OPERROR LTSS WHEN APPROPRIATE SEPARATION IS LOST BTWN A DEPARTING DC9 AND A PRECEDING C208 DEP. RPTR STATED BOTH ACFT WERE IMC WHEN THE DC9 PASSED TO L OF THE C208.

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WE WERE GIVEN A TKOF CLRNC INAPPROPRIATELY CLOSE BEHIND A CESSNA CARAVAN (MUCH SLOWER ACFT). WE WERE ON GND CTL FREQ UNTIL READY FOR TKOF SO WE DID NOT HEAR THE DEP HDG FOR THE CESSNA. I ASSUMED IT TO BE A GREATLY DIVERGENT HDG. WE WERE GIVEN A TKOF CLRNC TO FLY RWY HDG. THERE WAS ANOTHER ACFT ON FINAL APCH SO WE COULD NOT DELAY OUR TKOF. I SAW THE CARAVAN BEGIN A SLOW TURN TO THE R SO WE BEGAN OUR TKOF. THE CARAVAN HAD SELECTED THE WRONG CODE AND THE TWR ASKED IF THEY WERE IN THEIR TURN AND TO SQUAWK THE CORRECT CODE. I TOLD THE FO; PF; TO TURN SLIGHTLY L TO INCREASE OUR MISS DISTANCE. I WATCHED THE CARAVAN ON TCASII TO INSURE LATERAL CLRNC. WE PASSED THEM ON THEIR L SIDE IN OUR CLB. WE PASSED CO-ALT AS WE OUT- CLBED THEM AT WHAT I WOULD ESTIMATE AT LESS THAN A MI. WE WERE BOTH IMC. AS A FORMER MIL INTERCEPTOR PLT; I'VE DONE THIS A LOT BEFORE; BUT THIS IS INAPPROPRIATE SEPARATION FOR ACRS. PIT ATC SEEMS TO PLAY FAST AND LOOSE WITH THE RULES AND I FEEL IT PUTS PEOPLE AT RISK. THE PREVIOUS EVENING ARRIVING AT PIT; THE CTLR TOLD US TO MAKE A VISUAL APCH WHEN WE DIDN'T SEE THE ARPT. THE PLT IS THE ONE WHO INITIATES THE VISUAL APCH. PIT ATC IS BAD NEWS!