DOT Physical Exam Ontario at Truck Stop in Ontario, CA located at 4265 E Guasti Rd, . The hours of operation for this clinic are not known, however most walk-in clinics are open daily and for extended hours. DOT Physical Exam Ontario at Truck Stop appears to be individually owned and operated and not part of a larger network of clinics. There are, however, 2 walk-in clinics within 20 miles of Ontario in cities including upland and Montclair.