxiing in; I quickly glanced at the 10-9 and thought the first taxiway after crossing 22L was P and turned instead onto Y. The Ground Controller then mentioned I turned onto Y instead of P as instructed. We acknowledged the radio call. Also contributing to the confusion I believe was [that] we landed and it was still dark outside; so even with taxiway lighting it's not as easy to pick out a routing as it would be in the daytime at an airport such as MDW with multiple crossing taxiways. Also; since the turnoff for Y and P are just past the crossing of 22L; the FO and I were busy clearing while crossing two active runways while taxiing on a third active runway and so our attention was distracted from picking out the correct taxiway as we were prioritizing clearing all active runways.I think a few things could help. First; I could have tried to take a few more seconds looking at the 10-9 page to ensure I knew the Controller's instructions. Having taxied around MDW a lot; I was admittedly a bit complacent in glancing at the 10-9 and I've never realized how poorly that area is actually marked. Also; I think if the area currently marked by the HS4 spot had the letter Y placed inside the HS4 circle; and the letter P placed in a similar location on the continuation of P before 31R would greatly help. Lastly; MDW Ground Controllers seem to be utilizing 31R back-taxi a lot lately whereas we were never given that option in the past. Unless sections of N and P between the 22s are closed and I missed it; I think it would help for ATC to clarify with the Company if they plan on utilizing 31R back-taxi more now and what we might expect as 'standard' taxi clearances if that's the case. That would help to frame our mental model and prevent expectation bias.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.