My friend Brian asked me recently, "how do you define being 'buzzed' by a discourteous driver?" In answering his question, I want to add a few "best practice" type tips for all my motoring pals.
Personally, I would feel "buzzed" by a motorist if they passed within 3 feet at speed. So, a full speed pass outside 3' may not feel like a buzz, and a slow pass at 3' may not feel like a buzz.
If you feel like you have to "squeeze by," don't. It won't be comfortable for you or the cyclist.
Legally, in NC, vehicles must maintain 2' separation. This is not bike specific, it pertains to all vehicles.
Typically, a 3-4' pass is the minimum distance that is comfortable for both motorists and cyclists. In fact, many bike advocates lobby for 3' passing laws in their states, and several states have adopted such regulations.
But, honestly, the "best practice" in this regard is to give all the room you've got beyond 3-4'. If the whole oncoming lane, or a center turn lane is available, pull completely into it. If there is a solid center line, but no oncoming traffic, cross the line to make the safest pass. In addition to creating the safest and most comfortable pass for you and the cyclist, your wide pass will encourage motorists behind you to do the same.
In many places, it may be technically illegal to cross a solid center line, but the smart advice I learned from the i am traffic folks holds here, too - don't let paint think for you!
Big thanks to Brian for asking! It's incredibly cool for a motorist and casual cyclist to ask, not just about how much space one *has* to give, but also how much space is best for cyclists' comfort.