DANVILLE — As Cindy McCaffrey finished her early afternoon bike ride, she pedaled along sycamore-lined Deer Meadow Drive less than a mile from her home. Heading the opposite direction, an 86-year-old neighbor was returning home in her Lexus.

McCaffrey never finished her ride. And the elite triathlete, rock climber and equestrian would never ride her beloved bicycle again.

“You hit the bicycle,” a witness told the confused driver after flagging her down when she failed to stop. “Where did she come from?” the driver asked, according to a CHP report on the May 20, 2013, accident.

When her husband, John McCaffrey, heard about an 80-year-old driver crashing through a Livermore gym last month, killing a woman inside, the memories flooded back. He remembered his vow outside Cindy’s intensive care unit to push for a state law requiring older drivers to get road tested to renew their license. He remembered how the effort fizzled, as senior advocates and other stakeholders refused to support any such legislation.

“At the time, I was full of piss and vinegar. I thought I could have an impact on testing,” McCaffrey recalled. “Then, ultimately, I realized there isn’t anyone with the courage to bring this bill forward.”

As drivers reach 70 years of age, their rates of accidents and fatal crashes per mile driven rise and sometimes surpass levels of the youngest, most accident-prone drivers. Drivers 85 years and older have the highest rate of fatal accidents per miles driven of any age group, according to the Insurance Institute for Highway Safety.

But attempts to stiffen driver’s license renewal requirements based on age have failed in California and elsewhere. Senior organizations question the data or label such efforts age discrimination, too expensive or unnecessary.

When Cindy’s friend, Terry Mullen, asked then-state Sen. Mark DeSaulnier for help kick-starting legislation mimicking Illinois’ law requiring a road test for drivers over age 75 at each renewal, he was told to get support because previous attempts for such a bill were quickly defeated.

Mullen, a 72-year-old Danville resident, said he tried to work with AARP. He eventually received an email from Nina Weiler-Harwell, associate state director of advocacy for the senior organization: “AARP policy opposes age-based driver testing that is not based on scientific evidence.”

Calls and email requests for comment from AARP were not returned.

Some experts caution that fixing the problem is not simply a matter of stiffening testing requirements.

“This is one of those complicated issues that people get very upset about and want an easy solution. There isn’t one,” said Elizabeth Dugan, associate professor of gerontology at the University of Massachusetts, Boston, and author of a book on aging and driving, in an email. “It will take a public health effort to educate older drivers about threats to driving fitness, health care providers being alert to medical threats to driving threats, family members talking about a difficult issue, and alternatives to driving (e.g., a Senior Uber type of service). We aren’t there yet, but are moving closer.”

Dugan added that her research on the topic showed that road tests or more elaborate testing had no effect on preventing accidents among older drivers and are expensive to implement. She also said a recent pilot experiment by California found no benefit in increased vigilance and screening of older drivers.

The last major legislative effort in California was in 1999, after a Santa Monica teen was killed by a 96-year-old driver who last took a road driving test in 1918. The bill was quickly shot down.

The only California driving law specifically targeting seniors is a rule that after age 70, motorists must renew their license every five years in person, rather than by mail. For those appointments, drivers receive a vision and written test but no road test unless a DMV employee deems it necessary.

Illinois is the only state that requires seniors to take road tests. The state also makes renewals more frequent as motorists get older, and once they reach 87, drivers must renew their license every year.

DeSaulnier had to end his efforts with Mullen and McCaffrey when he left for Congress, but the 63-year-old lawmaker still thinks it’s an important issue driven by a large, older demographic.

“I’d like to think people from my generation would be open to this,” he said.

State Sen. Steve Glazer’s office says it has begun to look into the issue.

Jessica Cicchino, a senior research scientist with the Insurance Institute for Highway Safety, stressed that while driver accident rates rise as people age, overall rates for seniors have been trending downward. Also, requiring seniors to renew their licenses in person appears to correlate with lower fatality rates based on the limited data available, she said, while road-testing requirements did not appear to affect accident or death rates.

“There needs to be a balance of making sure unsafe drivers are off the road, with people keeping their mobility and independence,” Cicchino said.

Mullen and other advocates for new restrictions say the problem will only get worse as the number of Americans over age 70 is expected to rise to 52.7 million in 2030, including about 46.6 million licensed drivers, more than double the number of older drivers in 2011.

A 2012 federal study found that almost two-thirds of all pedal errors — where the driver mistakes the gas pedal for the brake, similar to the Livermore accident — involve young and elderly women, and the highest percentage was women 75 or older.

The argument that younger drivers are just as dangerous, Mullen said, is a separate issue. Generally, younger drivers have all the cognitive and physical capabilities to be safe drivers but often are inexperienced, immature and lack good judgment, he said.

While a road test with younger drivers may not reveal those problems, such a test would work best for identifying senior drivers with diminished faculties, Mullen said.

“The legislation we were proposing wasn’t anti-aging; it’s pro-aging. It’s protecting them from impairments they might not know they have,” Mullen said.

On a sunny Belmont day in June 2010, a block into Ed Mitchell’s bike ride, he was struck by an 89-year-old woman making a left turn into her courtyard. He was tossed over the car, blowing out his knee and cracking his helmet.

“Why did you hit me?” the woman asked him as he lay on the ground, Mitchell recalled.

During depositions, the driver’s daughter said she’d long tried to get her mother to stop driving, but she wanted her independence and restricted herself to just going to the grocery store or doctor.

“Oh, God yes,” said Mitchell, who has trouble walking because of lingering knee issues, when asked if testing should become stricter for older drivers. “As a result of doing tests, we’d be getting these bad drivers off the road and then we’d be forced to find a way to get transit services to them. … At least we wouldn’t continue to pretend the problem doesn’t exist.”

It’s the fear of losing independence that drives opposition against new laws, Mullen and McCaffrey said, and yet Cindy McCaffrey has lost much of hers.

After the 2013 Blackhawk accident, she spent more than two weeks in an induced coma and the past two years receiving rehabilitation and therapy to learn to walk and talk.

She now wears hearing aids, has numbness from her right hip to right foot, and can’t taste or smell foods. Her balance is terrible, eyesight diminished and she has had numerous mouth surgeries.

The former elite athlete tried jogging again last November for the first time since the accident and broke her knee cap and tibia when she fell on a curb. She tried again Sept. 21 but broke her wrist when she fell after her right leg went numb. She had surgery Wednesday.

The woman who hit Cindy had her license suspended more than a year after the accident. The CHP found the woman at fault, but no criminal charges were filed.

The Livermore driver’s license has also been suspended, according to the DMV, and police are still investigating that case.

“I’m angry, but I feel sorry for the lady that hit my wife,” John McCaffrey said. “I wouldn’t want to spend my last years on Earth burdened with the knowledge that I had impacted someone’s life like this.”

Contact Matthias Gafni at 925-952-5026. Follow him at Twitter.com/mgafni.