EMB 145 FLT CREW INADVERTENTLY CROSSED A RWY WHILE TAXIING FOR TKOF; CITING CONFUSION WITH CHART DEPICTION.

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DEPARTING FROM GATE WE WERE GIVEN THE TAXI CLRNC W BOUND ON TXWY H; THEN B; J HOLD SHORT RWY 9R. WE REVIEWED THE ARPT DIAGRAM CHART; AND STARTED THE TAXI OUT W BOUND ON TXWY H. THE CHART APPEARS TO INDICATE THAT TXWY H TURNS INTO TXWY B JUST PAST THE INTXN OF TXWY H AND C; AND IT APPEARS THAT TXWY B PROCEEDS ACROSS RWY 22R/4L. WE FOLLOWED WHAT WE THOUGHT FROM THE CHART WAS TXWY B ACROSS RWY 22R/4L; AS NO HOLD SHORT INSTRUCTION WAS GIVEN FOR THAT RWY; AND PRIOR TO CROSSING VERIFIED LNDG TFC WAS EXITING THE RWY. AFTER CROSSING ATC INSTRUCTED TO HOLD SHORT OF TXWY J AND CONTACT THEM ON A SEPARATE FREQUENCY. THIS IS WHEN WE LEARNED OF OUR MISTAKE AND WHAT THE ACTUAL TAXI ROUTE WAS SUPPOSED TO BE. THEY ADVISED AT THAT TIME THAT NO TFC SEPARATION WAS COMPROMISED; NO GARS ISSUED; AND NO IMMEDIATE SAFETY THREAT. UPON FURTHER REVIEW OF THE ARPT DIAGRAM THE TXWY B CURVES TO THE L BUT THE LOCATION OF THE TXWY DESIGNATION FOR TXWY B ON THE DIAGRAM IS MISLEADING AND IS WHY WE FELT WE WERE CORRECTLY FOLLOWING OUR TAXI CLRNC. THIS EVENT OCCURRED BECAUSE OF A CONFUSING ARPT DIAGRAM CHART THAT INADEQUATELY SHOWS THE PROPER TXWY DESIGNATION FOR THE CLRNC WE WERE ISSUED. WE WERE ALSO SEVERELY DELAYED DUE TO WEATHER AND THE FACT THAT OUR ONLY FMS WAS DEFERRED. WE DIDN'T KNOW WE HAD DEVIATED FROM THE CLRNC UNTIL WE HAD CROSSED THE RWY. BETTER DESIGNATION AND CLARIFICATION OF THE TXWYS IN THAT AREA OF THE H INTXN AT B AND OF RWY 22R/4L OF THE CHICAGO ORD ARPT DIAGRAM.