Ask a teenager – or the parent of a teenager – and they can tell you with remarkable precision about the requirements for getting a driver’s license. There’s a bright, clear line over the horizon for kids. They know the whens, whats and whys.

At the other end of life, there are no lines, bright or otherwise, to determine when it’s time to hang up the car keys for good.

The facts are undeniable. As a person ages, reflexes and response times get slower, hearing and eyesight decline, muscles become less flexible, strength fades. But it doesn’t happen at once and not everyone is affected in the same way. Some 80-year-olds have perfect vision. Others are active and athletic. There’s just no telling.

For most of us, the decline will be gradual and we may not even perceive it, although others likely will.

Giving up the independence that goes along with driving is tough to do. It’s made even harder in a mostly rural state like Maine where there are few options for public transportation and family and friends might be scattered out over great distances.

Even a discussion of the issue is wrapped in emotion. Tell a parent that he or she is not fit to drive and be prepared for a fight. When it comes to driving, freedom isn’t just another word for nothing left to lose. There’s a lot that can be lost.

That’s why the Independent Transportation Network is such a tremendous idea.

As The Associated Press reported earlier this week, the Independent Transportation Network helps seniors stay mobile without having to drive or beg rides from family and friends. The network, which started as a graduate school project, accepts donated cars from older drivers. The value of the car goes into an account, which is charged when the seniors get a ride from volunteer drivers. It’s based on the idea of a reverse mortgage. Rides are scheduled, with discounts for advance notice.

According to the AP, the network provided 15,200 rides last year in Portland, and pilot programs are in the works for four other cities around the country. Sen. Susan Collins is seeking a five-year, $25 million grant to fund an expansion and is also working to create tax incentives for seniors to trade in their cars for an account with the service. The funding should be approved.

ITN developed in response to a tragedy. Founder Katherine Freund’s 3-year-old son was hit, while playing in the front yard, by an 84-year-old driver who thought he had hit a dog. As a graduate student at the Muskie School of Public Service at the University of Southern Maine, Freund began work on the issue of sustainable transportation for senior citizens.

There are more than 20 million drivers in the United States older than 65. That number is predicted to increase to 40 million by 2020. According to statistics from the National Highway Traffic Safety Administration, 34 drivers 65 or older were killed in 2004 in Maine. While more young drivers, those between 16-20, died (36), the numbers illustrate a serious problem facing older drivers.

With an aging state population, transportation options are too limited.

The state needs more stringent and frequent tests for older drivers, but until there is a reliable transportation network, perhaps based on the ITN model, it would be both impractical and unkind to leave seniors stranded in far-flung places without reliable transportation alternatives.