Early slotcars were huge, 1/32 and 1/24. HO came out in the late '50's or early 60's by a company called Playcraft. Aurora bought the roadway/highway system from them for the track system more than anything else. Playcraft slotcars are extremely expensive so I've never seen one of their chassis. The Aurora Vibrators are an interesting thing to watch and run. Sooo slow by today's standards. Marx, and Atlas quickly followed. I don't know if any arrangements were made, but I'm glad they all decided to be compatable. Had they all decided to use a different power delivery system, HO slots may have fizzled out in the early 60's. If I had to guess, I'd say one of these 3 or Faller was the first to come out with the RR X-ing, bringing the 2 together. Unfortunately, "HO" slot cars are quite a bit bigger than 1/87. Maybe close to 1/72 for Tjet size, and about 1/68 for the larger AFX chassis. I've been working on and off for a few years trying to make an S scale/HO slotcar RR X-ing. Until then, I'll have to be content with a backround highway system.. The big issues are that slots use DC, and the train uses AC, and never the 2 shall meet. The other issue is the size of the rails is twice that of HO RR tracks, so the cars need to jump them without launching off the track.