Recently I wrote about the new 40MPH speed limit as you enter Woodstock from the west on South Street. My opinion is that the 40MPH speed limit may not be enforceable, because a driver is given no warning that the speed limit is dropping 15MPH.
When a speed limit drops more than 10MPH, a driver is entering an Altered Speed Zone, and the driver is to be so informed (or warned). This is done with a Reduced Speed Ahead or Speed Zone Ahead, white regulatory sign with black letters and a smaller speed advisory sign below it with the new speed limit.
This afternoon I spotted such a sign on westbound IL 173 as I entered Chemung. In this case, the speed limit drops from 55MPH to 35MPH, a decrease of ..... hmmmm, let's see ... 20MPH. Aha, so speeds can be reduced more than 10MPH. This sign was probably installed by IDOT, since IL 173 is a State highway.
This is the type of sign that needs to be installed in McHenry County on eastbound South Street, as a driver approaches the 40MPH speed zone within Woodstock. Why not just do it?