The zombies can at the most move at a fast stumble, like falling forwards but any healthy human can easily outpace them by walking. They have strength in numbers so that's what you have to watch out for.
In this case, what is your plan? What will you do if faced with something like that?
You have all the resources of a modern city at your disposal, electricity and water is slowly being cut out as the plants are overrun by zombies as well (you have 2 weeks or so of them left). The city is currently being evacuated but no major invasion by the zombies yet, but news over the radio/internet/television has reached you and you have about a week to prepare before your city is overrun.
This isn't a game, I just want to know what your plans are in the face of something like that, so enjoy and discuss