I love the design of the San Francisco “Park at 90 Degrees” car. On one hand it looks like no car still on the road, and yet it’s completely recognizable as a car—even with tires that show through the body.

Based on the dates printed on the signs themselves, sometime between 2005 and 2007, the signs switched from the “rounded hood” design above to the “blunt hood” design below (in an effort to modernize?). The tires also got noticeably squarer. It kind of looks like a warthog from above to me.

Here’s one of the oldest versions of the sign that I’ve found on Flickr, and as you can see, it only dates from 1996. It closely resembles the rounded hood version at the top, but with some slight differences.

I got curious about where this design came from, how long it’s been around, how many incarnations it’s gone through, what car it’s based on? So I decided to contact the Sustainable Streets Division of the San Francisco Municipal Transportation Agency to find out more.

I got a call back from Scott Broady, one of the Traffic Engineers at the SFMTA (and self-appointed sign historian), and he told me that the “Park at 90 Degrees” sign was very likely designed in San Francisco. He says they have card files for all of the signs, and the one for this sign included an index to the original drawing, but he was unable to find the drawing. However, the index number suggests that the drawing dates from 1972. He found it odd that they’d use such an old car design in the 1970s, but it’s also possible that the design was based on an earlier one from the 1950s.

That’s where the trail gets cold. If anyone knows more, or has a photo of an older version of the sign, feel free to email me or leave a comment. Thanks.

Update, 2013-08-09: In response to a query on Quora, Richard Henry thinks it’s a 1950s Ford Mercury Eight Coupe, while Matt Wasserman suggests that it’s a Tucker.