P.M.
Restaurants and parking lots are not natural habitats for young children, and you'll find that most, if not all, families who take their children to such places have experiences like yours, at least occasionally.
I've watched this "not listening" phenomenon with great interest for decades now, interacting with many young families in my neighborhood and religious community. What I think I see is that the parents don't listen to the children, either, and the kids are imitating their parents. If Joey wants a snack, or to have a few minutes to examine some object, or needs to get up and move, or take a stroll across a parking lot to learn what is safe, too bad, if the parents want him to do something else. They are too busy to pause to hear his need. He learns to do that in return.
Same thing with sassing or back-talk – kids really are doing a childish version of what they hear from their parents: "Joey, no." "Joey, you get over here right this minute!" "Joey, stop that." "Joey, don't use those bad words." "Joey, put that down." "Joey, no." "Joey, do that again and you'll be in trouble." "Joey, knock it off." "Joey, what did I tell you?" "NO, Joey!" And on, and on. Parents really don't hear the tone they use with their kids.
I sounds to me like Oliver is checking the truthfullness of what you tell him, so it's really important to tell him only the truth. You tell him the cars will hit him – he finds out twice that he can go into the parking lot without getting hit – even when he's not holding your hand.
Part of that is just the natural scientist in young children, the exploration of cause and effect – a critical skill that contributes to the survival of the child, IF he doesn't "git hisself kilt" first. So it is critical for parents to be careful about what we say. If we want to be a respected authority in our children's lives, we would do well to be truthful and accurate and respectful. Always, always, always.
Will we succeed in that? No, we'll goof. So apology is another critical art we need to demonstrate for our kids if they are ever going to learn genuine and heartfelt apology.
So, all that is groundwork in helping him develop social skills. And so is keeping your expectations of his abilities age-appropriate. Toddlers have extremely short attention spans, little impulse control (and virtually none when they are tired and hungry), can seldom sit still for more than 10—15 minutes, and don't like restaurants, because they don't comprehend why adults will sit for an hour and do something so boring as eating and talking. So there will be a few bites of food they may or may not like, and then total boredom, or getting in trouble, which is at least a little less boring.
Let me suggest a few books that you will find invaluable over the next several years. Dr. Harvey Karp's THE HAPPIEST TODDLER ON THE BLOCK, Faber and Mazlish's HOW TO TALK SO KIDS WILL LISTEN, AND LISTEN SO KIDS WILL TALK, and John Gottman's RAISING AN EMOTIONALLY INTELLIGENT CHILD. I have watched the empathetic parenting taught in these resources transform family life for several young parents of problem children.