DRG FLT, THE PLT NOTED A NEGATIVE READING ON THE AMMETER & CYCLED THE ALTERNATOR SW, BUT TO NO AVAIL. BEFORE LNDG, SHE ACTIVATED THE RWY LGTS & DISCUSSED THE WNDS WITH A DEPG PLT. A COMPLETE ELEC FAILURE OF THE ACFT OCCURRED AS IT WAS ON DOWNWIND TO LND AFTER THE TWR HAD CLOSED. CONSEQUENTLY, ALL EXTERNAL LGTG & COM RADIO IN THE ACFT WERE INOP. A VEHICLE DRIVER WAS MAKING A RQRD INSPN ON RWY 32. THE DRIVER SAID SHE MONITORED THE TWR FREQ USING A HAND HELD RADIO & HEARD A DISCUSION, BUT DIDN'T HEAR EXACTLY WHAT WAS SAID. SHE SAW THE RWY LIGHTS ILLUMINATE, BUT THOUGHT THEY WERE ACTVTD BY THE DEPG ACFT. SHE ANNOUNCED HER FLD PSN & INTENTIONS USING THE GND CTL FREQ. THE PLT LNDD THE ACFT ON RWY 20 & BGN THE ROLLOUT AS THE VEHICLE DRIVER WAS ON RWY 32, CROSSING RWY 20. SUBSEQUENTLY, THE ACFT & VEHICLE COLLIDED AT THE RWY INTXN. THE ACFT'S ALTERNATOR & VOLTAGE REGULATOR WERE REMOVED & TESTED, BUT BOTH WERE FND TO BE OPNL. THE OVERVOLTAGE UNIT WAS NOT RECOVERED & THE REASON FOR THE LOSS OF ELEC PWR WAS NOT VERIFIED.