Do you know what the braking distance is for an average car (even as relatively light-weight as a sedan)?

Exact numbers differ, but many sources say it's about ~300 feet (I've seen up to 525 feet) for 55-60 mph. That's actually a lot more than 10 car lengths.

At 40 mph it appears to be around 140-150 ft, which is actually about 10 car lengths.