It seems like the kind of thing that you see around here a lot more these days. As you approach a light, there's a back-up. It turns out someone has realized that, although they were in the right lane, they needed to turn left at the light, so they are now slowly making their way across three lanes of traffic to get to the left turn lane. Everyone behind be damned -- they don't matter.
These accidents-waiting-to-happen don't just arise out of the blue, they happen because someone has just received new data, just processed their location, and realized that they were poorly positioned to respond to it. This is driving by GPS at it's worst.
The ability to anticipate what will happen, to expect the possible and position yourself accordingly, is something that sometimes seems lost in the Silicon Valley we live in. Predicting these moments is a combination of strategy, planning, and experience, any one of which will enable you to do better than an ugly last minute "oh shit".
But even in the face of those unexpected events, there's no reason that you can't make a graceful adaptation -- recalculate your route and adapt to your new course with a smoother transition. Remember HP's tablet effort? So your tablet sales sucked, does that mean that try to work your way across three lanes of traffic in order to reach your, "we're not going to do hardware anymore" left turn?