If it were me, I'd respond: "Okay, I'll follow you to the nearest public bathroom, but you're still getting the citation."

Someone pulled that on me once, but I saw them pass a few public bathrooms as they cut around a line of cars in traffic to get to the turn lane a bit faster by going down the wrong way of the roadway, so they were obviously lying.

You might have more luck with your lie among lazier/less discerning/dumber cops, it's true.

- Ex-cop