Would I write...

Question

While driving east, the forest became denser.

or

As I drove east, the forest became denser.

Also, do I capitalize East?

Answer 1

Both of your sentences are correct.

East is not capitalized in either of these sentences because it means a direction.

Answer 2

I will go with Ms. Sue's answer. It could still be either way around.

Answer 3

.The trees did not do any thing as she moved. The better sentence would be the one using "as"