I agree with the above. My TB loves to move! Your best bet is to get her tired lunging before you get on her.
I never have to ask twice for her to move faster. :)
I don't have much experience with horses. The only TB I've ever worked with is mine.
I don't lunge her often, but if I do I don't even bother asking for walk until she gets some energy out of her. She would walk, if asked, but I found she works much better when we do it with a positive attitude.