Some of the newer inductive loop detectors at Louisville traffic signals use the quadrupole loops recommended in the website on bicycle-sensitive traffic detectors. You can tell the quadrupole loops by the three parallel black lines in the pavement along the direction of travel (photos of traditional dipole and new quadrupole designs, called "figure 8 loops" on that page). You can see them, for example at the intersections of Pee Wee Reece Road and Taylorsville Road (near Bowman Field - map), E. Liberty Street and Baxter Avenue (map), and Spring Street and Payne Street (map). Unfortunately, the design details of the quadrupole loops in Louisville result in at least half of them (including two of these three) failing to trigger for bicycles. Some that will detect bicycles (such as the one at Liberty and Baxter) require a bicyclist to place one wheel at exactly the right location, often beyond the stop bar. Merely switching from dipole to quadrupole loops does not solve the problem - the physical and electrical details of the loops need to be right.
A couple of years ago, Metro installed experimental bicycle-sensitive loop detectors on Spring Street on both sides of the intersection with Mellwood Avenue (map). Spring Street, a marked Bicycle Route, has bike lanes on each side. Metro installed the bicycle-sensitive loops in the bike lane, which makes sense only until you recognize that a bicyclist heading northwest (toward downtown) on Spring Street needs to merge left into the main travel lane to keep from getting hit by motorists turning right from Spring Street onto Mellwood Avenue. I don't like a design that forces bicyclists to choose between triggering the light and risking getting right-hooked. In addition, Metro never marked the pavement or in any other way informed bicyclists of the purpose or location of the bicycle sensors. Most local bicyclists I know have no idea the sensors exist until I mention them.
This year, a block away and with equally little fanfare, Metro installed pushbuttons on Spring Street/Adams Street at its intersection with Story Avenue (map). A bicyclist facing a red light on Spring/Adams can pull over to the curb, hit the button, and wait only a few seconds for the light to change. (The buttons work.) Alas, this again requires the bicyclist to ride to the right-hand edge of the street. For a bicyclist riding NW on Spring Street, this causes no problem because traffic on the intersecting street (Story Avenue) goes one-way to the left. For a bicyclist riding SE on Adams Street, though, motorists coming from behind may turn right and hit the bicyclist who has just ridden from the curb after pushing the button. To use the button, the bicyclist must take an unsafe position on the road. As with the bicycle-sensitive loop detectors a block away, no signs or pavement markings alert bicyclists to the existence or function of the button.
In all of these cases, I suspect that it would have cost Metro no additional money to install a bicycle-sensitive loop detector as the traffic detector in the middle of the right lane. It would have cost a bit more to add the necessary bicycle logo (scroll to the bottom of the page) to mark where bicyclists should stop to trigger the light. The problem: some traffic engineers don't believe that bicyclists and motorists can ever be trained to accept the validity of a bicyclist riding in the middle of a vehicular traffic lane, even if only at an intersection. It's time to try a well-designed, adequately funded educational campaign to raise public awareness and change behavior of motorists and bicyclists. Sometimes, education can accomplish goals that engineering cannot.