Direct conveyance is the accessing of raw element energy via a spike of pure tralaticon driven into a Root of the World or Primal Current. The massive network of roots and currents are connected to the Element Guardians and enable them to control the flow of elements between the planes. The Conduit Cities are located at particular locations, called connection points, where these roots or currents come within reach of humans. As far as anyone knows, there are only these three locations.
This method of accessing element energy directly is only about 10 years old. Before that for many decades, passive conveyance was used, which is much slower and requires many machines working in close proximity to the connection point to produce usable amounts of power. With direct conveyance, the limit of energy draw seems to be the speed at which the Conduit Plant is able to process it for transmission.
Direct conveyance was discovered by accident during a joint city experiment in the Earth City Conduit Plant by an academic named Dr. Baird Silver. His experiment was destroyed by the unexpected power draw, but the results were clear and within months all three cities implemented direct conveyance into their plants.
The results were massive and came quickly. The abundance of cheap energy expanded infrastructure projects of all kinds and trade in raw elements, before a trickle due to the slowness of passive conveyance, blew up overnight. Each city only had access to one element and this trade brought more interaction between them than ever before.
The largest project, recently completed, was the trans-continent, or at least the areas controlled by the Conduit Cities, high speed rail system. Huge pillars support the tracks high above the ground and connect all three cities and some of their outlying settlements. The trains float on cushions of Air supplemented by Earth magnets.