I have always wanted somebody to explain how freeways slow to a crawl without an accident or other large “event” blocking one or more lanes.  Apparently traffic planners call this situation a “shockwave”.

Traffic Funnel

Shockwave basically describes a situation in which you are forced to slow down on the highway without seeing what’s ahead causing the change in speed.  Once you get in position to see further ahead, traffic begins to pick up and speeds are returning to normal.

Not only was that news to me, but I didn’t even know there was a job called “traffic planner”.  I mean, it makes perfect sense for the position to exist – I guess I just overlooked that aspect of urban planning.

Here’s the full graphic.  If you already knew this then you are certainly a better person than I am.