Older drivers are prized because they usually own their own cars, have adequate auto insurance and, according to insurance statistics, have fewer crashes. Uber’s collaboration with Life Reimagined, a group that helps people navigate life transitions, provides access to the group’s 1.4 million members through online and in-person workshops. Through the alliance, Uber offers a $35 incentive for those who sign up to become drivers and drive 10 trips.

Molly Spaeth, a spokeswoman for Uber, said the company had enlisted nearly 600 drivers as of this month with its AARP collaboration.

Uber and Lyft — which said it did not track the ages of its drivers — and their supporters contend that on-demand employment lets companies provide work without the costly rights and perks like overtime pay and vacation time, that attach to full-time employees.

Besides, David Plouffe, an Uber board member, argued, most drivers work far less than full time. As many as half drive only 10 hours a week, he said in a speech in November, and 61 percent, or nearly two-thirds, have other job commitments.

But Uber does not break out the exact percentages of full-time and part-time drivers. Some drivers who work full time complain that in addition to not having benefits, they must work longer hours to earn a living wage, especially after Uber last year cut the rates it charges passengers.

Drivers in Seattle who belong to the App-Based Drivers Association, a group allied with the Teamsters union, won the right last month to negotiate pay and working conditions. That makes a lot of sense to full-time drivers like Musse Bahta, 42, who said he had to spend more time on the road since Uber lowered the per-mile fare to $1.35.

“You have to work close to 50 hours a week to survive,” he said, pointing out that he has to subtract payments for his new Toyota Camry, gas and maintenance from his gross income. “If I did Uber on the side, there would be no complaints.”