Yesterday evening I happened to find myself driving next to a truck en route to Detroit carrying some of cars for the filming of Transformers 3.
The small black cars are souped up Chevrolet Sparks that have been
previously identified as the revamped (and hopefully less annoying) versions of "The Twins."

The orange racing stripes designate that this may serve as Mudflap's alternate mode
This has not been officially confirmed. In fact, Michael Bay has
explicitly denied the rumors.

The Chevrolet Spark is the production version of the Chevrolet Beat Concept, which served as Skids' vehicle mode in
Transformers: Revenge of the Fallen.
The small beat-up yellow car is the Datsun PL150, which has been rumored to be a Bumblebee downgrade.

This vehicle was first seen during filming at the Milwaukee Art Museum
earlier this summer.
The film is scheduled to continue shooting at the former
Packard Plant in Detroit over the next couple weeks.
I pissed off a lot of people on the I-94 East expressway to get these pics!
Thanks to TheJake for shooting over this report!