Thanks to all for the suggestions. Perhaps a bit of experimentation is in order. I've never actually observed any lines or grooves in any of the pavement around here to indicate the whereabouts of any embedded loops.
There seems to be some doubt as to the effectiveness of the use of magnets or magnetic force to trigger the signal lights to trip but I'll give it a shot.
As I already carry a 12volt lawn mower battery for my lights and other accessaries it should be easy enough to rig up a pretty powerful electro magnet that I can turn on an off as needed.
I'll give it a try and see how well it works.
Again,
Thanks and any other thoughts on this matter that have not already been explored are appreciated.