Britney's Evening Drive ...

Brit was back in the saddle after a late-afternoon wardrobe change -- she spent most of the afternoon driving around with her bodyguard in her white convertible Mercedes, then she made a pit stop at Micky D's, another pit stop at home (and a quick change), and then hopped back in her ride for a little night drive!

So ... Britney driving around all day ... again, not big news. But there were a couple interesting details we spotted in these pix:

1. 1) Britney's butt looks absolutely AMAZING! and she is in work-out gear so that may have something to do with her newly-toned derrière


2. 2) she's jammin' to Janet!

CHECK OUT THE GALLERY OF BRIT'S DAY AND NIGHT YESTERDAY RIGHT HERE!

more pix inside too ...