For those that are unfamiliar. In short it is a push-to-talk broadcast, public channel, communication. CB stands for Citizen Band.

In Europe, I remember the same frequency, 27 MHz being used for early RC cars. Not sure if EU truck drivers used this too, but it is available and caused runaway RC cars as it was unreliable to use that band. 40Mhz didn't have that issue, but perhaps it was not allowed for regular/unlicensed use...