Heading south on the 57 Freeway from the 210 through San Dimas, you’ll see a mileage sign that may make you do a double-take — which is appropriate since it’s got a redundancy: “Corona na Fwy.”

I noticed this a while back on my first drive on that route in quite some time and thought, Did I really see that? Then last week, a local official who commutes daily on the 57 happened to email me about it.

He says Caltrans closed the offramp to the 71 (Corona) Freeway a year ago for some work and covered the exit sign. When the offramp was opened and the sign uncovered, “lo and behold, the sign read ‘Corona na Fwy.’ It looks like they put a new Corona sign over the old Corona sign, but didn’t cover the last ‘na’ in the sign underneath,” he says.

That’s the sort of attention to detail we expect from Caltrans. I wonder, though, why the new “Corona” takes up so much less room. Maybe the sign read differently, like “71 Corona Fwy”? Whatever the reason, it’s amazing, but dispiriting, that the mistake has stood there for a year, give or take.

“I keep thinking that one day some Caltrans worker will notice it and tell someone to fix it,” my source says. “But in reality I like it because every time I drive under that sign, I can’t help but giggle thinking that it is a Caltrans tribute to Sha Na Na: Coro Na Na. I also wonder if I’m the only one who notices the sign typo as I’m whizzing by at 75 mph.”

Doubtful. For one thing, traffic rarely moves that fast.

Google Street View, rather hilariously, documents the misspelling, from whence the above image came.