T-Mat

T-Mat was a transmat network that had been established on Earth by the mid 21st century and was run by Travel-Mat. T-Mat cubicles were used as a reliable and cost-effective means of mass-transporting goods all over the world; it seems likely that Travel Mat was the name of the corporation or syndicate that established and ran the network.

The development of T-Mat ultimately led to the abandonment of manned space programmes, with the only launch vehicles remaining being those required to place satellites in terrestrial orbit. It apparently never occurred to anyone in charge that the transmat link between Earth and the moon might one day catastrophically fail beyond the capacity of the moonbase personnel to repair. The Ice Warriors exploited this weakness when they took over the base as a beach-head for their ill-fated invasion of Earth; a corollary of this compromise of the network was a disastrous collapse of global food distribution. (DW: The Seeds of Death)

In the aftermath of the invasion and the Thousand Day War, the T-Mat network was replaced by the Interstitial Mass Transit System. (NA: Transit)

Behind the scenes
According to The Brilliant Book 2012, a book that contains non-narrative based information, history would remember the T-Mat as causing the end of the First Great and Bountiful Space Race.