From our local Marx expert, Al Osterud:
Marx made it beginning in 1961 and called it “roadbed track”. The roadbed track was packed with many Marx sets plus was available for separate sale in the Sears catalogs from 1961 through 1965. A straight section of roadbed track was 27 or 28 cents depending on the year and region of the country for the Sears catalog. The Marx long wide-radius straight track was 22 cents in 1961 at Sears while a Marx O-27 regular straight section was 19 cents at Montgomery Ward, so the roadbed track was a premium product. A regular straight section of Lionel O-27 track was also 19 cents in 1961. The Marx HO track with a similar plastic roadbed was 19 cents in 1961. HO Marx track without the roadbed was 13 cents per section the year before.
The roadbed track came only in the O-27 track style. There were prototypes in the Marx factory archives of similar plastic roadbed to fit the Marx O-34 wide radius track, but none was produced. The roadbed for O-27 included straight sections, curved sections, straight sections with an indent for the uncoupler or log-dump actuator, straight sections with one or two notches for the track connectors (lock-on’s in Lionel speak), and a section with the platform for the operating box/refrigerator car. It was simple to make – the regular track was set on the roadbed, and very slight bends to the ends of the ties locked it into place on the roadbed. It is equally easy to replace a piece of rusty track in the roadbed today.
There was another track style in the Marx archives which is even more like FasTrack. It had a plastic roadbed and slots for the web of the rails. Rails were formed with only the tube and the web, but without the bottom flanges which crimp to the metal ties in regular tubular track. The rails were pressed into the slots and a few twists to the flange from the bottom locked it into the roadbed. The resulting rail was just barely taller than the Marx wheel flanges, and it would have been the lowest profile track on the market. It probably would not have cost any more than the regular track to make, and was completely compatible with the regular Marx and Lionel O-27 track. The slot in the roadbed kept the flange tight and the pins would have fit better longer than in regular tubular track. It should have been produced – why it was not is one of the many Marx “failure to compete with Lionel” moments that are very hard to understand today. Lionel Super-O track was new in 1957. If Marx had put a blackened center rail in this proposed track, they would have blown Super-O away.