By the numbers: How often self-driving cars disengage

This week, California's Department of Motor Vehicles released the latest data from companies testing AVs in the state, including the total number of self-driving miles logged and how often human backup drivers had to take control of the wheel.

Why it matters: The so-called disengagement reports are a proxy for how AV technology is progressing. But the data is self-reported and often misinterpreted, so it's dangerous to draw comparisons.

What they're saying:

• Wired writes that like many standardized tests, the reports miss a lot. They are poor tools for understanding how well this technology works and how each company’s progress compares to that of their competitors.

What we know:

• Waymo is by far the leader, with 1.2 million miles driven in California in 2018.
• The former Google self-driving car unit's vehicles drove an average 11,154 miles without driver intervention, nearly double 2017's performance.
• GM's Cruise also showed strong improvement, tripling its miles driven before a human took over to an average 5,205 miles.
• Zoox, Nuro and China's Pony.ai were well-behind, but not as far back as Apple, whose on-again, off-again AV efforts ranked dead last with a handoff to the human driver every 1.1 miles driven.
• The 48 AV developers that tested their tech on public roads collectively drove 2.05 million miles between December 2017 and November 2018, up from 500,000 the year before, per Wired.

The bottom line: While the improvement is good to see, and shows AV technology is progressing, it's clear that fully driverless cars are not yet ready.

Go deeper: Check out the reports from all 48 AV companies tested in California here, and read Chris Urmson's analysis of AV performance metrics for Axios Expert Voices.