ACR ON VISUAL APCH AT NIGHT MUST MAKE GAR DUE ACFT ON RWY IN TKOF POS.

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AFTER PASSING DIALS FLYING 085 DEGS ON THE EXPRESSWAY VISUAL 31 THE TWR (118.7) CLRED US TO LAND ON 31 AND APPROVED SHORT APCH. ANOTHER ACFT AHEAD OF US WAS ALSO USING SAME APCH BUT LANDED 5 PLUS MINS AHEAD OF US. WE TURNED FINAL ABOUT 3 1/2 MI OUT WITH FINAL DSCNT CHK COMPLETE; ARPT; RWY LIGHTS AND VASI IN SIGHT. AT THE 500 FT FLAP 30 CALL; I NOTICED 2 WHITE LIGHTS THAT SEEMED OUT OF PLACE. WE THEN ASKED TWR IF THERE WAS AN ACFT ON RWY! IT BECAME MORE OBVIOUS BOTH VISUALLY AND WHEN ACR ANSWERED THAT THEY WERE; IN FACT; ON END OF RWY SO GAR WAS INITIATED AT APPROX 350 FT AGL. WE WERE NEVER ADVISED OF ACFT IN POS; PLUS ACFT APPEARED TO HAVE NO LNDG LIGHTS ON AND NO STROBE LIGHTS! IDENTITY WOULD HAVE BEEN MUCH SOONER WITH LIGHTS ON. AFTER ADVISING TWR OF GAR WE WERE GIVEN RWY HDG; 2000 FT; AND LATER TUNED DOWNWIND FOR QUICK VISUAL TO 31. THE TWRS COMMENT TO ACR WAS THAT HE TRIED CONTACTING THEM BUT TRANSMISSIONS WERE BLOCKED. WE DIDN'T HEAR ANY ATTEMPTS; IN EITHER CASE; WE WERE NOT ADVISED; CLRED TO MAKE SHORT APCH AND CLRED TO LAND. WAS ACR CLRED INTO POS OR TO HOLD SHORT? PAX AND CREW WERE TOLD WHY WE HAD TO GAR AND THEY WATCHED ACR TKOF AS WE TURNED DOWNWIND TO COMPLETE A NORMAL LNDG. AFTER WE SHUTTLED BY VAN TO HOTEL IN EWR; I CONTACTED DISPATCHER AND FLT DUTY MGR. THEY BEGAN THEIR PRELIMINARY RPTS WHILE I COMPLETED THIS CAPT'S RPT. IT'S NOW VERY CLR TO ME HOW EASILY A CREW MIGHT LAND ON TOP ANOTHER ACFT WHEN THE HIGH VISIBILITY STROBES AND LNDG LIGHTS ARE NOT IN USE. LACK OF COM COULD HAVE LED TO GRIM RESULTS! WE MUST ALL STRIVE TO BREAK THE 'ERROR CHAIN!'