A TAXIING B737-300 OFF RWY 22R ONTO TXWY C TURNS ONTO TXWY A INSTEAD OF TXWY B. A GND CONFLICT ENSUES WITH A TAXIING B747-400.

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LANDED RWY 22R AT ORD. TOLD TO EXIT TXWY C AND CROSS RWY 27R AND TO CALL GND. GND SAID 'TURN ON TXWY B.' WE WERE NOSE-TO-NOSE WITH A B747-400 AT THE JOINT INTXN OF TXWY A; B; H; AND C. WHEN I LOOKED AT THE SIGNAGE; A YELLOW BACKGND SIGN POINTED TOWARD WHAT I THOUGHT WAS TXWY B. HOWEVER; I STOPPED BECAUSE AN AIRPLANE WAS COMING DOWN THE TXWY I BELIEVED TO BE TXWY B. MY FO AGAIN ASKED IF WE WERE CLRED ONTO TXWY B -- AGAIN; YES. ANOTHER ACFT APCHED ON TXWY B AT A HIGH RATE OF SPD. AT THIS TIME; I MOVED QUICKLY (A 180 DEG TURN) TO KEEP FROM GETTING HIT AND MY FO GOT INTO THE GND TAXI CHART AND REMINDED ME 'TXWY A' IS 'INNER' AND 'TXWY B' IS 'OUTER.' I QUICKLY TURNED ON TXWY B. SINCE THAT TIME; I HAVE BEEN ON THE JUMP SEAT 2 MORE TIMES AND THE SCENARIO REPEATED ITSELF. TODAY; IN THE DAYLIGHT; I FINALLY UNDERSTOOD WHY: WHEN YOU TURN OFF TXWY C; YOU CROSS TXWY H PRIOR TO JOINING TXWY B. THE EXISTING TXWY SIGNAGE IS ACTUALLY FOR TXWY H; EVEN THOUGH IT ACTUALLY APPEARS TO BE FOR TXWY B WITH AN ARROW POINTING TOWARD TXWY A AND MAKES IT LOOK LIKE THE TXWY B SIGN POINTS TOWARD TXWY A. FROM THE L SEAT; YOU DO NOT EVEN NOTICE TXWY H. THE ANGULAR DIFFERENCE BTWN TXWY B AND TXWY H AT THIS POINT IS SO SUBTLE IT MAKES TXWY A APPEAR TO BE TXWY B. SINCE THE TAXI DISTANCE IS SO SHORT FROM XING RWY 27R; I BELIEVE THAT BOTH SIGNAGE AND ATC PROCS SHOULD BE MODIFIED TO PREVENT THE TYPES OF HUMAN FACTORS CONFUSION WHICH NEARLY CAUSED ANOTHER AIRPLANE TO HIT US. FIRST; I BELIEVE THE CURRENT SIGN NEEDS TO BE REMOVED AND MOVED A FEW FT TO SHOW A BLACK BACKGND 'TXWY B' ON THE L SIDE OF TXWY B WITH AN ARROW POINTING TOWARD TXWY A. A SECOND SIGN WITH A BLACK BACKGND SHOULD BE ADDED TO SHOW TXWY H A FEW FT FURTHER TO THE NE. PLTS EXITING RWY 22R OR RWY 27R DO NOT NEED TO SEE THE TXWY H SINCE THEY DO NOT USE TXWY H. INSTEAD; THEY NEED TO FIND TXWY B AT THIS POINT. SECOND; ATC NEEDS TO SPECIFY WHICH DIRECTION TO TURN ON TXWY B IF THEY CARE WHETHER YOU TRAVEL CLOCKWISE OR COUNTERCLOCKWISE ON TXWY B. THEY SHOULD NOT RELY ON ALL PLTS HAVING SUFFICIENT 'LCL KNOWLEDGE' TO KNOW THE TXWY B USUALLY MOVES COUNTERCLOCKWISE AND TXWY A MOVES CLOCKWISE. THIS VERY COMPLEX INTXN; POOR/CONFUSING SIGNAGE AND A VERY HIGH WORKLOAD AS YOU CLR ONE RWY; CROSS ANOTHER AND GO TO GND CTL IN A VERY SHORT TIME PERIOD AND TAXI RTE BECOMES A VERY STRONG CANDIDATE FOR THE SITE OF A VERY SPECTACULAR ACCIDENT. YOU NEED TO LOOK AT THE CHART 20-9 TO UNDERSTAND THIS AND EVEN IT IS LESS THAN ACCURATE. THE CHART SHOWS AFTER RWY 27R THAT TXWY C LEADS ONTO TXWY H THEN TXWY B. THIS IS HOW THE SIGNAGE IS. HOWEVER; THE CTLRS OMIT ANY MENTION OF TXWY H; WHICH THE SIGNAGE ACTUALLY SHOWS AS YOU TURN ONTO TXWY B. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR IS A UNION SAFETY MEMBER THAT DEALS WITH CHARTING. HE FEELS THAT THIS IS AN IMPORTANT ISSUE SINCE HE CAME 'NOSE-TO-NOSE' WITH A FAST MOVING B747 ON TXWY A; THE INNER. THE CAPT FEELS THAT IF THE TWR OR GND CTLR WOULD SIMPLY SAY 'TXWY B; THE OUTER' INSTEAD OF JUST 'TXWY B' THAT THE CREWS WOULD HAVE A BETTER UNDERSTANDING OF WHICH TXWY WAS BEING REFED. THE LCL CREWS KNOW THAT THE INNER IS CLOCKWISE AND THE OUTER IS COUNTERCLOCKWISE; BUT THE 'OUT OF TOWNERS' DON'T REALIZE THIS FACT. THE 2 OTHER FLTS THAT HE HAD JUMP SEATED WITH HAD FLCS FALL INTO THE SAME TRAP; ENTERING THE INNER AGAINST TFC.