Could it be Optimus Prime?
I am satisfied that this is an imposter and not Optimus Prime.
Update for confused readers: As the dogs and I were walking the other day, we had just come to "mailbox corner" when I realized the big truck was bearing down on us. Nellie was savvy enough to react to the tone of panic in my voice and come to safety on the bank, but I had to convince Bess. The big truck turned our corner very close. (I'm not sure the driver ever saw us.) Apparently Bess was impressed because as we walked back home -- same direction as the truck -- she stayed at my knee, and when she did finally move from me, she crept along -- every step controlled. The truck had parked in the neighbor's field -- was there to haul away the hay bales -- and it did seem ominous, peeking over the rise to watch us. As we approached, Bess' curiosity got the better of her and she cautiously moved in to investigate. Apparently she learned that it was inanimate and no threat when silent.
And Nellie? Timid Nellie has never been afraid of big machines -- just little ones, like lawnmowers and weed eaters. "Aw Bess!" she said, "Quit being a silly goose. It's just an old truck."