Here is a sample of the varying rules across the nation governing drivers’ licenses for older adults.

DISTRICT OF COLUMBIA: Standard license renewal is every eight years. Starting at age 70, drivers must renew in person and bring a doctor’s certification that they’re medically fit to drive.

FLORIDA: People 80 and older must renew their license every six years, compared with every eight years for younger people. Also, people 80 and older must pass an eye exam with every renewal. Florida also allows confidential reporting of a possibly unsafe driver by anyone — doctor, law enforcement, relative or bystander. Officials may ask those drivers to submit medical reports from their doctor or to undergo testing at a driver license office.

MARYLAND: All new licenses last for eight years, regardless of age. However, an eye exam is required starting at age 40 for every renewal. The Motor Vehicle Administration said lengthening the renewal period would save millions of dollars.

MICHIGAN: Licenses last for four years for everyone, with no older age requirements. Anyone may report a potentially unsafe driver to the Secretary of State’s office, and authorities may require that person to pass driving, vision or other tests. The department receives about 300 such requests a month — mostly from law enforcement, followed by family members — but doesn’t track them by age.

MONTANA: Drivers over 75 must renew their licenses every four years, instead of every eight years for drivers 21 to 75.

NEW JERSEY: Licenses are renewed every four years, with no special provisions for older drivers.

All drivers are supposed to have their vision tested every 10 years, but the Motor Vehicle Commission concedes that program has never been fully implemented. Currently, it is piloting a program with eye-care professionals that would allow drivers to mail results of an exam to the agency.

Doctors are required to report certain health conditions to the licensing agency, but other people also can report possibly unsafe drivers of any age for a review.

NEW YORK: Licenses last eight years, with no special provisions for older drivers.

The Department of Motor Vehicles can re-evaluate a driver of any age based on a specific reason, such as a driving incident or action reported by a doctor, police officer or observer. It also can restrict licenses to such things as daylight driving.

OHIO: Licenses last four years, with no special provisions for older drivers.

The state operates a web site — http://www.dmv.com/oh/ohio/senior-drivers — that explains some requirements older drivers may face if they fail standard vision tests or report certain health conditions.

PENNSYLVANIA: Licenses are renewed every four years, with no special provisions for older drivers.

The state Department of Transportation essentially audits drivers. About 1,900 randomly chosen drivers a month, all over age 45, are required to get a physical from their own doctor and an eye exam, either from licensing officials or an eye doctor, before they can renew a license. It also fields about 22,000 reports a year of possibly unsafe drivers from health providers, family members and others.

WEST VIRGINIA: Licenses are renewed every five years, with no special provisions for older drivers.