ACR CAPT WRITES DOWN CLRNC WITH XING RESTRICTION. TOTALLY FORGETS; MAKES RAPID DSCNT WHEN REMINDED BY ATC.

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DURING ROUTINE FLT ORD - RIC; ATC ISSUED XING RESTRICTION 40 W OF RIC AT 9000 FT. PERHAPS I WAS DISTRACTED; BUT I PROMPTLY FORGET ABOUT THE XING RESTRICTION; I EVEN WROTE IT DOWN! AT APPROX 42 W OF RIC AND DSNDING 290 KIAS AT APPROX 13 - 14;000 FT; ATC INQUIRED AS TO WHETHER OR NOT WE WOULD MAKE THE XING RESTRICTION. I IMMEDIATELY REMEMBERED; APOLOGIZED; AND ASKED FOR RELIEF. A QUICK CHK OF TCASII SHOWED NO TFC CONFLICT. I PUSHED THE NOSE DOWN TO BARBER POLE; APPROX 350 KIAS; AND LEVELED OFF 9250 FT TO BLEED OFF AIRSPD; NOW WELL INSIDE 40 MI RESTRICTION (APPROX 35 DEG.) MY REASONING WAS THAT IF THERE WAS NON- TRANSPONDER EQUIPPED IFR TFC; IT WOULD BE BETTER TO BE AT ALT AND 100 KIAS TOO FAST AT 9000 FT; THAN BE AT 250 KIAS AND COLLIDE WITH SOMEBODY AT 10000. ABOUT THE TIME WE LEVELED OFF; ATC PROVIDED RELIEF FROM THE XING RESTRICTION AND HANDED US OFF TO APCH CTL. THIS WAS NOBODY'S FAULT BUT MINE. (FO WAS BUSY WITH NEW ATIS; ETC. AT MY REQUEST.' IT WAS THE END OF A LONG DAY: (LATE PM.) CURE - ETERNAL VIGILANCE?