Can I deduct mileage for driving to and from work? Sometimes I have to drive my car to different locations and sit in my car for hours at a time.

I work in transportation and have to go to several different locations between DC, MD, and VA.  Most of the times a vehicle is provided but sometimes we have to go in our own cars.  We may be sitting in one location in our cars for up to 12 hours.  You have to idle the car for hours during that time for heat or ac.