A few people have asked me these questions in the last few weeks,  and I didn’t know the answer.    I presented my question to the Wisconsin DOT,  and received this response from Ryan Mayer, Traffic Safety Engineer for the SW Region – Madison office.    Instead of forwarding the answers to those who asked the questions,  I’m posting them here in case other people have the same questions.

Question 1:  Do slower speed laws apply in Wisconsin construction zones when no construction workers are present (such as after their workday for example)?

The speed limit reductions set in construction zones may or may not change during the course of a day (when workers are present).   It depends on how traffic is being affected by the construction workers/their equipment/traffic control items like drums and barricades.   If a work zone is expected to impact traffic significantly differently when people are there working vs. when they are not the speed limit can change.

The easiest and best way for drivers to tell what the regulatory speed limit is set at is to pay attention to the black and white speed limit signs.   Those are the ones that are enforceable and would be altered if the speed limit changed throughout the day.

Question 2: Why isn’t the Beltline’s speed reduced in the construction zones? there are no “45mph” signs up. Is speed automatically reduced even if no signs up?  

Speed is not automatically reduced, as I stated above.  If the black and white speed limit signs say 55 (like on the beltline) then the speed limit is 55.   The reason the speed limit is not reduced on the beltline this summer is because it was determined that a lower regulatory speed limit would not be appropriate.   The construction staging was designed to accommodate a high rate of speed and the traveled lanes are wide enough for people to generally feel comfortable driving 55.

It can be counterintuitive, but in some cases lowering the speed limit could cause more problems than it would solve.   If people feel comfortable driving 55 and we were to lower it to 45, most drivers would ignore the signs and drive at the rate of speed they feel comfortable.   A smaller portion would drive 45 because that is what the signs say, and this creates an issue with people driving at different speeds.   It can lead to tailgating, unsafe lane changing/passing and can also impede the flow of traffic.