Where does the "I brake for" idiom come from? [closed]

I am familiar with how I brake for is being used nowadays, but am puzzled as to where this idiom comes from.

I can imagine a possible origin, say a particularly popular campaign where stickers with a specific "I brake for…" message were given, but haven't been able to find anything about this.

First off, note that the idiom is "I brake for…", not "I break for…".

I imagine it's a reference to cautionary signs placed on the back of certain vehicles. For example, in the US, it's common to see signs like this on school buses or service vehicles:

This vehicle stops at all railroad crossings

This vehicle stops at all red lights

This vehicle makes frequent stops

So a cautionary sign like

I brake for squirrels

Would be superficially similar—warning others that the vehicle may make a sudden stop if a squirrel happens to cross the road—although it's primary goal is to alert others to the driver's special love of squirrels.

This was later extended to "I brake for X" where X is anything the driver feels special affection for or attraction to even if there is little or no possibility of encountering it while driving (e.g. "I brake for smurfs").

The cautionary sense of the idiom may still apply, for example in the bumper sticker "I brake for tailgaters", which clearly does not indicate any kind of affection.

I believe this originated sometime in the 1980's (I don't have a specific reference other than memory) with "I brake for children" becoming a fad ("Baby on board" followed soon after.).

Numerous wags then ran with it to create hundreds of variations.