What the heck is a MIRT you ask?? :) Well MIRT stands for mobile infared trasmitter. What can I do with a MIRT?, well they are used on emergency vehicles to go thru traffic and change the lights at certain intersections. Many traffic lights, mostly at busier intersections have an IR receiver on them, so that when a police or fire and rescue vechile approaches the light changes to green for them. These are the plans to build your very own, now mind you this is probably illegal in your state to have, and I assume no responsibility for your dumb ass getting caught with one of them ;) But if you want to build one anyways and play around with it, here goes:
Here is a video that talks about the tech behind it.
Here is the article on how to build your own MIRT.