ACFT TAXIED INTO A DRAINAGE DITCH AT NIGHT.

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ON LNDG ROLLOUT (RWY 7) AT VGT; I EXITED RWY AT TXWY C AT A SLOW SPD. AT THAT TIME I NOTICED MY LNDG LIGHTS WERE INOP. CONTINUING TO LOCATE TXWY C; A 90 DEG TURN WAS INITIATED; BLUE TXWY LIGHTS LOCATED IN MY VIEW; BUT COULD NOT SEE YELLOW CTRLINE STRIPE. THE TXWY WAS A REVERSE HIGH SPD REQUIRING 135 DEGS OF TURN RATHER THAN 90 DEGS. APPROX 33 FT FROM CTR OF TXWY; ACFT LEFT HARD SURFACE AND CONTINUED INTO OPEN CULVERT (DRAINAGE DITCH) 43 FT FROM CTRLINE OF TXWY. ACFT SUSTAINED LITTLE DAMAGE AND WAS PULLED OUT BY CERTIFIED MECHS ON NIGHT DUTY. ADDING TO PLT'S VISUAL PROB WITH NO LNDG LIGHTS; WAS 'SEA OF LIGHTS' TO S OF THE ARPT (CITY OF LAS VEGAS) WHICH MADE IT IMPOSSIBLE TO DISCERN DIRECTION OF TXWY. THIS SIT COULD HAVE BEEN PREVENTED BY: 1) OPERATIVE LNDG LIGHTS. 2) MORE TXWY LIGHTS TO COUNTERACT 'SEA OF LIGHTS' TO THE S. 3) CLOSING IN A VERY DANGEROUS OPEN DRAINAGE CULVERT. REVERSE HIGH SPD TXWYS ARE INHERENTLY PRONE TO INCIDENTS OF THIS NATURE BECAUSE PLTS ARE NOT USED TO 135 DEG TURNS; L SEAT VISIBILITY DURING A R TURN AND POOR VISIBILITY OUT OF A BEECH BONANZA.