This week on The Best of Car Talk, after driving in Massachusetts for the first time, Addie is baffled by the concept of the rotary. Happily, Tom and Ray can explain its true purpose. Elsewhere, is "Backseat Driver Syndrome" incurable? Lani got used to yelling at her husband when he was a stinko driver, but now that he's doing better behind the wheel, she's still nagging from the passenger seat. Also, Christine is wondering if she needs to give up knitting in the passenger seat, lest a deploying airbag turn her needles into projectiles; Jem needs to clean a stuck valve, but the gunk may be the only thing holding his engine together; and even after three alignments, Russ still thinks his car may be headed for a ditch. All this and more, this week on The Best of Car Talk.