Let's reformulate it as a railroad problem. In the proposed hypothetical, if you effectively ban self driving cars until they're literally flawless, 50 people per day will be killed by human drivers every day. If you pull the lever and allow imperfect-but-better-than-human self-driving, 25 people per day will be killed by by autonomous vehicles.

As a reference point, non-suicide gun-related deaths total ~45 people per day.

What moral principle could possibly justify not pulling the lever?