@Override
    public int processIncomingVehicle(int arrivalTime) throws ArrivalTimeException
    {
        
        if(arrivalTime > 24 || arrivalTime < 0)
        {
            throw new ArrivalTimeException("Must enter a valid number 0 - 24.");   
        }

        /*
         * Adding vehicle to the database with a new/unique vehicle id &
         * arrival time.
         */
        Vehicle v = new Vehicle(getNewVehicleId(), arrivalTime);
        
        /*
         * Creating a temp vehicles array to copy/replace ouyt of date array.
         */
        Vehicle[] temp = new Vehicle[vehicles.length + 1];
        System.arraycopy(vehicles, 0, temp, 0, vehicles.length);
        temp[temp.length-1] = v;
        vehicles = temp;
        
        return v.getVehicleId();
    }