On CA-128 heading towards Alexander Valley - a road with nominal traffic but not a ton of shoulder - sort of an annoying place to ride but it's the only connector from Calistoga/Knights Valley to Jimtown and on to Healdsburg, used most by cyclists coming to and from Chalk Hill Road.
A truck comes up behind us. We are riding single file but there are 13 of us, and with the winding nature of 128 and the oak trees blocking the sightlines, it's tough to pass a group. The driver waited patiently - not a huge lift as we were going 25 MPH - and when we got to a passing zone, including a dotted yellow, the driver went into the opposite travel lane and proceeded to pass.
The driver of a Jeep Cherokee following behind then tried to pass the truck on the right! The truck completed his pass of our paceline and started to merge back into his lane and was almost taken out by the Jeep that was zipping up along the inside!
The driver of the Cherokee slammed on the brakes, resettled himself, and then proceeded to accellerate and pass the truck on the double yellow.
I have a new helmet cam but it was not in operation, unfortunately.