When David Clark slips behind the wheel of his Jeep Patriot to help another cancer patient get to the doctor’s office, he’s doing it in memory of his late wife, Ginny. It’s been four years since she died of multiple myeloma, and Clark has spent that time as a volunteer driver for the American Cancer Society’s Road to Recovery program. So far he’s logged about 30,000 miles driving patients to appointments and treatments, the equivalent of crossing the United States 10 times. He’s not reimbursed for gas, tolls or his time, but the 74-year-old Clark said helping others is reward enough. “When people say thank you, that’s the payment,” he said.