My husband and I got a tandem over the weekend. We test drove it in a parking lot. Within 30 seconds it was clear that transparency and communication are of utmost importance -- as is true in relationships. When he stopped pedaling, my pedals stopped while I was still in forward motion; my feet flew off the pedals. When he started again, I wasn't ready; reflexively I moved my feet out of the way of the spinning pedals.
Did I get mad? No. Do couples get mad over these types of things? You betcha! Timing, plans, being heard (being seen), control, etc. can be a very big deal.
I calmly said that I need to know when he will stop or start pedaling since the pedals were connected. We laughed, and started again, using words this time. "On three . . . one . . . two . . . three." It was really fun. I'll let you know how it's going.