public OnGameModeInit()
{
       SetTimer("VehicleHealthBarUpdate",500,true);
       return 1;
}

forward VehicleHealthBarUpdate();
public VehicleHealthBarUpdate()
{
       for(new i=0;i<MAX_PLAYERS;i++) if(IsPlayerConnected(i) && IsPlayerInAnyVehicle(i)) {
               new Float:health; GetVehicleHealth(i,health);
               SetProgressBarValue(Barid1,health); //Value must be Float
               ProgressBarUpdate(Barid1);
       }
}