Haroon, Paranoia is about the best way. I drive down the middle of the road just to buy some time IF one jumps out.

Some theories on those whistles are that it scares the deer into running. Sometimes in front of you.

If you tap your horn, they will sometimes run. sometimes stand still. I've read many books on deer and how to keep them out of my garden and off my car grille. All the books say is that they are fairly unpredictable and Deer will eat almost any plant depending on their desperation.

I drive slower and hope for the best. Many people drive fast past me until they have a close encounter, over the years, it's amazing how many drivers have smartened up and slow down in those Deer infested ares.

Two years ago I spotted 5 deer on the road. I came to a complete stop, one ran out of the woods and right into the side of my car. I was a bit cranky, here I saw them, stopped and still got nailed. Grrr.

Be careful out there.