Ehto is correct and this is the way. I'll go further and say that if someone is tailgating you and it's pissing you off, generously let them pass. Literally pull to the side of the road if you must.
Everything I've read points toward larger margins of safety (longer distances, slower speeds) being safer.
See e.g. https://publications.lib.chalmers.se/records/fulltext/252480...
For example, the specific law in California: https://leginfo.legislature.ca.gov/faces/codes_displaySectio...