I know you need trash bins around your park to prevent it from becoming a garbage dump, but do you need trash bins in queue lines? Or does the sim behavior of littering or puking stop when in line?
Sims refuse to litter queue lines. However, they will use trash bins placed in queue lines, and if the trash bins are kept empty, nearby sims will receive a green thought about how clean the nearby area looks. Puking still happens in queue lines regardless of trash bins, requiring a janitor to patrol the queue lines every so often.
NB: For some reason, the Park Inspector does not check trash bins placed in queue lines, so you can receive "clean park" rewards despite the trash bins in your queuess looking like a set pieces for the movie Wall-E.