This simply isn't true. By the mile they have a worse safety record than other cars in their class (mitigating factors: where they're driven and who drives them). You might be referring to Tesla's marketing statistic that there are fewer accidents per mile involving autopilot - typically engaged in ideal driving circumstances - than when it's switched off, or across all other drivers. But that's not very meaningful data. Some would argue that citing marketing figures from a company with a track record for obfuscation and dishonesty as "the data" (and really, there isn't much better data available to the average person) is an indication we're not being careful.