Enforcement under the Radar
Photo radar, as part of Boulder's neighborhood traffic mitigation program, is designed to decrease speeding violations in neighborhoods and school zones, a laudable goal. It has indeed reduced speeds.
In 2008 the city got heat for its radar site on North Broadway; the van was stationed in a no parking zone, spewing noxious smoke into the adjacent bike lane. In response, the city added a sign under the no parking sign excluding police vehicles and replaced the van with a less stinky one.
There is another reason to question the North Broadway location, which is 50 yards short of where two lanes merge into one. Although drivers should be prepared to merge without speeding, local factors can make obeying the speed limit difficult. The lane loss is not marked well in advance, and occurs shortly after a pedestrian crossing and a steep hill with limited sight distance.