To the driver ...

... of the maroon truck with "In God We Trust" plates whom I followed from Lusher Avenue to the Prairie Street Kroger:

Since your truck appeared to be fairly new, I thought perhaps you hadn't fully familiarized yourself with it's communications equipment. On the left side of the steering column you will likely find a lever. Pushing that down will tell other people that you plan to make a left turn, like when you turned onto Prairie from Lusher. Similarly, you can push the lever up and those around you will know that you plan to make a right turn, like when you turned into Kroger from Prairie.

You'll note that neither of these actions does anything for you personally, except perhaps to increase the goodwill of others toward you.

You're welcome.