Anywhere you're performing tasks related to your job is considered your “workplace” for the purposes of workers' compensation coverage. That means if you're on a job site outside your regular location, at dinner with a client, running errands for your boss, or on the way to or from any of these places (in your own or a company-owned vehicle), you'd be covered.
However, you're NOT covered during your commute to and from work, or if you leave work for a lunch break. But other tasks during the work day when you're “on the clock” and acting at your boss' direction are included.