B737 flight crew at mdw experienced confusing taxi instructions resulting in near runway incursion.

Attributes
ACN	583186
Time
Date	200305
Day	Sun
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : mdw.airport
State Reference	IL
Altitude	agl single value : 0
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	tower : mdw.tower
Operator	common carrier : air carrier
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Flight Phase	ground : holding ground : parked
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tower : mdw.tower
Make Model Name	King Air 100 A/B
Flight Phase	climbout : takeoff climbout : initial
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 240 flight time total : 6400 flight time type : 1500
ASRS Report	583186
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	conflict : ground less severe incursion : runway non adherence : clearance
Independent Detector	other controllera
Resolutory Action	controller : issued alert controller : issued new clearance
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 1000 vertical : 100
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Operating flight from oca-MDA. After clearing runway 4R, received notice that our gate was occupied and received taxi instructions back to runway 22L holding pad where we held on taxiway north. Shortly thereafter, we received notice of a gate change and received taxi clearance from ground controller to taxi left on taxiway north to hold short of runway 4R. As our aircraft approached runway 4L, we began to initiate a turn onto taxiway P to hold short of runway 4R as is often the case for aircraft taxiing from the holding pad to terminal when runway 4R is the active runway. The ground controller stated 'air carrier X, stop,' as we initiated a turn onto taxiway P, and off of runway 4L. The controller then stated 'air carrier X, hold short of runway 4R on taxiway P, and explained the taxi clearance was to taxi on taxiway north to hold short of runway 4R. Confusion of the taxi clearance as we were on taxiway north led to the assumption that we were to taxi onto taxiway P to hold short of runway 4R which is the general taxi clearance for crossing runway 4R. I believe clarification of our taxi clearance would have prevented the misunderstanding.

Original NASA ASRS Text

Title: B737 FLT CREW AT MDW EXPERIENCED CONFUSING TAXI INSTRUCTIONS RESULTING IN NEAR RWY INCURSION.

Narrative: OPERATING FLT FROM OCA-MDA. AFTER CLRING RWY 4R, RECEIVED NOTICE THAT OUR GATE WAS OCCUPIED AND RECEIVED TAXI INSTRUCTIONS BACK TO RWY 22L HOLDING PAD WHERE WE HELD ON TXWY N. SHORTLY THEREAFTER, WE RECEIVED NOTICE OF A GATE CHANGE AND RECEIVED TAXI CLRNC FROM GND CTLR TO TAXI L ON TXWY N TO HOLD SHORT OF RWY 4R. AS OUR ACFT APCHED RWY 4L, WE BEGAN TO INITIATE A TURN ONTO TXWY P TO HOLD SHORT OF RWY 4R AS IS OFTEN THE CASE FOR ACFT TAXIING FROM THE HOLDING PAD TO TERMINAL WHEN RWY 4R IS THE ACTIVE RWY. THE GND CTLR STATED 'ACR X, STOP,' AS WE INITIATED A TURN ONTO TXWY P, AND OFF OF RWY 4L. THE CTLR THEN STATED 'ACR X, HOLD SHORT OF RWY 4R ON TXWY P, AND EXPLAINED THE TAXI CLRNC WAS TO TAXI ON TXWY N TO HOLD SHORT OF RWY 4R. CONFUSION OF THE TAXI CLRNC AS WE WERE ON TXWY N LED TO THE ASSUMPTION THAT WE WERE TO TAXI ONTO TXWY P TO HOLD SHORT OF RWY 4R WHICH IS THE GENERAL TAXI CLRNC FOR XING RWY 4R. I BELIEVE CLARIFICATION OF OUR TAXI CLRNC WOULD HAVE PREVENTED THE MISUNDERSTANDING.

Data retrieved from NASA's ASRS site as of July 2007 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.