This post peaked my interest again and I went looking for the rules. I know that the City has a pretty wide interpritation of control (see page 2), this is spelled out in the actual law. I do know that they consider e-collars control as well, but that is not in the law.
So if the dog is in a public place it has to be in your control: Voice, Leash, Box, etc. So things are looking good so far in this group of well trained truck bed surfers as they drive down the public streets.
Oh Noes! What is this?
In Chapter 8.55.010 Cruelty to Animals (almost at the end), Section A, paragraph 5 it is says
"Prohibited acts. It is unlawful for any person, with criminal negligence, to:
5. Have an animal within, on or attached to a motor vehicle under conditions that may endanger the health, safety or welfare of the animal, including but not limited to insufficient control or extreme temperature.
a. A peace officer is authorized to remove an animal from a motor vehicle at any location when the officer reasonably believes there is a violation of this section."
So you may have "control" of your unleashed or uncrated dog in the open bed of your truck, but it is up to the officer to make the call about you having "sufficient" control. Now think about the thousands of posts on the intertubes about the "reasonablness" of peace officers in today's society, and keep an extra $75 in your wallet to pay the ticket.