Law of blindingly obvious consequences?

It appears that that part of the A47 which bypasses Norwich carries a lot of traffic and regularly experiences serious congestion.  The local council decided that in order to decide what, if anything they should or could do about this, they needed more detailed information.  To this end they set up a survey whereby for one day they would record each vehicle using the road and where it came from, where it was going to, and why.  You can imagine what happened can't you?  A massive traffic jam!  But the point is that this apparently caught them by surprise - difficult to believe.