Indian motorcycle snowmobile conversion. Kits like these were designed to be put on and off the bike in the fall and spring when it was too cold to ride and too warm to snow.
I’ve seen this method reproduced on bicycles, including a sidecar tallbike that wasn’t as deadly as anything else tall with more than two wheels. So it can carve. It’s not that hard to pull off- all you need is articulation (which would normally cause the thing to fall down) but then add an armature that places the outrigger wheel in the proper position (you can see it below the axle). Unlike Ackerman steering, I suspect a 90 degree angle for the arm is used. Make it adjustable to find the best ride.
(Source: enginedynamicsinc, via bikefreak)