Remember this question?
When you look at this photo what do you see that might make a dog nervous?
Sometimes the unexpected "scary" thing your dog shies away from can be on the same walk you take every day, and sometimes it takes a little detective work to figure out what "spooked" your canine companion. In this photo you can see several possible "scary" candidates. There is a large industrial building, a parking lot, elevated light rail tracks and a rooftop garden with a flagpole.
You might immediately come to the conclusion that the elevated tracks are the culprit. They were a little spooky even to me when trains first began to operate in 2009. However, if you have worked on habituating your dog to the elevated tracks and the trains moving over them, chances are it's not the train.
In an instance like this where you may have been walking this same route for 6 months and your dog has never shied away before, look for the "novel" or any change in the environment.
Have you guessed what the scary thing is? It's the flagpole! Notice how the flags are flying in the wind. The combination of a waving flag and its hardware clanking is enough to change the environment from safe to scary in canine consciousness.