Obedience training... ugh!

I've been struggling to find a way to effectively train Emery to obey me. The problem here is not the severity of the punishment, but the swiftness and consistency of the punishment. If I give her a command and she doesn't obey and I punish her 90% of the time then she's always looking for that 10% when she can get away with it. Also, I've discovered that if I let myself give the command three or four times before she obeys then she doesn't obey me when I give the command mildly, then with more determination in my voice she still doesn't obey, then with even more determination. In fact, she doesn't obey me unless I sound extremely threatening (or if I actually give threats) and then only reluctantly. This is unacceptable behavior which was illustrated with terrifying poignancy when we were out of town the other day. We were in a parking lot on our way to the van. I was holding Warren in my arms and Jimmy was on the other side of the van getting ready to get into the driver's seat. Emery was tagging along behind. I saw a pickup truck driving our direction and I called to Emery to come here now. She thought it would be a fun game to play chase so she turned with a grin and ran directly in front of the oncoming vehicle. I cried out in terror. Luckily the driver of the truck was paying attention and slowed down, coupled with the fact that Jimmy, with adrenaline pumping through his veins, sprinted to her and picked her up faster than I thought was humanly possible. So I made a promise in my heart that I would step up her obedience training. So I waited with determination in my heart for her to disobey me so I could show her how serious I was. But she's really a pretty good little girl and she didn't disobey me very often. Maybe only three or four times a day. And if I wasn't watching her very closely then I wasn't able to deal out the punishment swiftly enough for her to really get the idea. It is close to impossible to be 100% consistent when you have a baby in the house! So either I wasn't watching close enough to catch the transgression in time, or I was holding a sleeping baby in my lap that I didn't want to wake, or my hands were wet and soapy from doing dishes and I couldn't get to her, or some other problem prevented me from reaching that 100%. So I went back to the drawing board. Clearly my original plan wasn't working. I needed a new strategy. So I devised a new plan that I'm currently working on. And this plan is working better than any of my previous attempts. Instead of waiting for her to disobey me, I give her an arbitrary command and then punish her if she doesn't immediately obey. I also, of course, praise her and thank her when she does obey. But I have always done that in all my strategies. So I'll wait till she gets involved with her toys, then I will say, "Emery come here." in a mild but clearly commanding tone. If she doesn't immediately drop what she's doing then I walk over to her and mildly (not angrily) administer her punishment. Then I walk back to where I was and repeat the command in the same tone. If she still doesn't obey then I repeat the process over again. If she does obey then I praise and thank her for obeying. Since I started this strategy (yesterday) I have never had her disobey me more than once. I also give her other commands. "Emery, pick up your books and put them away." "Emery, get the stool and wash your hands." And then the standard, "Emery don't touch mommy's watch." "Emery, hold still while I comb your hair." "Emery don't push buttons on the TV." etc... This strategy is working! She is obeying me with more consistency now. And the surprise of the century... she is happier doing it! She is a happier girl when she knows that I'm in charge and she obeys me cheerfully and without reservation. I hate this part of parenting... but I'm glad I finally landed on something that is going to work for our family. Everyone in the family will be happier when the children cheerfully obey the parents.