Driving is definitely an activity that can cause a strain on your eyes. In addition to activities that cause you to focus the eyes for long periods of time some environmental factors can add to the stress placed on your eyes such as brightness and glare. Direct light causes the most glare.
Reducing glare will dramatically reduce the strain on your eyes. Glare is caused by the reflection of light off of surfaces and is a primary cause of eye strain. You can get rid of glare by controlling the light source, the surface reflecting it or by filtering it before it reaches your eyes with window film.
Eye strain can severely diminish the quality of your life. It can also be difficult to diagnose eye strain. Treating it is not that difficult but the best way to treat eye strain is to prevent it in the first place.