ZOB CTLR EXPERIENCED OPERROR AT 16000 FT AS DEP ACFT OVERTOOK PRECEDING DEP ON SAME RTE.

Narrative

ACFT #1 AND #2 BOTH DEPS FROM SAME ARPT ON SAME RTE. ACFT #1 LEADING BY APPROX 7 MI. ACFT #1 CHKED ON FREQ AT 280 KTS OR LESS ASSIGNED SPD; ASKED ACFT #1 WHAT NORMAL SPD IN CLB WOULD BE. REPLY WAS 290 KTS. ACFT #1 ISSUED NORMAL SPD. ACFT #2 CHKED ON ASSIGNED 280 KTS. BOTH ACFT ISSUED CLB TO FL230. ACFT #1 ISSUED A XING RESTR TO CLR ABOVE XING TFC AND WAS ASKED IF THIS WOULD BE A PROB. REPLY WAS 'NO PROB.' ACFT #1 REDUCED SPD APPROX 50 KTS TO EXPEDITE CLB WITHOUT NOTIFICATION. ACFT #2 WAS TURNED 90 DEGS WHEN RADAR SHOWED SPD DIFFERENTIAL. CLOSEST PROX WAS 4.7 MI. PLT OF ACFT #1 LATER STATED (TELEPHONE); 'I THOUGHT I WAS BEHIND ACFT #2 BECAUSE OF APCH CTL'S ASSIGNMENT OF 280 KTS OR LESS. I DIDN'T NEED TO SLOW AND COULD HAVE FLOWN THE ACFT DIFFERENTLY.' PLT'S ASSUMPTION HAS RESULTED IN MY LOSS OF CERTIFICATION. CFR PART 91 NO LONGER CONTAINS ANY REQUIREMENT TO NOTIFY ATC OF SPD CHANGES. THIS MAKES LONGITUDINAL SEPARATION A GAMBLE UNLESS SPDS ARE ASSIGNED TO EVERY ACFT. A SIT THAT HAMPERS THE PLT AND CREATES EXCESSIVE WORKLOAD FOR THE CTLR.