Photos as promised; all of the following photos are from Main St (Business 151) in Sun Prairie, from the ramps at US 151 east to Walker Way. WisDOT/Dane County maintains the signals at the ramp terminals, while Sun Prairie (and their contractor), maintain the rest.
First up, the intersection at Walker Way. Up until 2011, this was the standard for the city of Sun Prairie, similar to other municipalities in Wisconsin:
The next intersection, Main St and O'Keeffe Ave was reconstructed within the past year, at the same time the Main St ramps with US 151 were reconstructed. For the time being, vertically-mounted signals on trombone arms are the new Sun Prairie standard:
Close-up of the mounting:
Lastly, the WisDOT design standards, at the ramp terminals with US 151:
WisDOT is apparently still using up older stock of LED modules. Note the different lens on the amber signal below; it has the WisDOT first-gen dot matrix appearance, whereas the newer ones are the 'incandescent-look' LED lens. There are a mix of old and new LED modules at these ramp terminals. Not all are amber, most are green, and a couple red's.
The new "bubble-lens" (assuming it's to prevent snow build-up); only found on monotube-mounted signals. Note that not all of the signal assemblies have these for some reason (missing in the middle assembly):
The new, standard egg-crate visor pedestrian signals:EDIT: