Most states in the USA have laws allowing you to run a red light. Normally after 3 cycles at least AND if the way is clear. Sometimes it's 10 minutes and if the way is clear. I think both of those apply in Iowa State Law IIRC (used to work for the state and spent some free time browsing the state code... your tax dollars at work).
BTW- it's not usually about the weight of the bike. Most traffic sensors are not weight triggered and don't have a weigh scale in the pavement. They are coils of wire usually in the shape of the lines cut in some pavement where the sensor was added. The metal mass of the vehicle, mainly the engine, is what triggers the sensor. I found that even with a lighter bike as I have now, with less metal mass, I can stop in a certain place over that wire loop and trigger the light. If I sit right in the middle of the loop or am not stopped over it at all then I sit. What amazes me is the cars and SUVs that stop way out into the intersection past the loop and they sit there longer than they should because they passed beyond the sensor where the planners didn't put one out into the intersection. If I stop with the main engine block sitting over the forward or rear diagonal wire line of the sensor I get better results.
Of course there are always one or two lights that just don't trigger unless the metal mass is as much as a SUV anyway so I revert to state law for waiting at the light.
Oh, and I did try the big magnet trick way back in 2001 but that was a bust. No difference using a large computer hard disk voice coil magnet... the kind that practically needs a crow bar to pull it off of stuff it attracts to (and then another one to pull it off the crow bar).