Speaking as a nobody with half a brain
I would happily argue that a tandem is a vehicle and it's an argument I'd win.

ve·hi·cle (v-kl)
n.
1.A device or structure for transporting persons or things; a conveyance
(unclestinky, Tue 21 May 2013, 19:50, 1 reply)

And a rollerskate?

( drimble he'd been white, he'd been black, Tue 21 May 2013, 19:52, closed)

two
to escape from the Gendarmes when covered in the blood of your children
(unclestinky, Tue 21 May 2013, 20:03, closed)