Lyric discussion by Clownshoes 

Cover art for Bicycle lyrics by Unknown Mortal Orchestra

Definitely a metaphor to Albert Hofmanns 'Bicycle Day' experience as per onetwothreefo's comment above...the narrator is caught up in an LSD moment (after taking a big dose and mixing with other drugs).

"Was it great, no disease That will get you taken by a squad car right to the a&e"

Sounds like he was tripping balls on his 'ride' and the cops came and spoiled the fun

@Clownshoes I think what he's referring to there is that it is NOT like "other" kinds of drugs that will make you end up there. Replace the word "disease" with "drug" and you'll see what I mean