The rate is roughly on par with all personally-owned cars and somewhat lower than for conventional taxis and limos (about 23.6 percent). The worry, as you might guess, is that app-based hailing services aren't held to a higher standard.

There are also signs that the companies don't strictly enforce their policies on vehicle age. While Uber and Lyft both say a car shouldn't be more than 10 years old, Over 40 cars in King County came from the 2007 model year or earlier.

Uber and Lyft told CR they'd taken steps to tackle these recalls. Uber, for instance, blocks those cars with the most serious open recalls and reminds drivers to fix the rest. Lyft said it worked with lawmakers to regulate vehicle safety. This still leaves many cars on the road with lingering safety issues, though, and CR found that neither company had a concrete policy on recalls.

We've asked Uber and Lyft for additional comment. Lyft reiterated its earlier statement, noting that drivers had a "strong personal incentive" to address recalls as it kept their families safe. It's evident that some ridesharing drivers don't act on that incentive, though, and that could be serious if it leads to a crash or an avoidable injury.