B737-300 CREW HAD CONFUSING TAXI CLRNC ISSUED OVER AN ACARS TELEMETRY TEST AT IAD.

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INCIDENT CONCERNS COMPANY TEST PROC AT IAD. RECEIVED A RESPONSE VIA ACARS FROM OUR TR TO 'MONITOR GND 132.45; ATIS CURRENT; EXPECT RWY 19R; EXPECTED TAXI CLRNC TURN R ON TXWY Z.' WE TURNED R ONTO TXWY Z WITHOUT VERBAL CLRNC FROM GND CTLR. CONTRIBUTING FACTORS: 1) LAST TIME INTO IAD WAS MONTHS AGO AND COMPANY TEST PROC WAS NOT IN EFFECT. 2) ON INBOUND PREVIOUS DAY WE AUTOMATICALLY RECEIVED GATE INFO ON ACARS. 3) ON OUTBOUND THIS LEG; THE RESPONSE FROM OUR PR STATED 'PUSH APPROVED.' THESE 3 EVENTS LED US TO ASSUME COMPANY TEST PROC WAS UP AND OPERATIONAL. ADDITIONALLY; SUN ANGLE MADE READING THE ACARS DIFFICULT; AND WE SIMPLY MISSED THE 'EXPECTED TAXI CLRNC' LINE. COMMENTS: TEST OF COMPANY TEST PROC DOESN'T SEEM TO INCLUDE GND CTLRS. THEY MADE A COMMENT THEY DON'T HAVE ANY IDEA WHAT THE INFO PRINTED TO ACARS CONTAINS. ALSO COMPANY TEST PROC SEEMS TO BE DESIGNED TO INCREASE ON-TIME PERFORMANCE DUE TO FREQ CONGESTION; YET IT CAUSES A GREAT DEAL OF 'HEADS DOWN' TIME AND CAUSES A REDUCTION OF SITUATIONAL AWARENESS -- YOU HAVE NO IDEA WHO IS PUSHING OR TAXIING AROUND YOU. WHY NOT HAVE JUST IAD DOMICILED PLTS PERFORM THE TEST VERSUS ALL PLTS. I'M SURPRISED WE DON'T HAVE MORE INCIDENT OF TAXI PROBS AT IAD AS A RESULT OF THE DDTC TEST.