[Burridge]

pawn Code:

new RCcar[MAX_PLAYERS];

should be

pawn Code:

new RCcar[MAX_VEHICLES];

Then

pawn Code:

RCcar = CreateVehicle(464,x,y,z, 0, 0, 3, 999999999);

should be

pawn Code:

RCcar[vehicleid] = CreateVehicle(464,x,y,z, 0, 0, 3, 999999999);

This means you'll need to define vehicleid in that command. Then

pawn Code:

PutPlayerInVehicle(playerid, RCcar, 0);

also becomes

pawn Code:

PutPlayerInVehicle(playerid, RCcar[vehicleid], 0);