When you hail an Uber or Lyft, it's often without a second thought. Maybe you're heading home after a night out or running late on your way to the office. But how safe are the cars you‘re trusting to get you from point A to point B?

A recent investigation from ConsumerAffairs tested the tire tread on 1,200 tires in three cities -- Chicago, Dallas and Miami -- to see how well rideshare drivers maintain their vehicles.

As a baseline, ConsumerAffairs noted that most car experts say that tires with a tread depth of less than 3/32 of an inch are unsafe for the roads. So how did the ridesharing startups stack up? Inspectors found that 12 percent of Uber cars, 14.7 percent of Lyft cars and 16 percent of city taxis were driving with at least one unusable tire.

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Unexpectedly, the study also found that personal vehicle tires were better maintained than Ubers, Lyfts and city taxis. Chicago rideshare cars had the safest tires, with 100 percent of Ubers and Lyfts driving with intact wheels.

Uber and Lyft did not respond to a request for comment.

Automotive expert Lauren Fix, The Car Coach, says that it's incumbent on ridesharing passengers to approach vehicle safety like they would with their own cars, right down to wearing a seatbelt, being on the lookout for broken tail lights and bald tires and keeping tabs on navigation.

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"If I get into a car and I see ‘check engine’ lights on all over the place and a cracked windshield, I just get out of the car, report it to Uber and usually get a credit," Fix tells Entrepreneur. "It rarely happens -- usually I'm in brand-new cars -- but I've done that with cabs, too." She advises that if you see anything that seems off with a car or just have a gut feeling, let that particular ride pass you by. "Why would you put yourself at risk?"

As far as ridesharing startups making certain that the cars in their fleets are well maintained, "I think that's a selling point," Fix says. "It's a PR move on their part to say, 'We've got all of our vehicles up to date. If there is a recall, we've taken care of it. If it needs maintenance, we've done it.' To me, if I saw one of those companies doing that, I'd more likely use that company."