Tracking congestion levels is often the most visible, direct way for drivers to understand how roads are functioning and a key indicator for transportation officials to evaluate what system changes might be needed. Without timely, consistent measurement of it, said Dan Fedderly, executive director of the Wisconsin County Highway Association, it is hard to hold the DOT accountable.

"The whole MAPSS program is, in very simple terms, to rate DOT's performance. So once they start changing the parameters around that then it becomes difficult to rate their performance," he said. "I suspect partially it's due to the fact that it's not a metric they're going to do well on based on some of their other policies."

Christian Schneider, spokesman for the DOT, said the change has "nothing to do with any of that" but instead has to do with "how the feds are reporting to us."According to the agency's July MAPSS report, which was released last week, the agency said the congestion metric will be replaced with "new measures and targets that align the way state DOTs and Metropolitan Planning Organizations, MPOs, assess performance of Interstate and Non-Interstate National Highway system routes, freight movement on the Interstate system, traffic congestion and on-road mobile source emissions."