The Milford Road is closed today due to a rock fall …govt.nz/projects/milfordroad/RoadStatus.do
I know I harp on about this constantly, but please - late May through the end of Oct - it is best to take the bus to Milford rather than drive.
Even in fine weather the road has a high accident rate, more so in the winter with vehicles slipping off the road.
The road is subject to ice, snow, avalanches, rockfalls, flooding and slips and it is usually impassable several days through the winter. If you drive into Milford and the road closes, you then need to work out not only how to get yourself out, but also how to get your rental car out. A flight out could cost each person several hundred dollars (the last figure I heard when the road closed was over $700). Plus the car rental agency will charge a similar figure or more for having to retrieve the abandoned vehicle.
If you bus to Milford and the road closes then the tour company will pay for your evacuation and you will be returned to where your trip started - Te Anau or Queenstown - and you can then resume your travels.
Please plan wisely and travel safe :)