In 1934 Lawrence Butterfield picked up Elveria, his date for the senior prom, in his dad’s Model A. For Mr. Butterfield, who is now 89, it was the beginning of two love affairs — one with his lovely wife-to-be and one with his car.

Today, while the Butterfields’ six-decade marriage remains strong, Mr. Butterfield’s relationship with his car is over. His family decided he shouldn’t drive anymore.

In metro Detroit, more than 500,000 people over age 65 either have or will soon face the same dilemma; another one million people will in the next 30 years. For those who don’t have ready access to either good public transportation or a willing friend with a car, this means lives of increasing immobility and isolation.

But thanks to SMART — Detroit’s suburban bus system — the Butterfields can take the Dial-A-Ride van from their Dearborn home to the grocery store, the doctor, or friends’ houses.

“The SMART bus helps us remain independent,” said Mrs. Butterfield. “With more people living longer, staying active helps keep expenses down for taxpayers if people are not stuck in their homes and can do for themselves.”

One big taxpayer expense that better public transit could significantly reduce is emergency medical transportation. Wayne, Oakland and Macomb counties together spend about $37 million annually on ambulance service. But only about half of those trips are actually for emergencies. Many of the rest, proponents say, might be made via the much cheaper Dial-A-Ride or community transportation systems — if the region offered better service.

Although missing his days behind the wheel, Mr. Butterfield says the “SMART bus fills an important gap.”