Unlike ships, STOL or VTOR aircraft; and / or off road motorcycle or 4X4s, ET3 requires fixed tubes along the entire route of travel. Therefore there is a minimum demand required for economically viable operation whereby the energy and time savings justify the construction cost of the tubes. This limitation of ET3 is shared by trains and canals. Many jurisdictions impose this limit on automobiles too. The cost of standard double tube ET3 guideway is greater than the cost of a residential street (or country dirt road), but about 1/4th the cost of a typical 4 lane freeway.
As with roads and HSR, the cost of ET3 is a function of design speed and topography. Alignment becomes critical at higher design speeds (thousands of km/h). Higher speeds dictate underground infrastructure in tunnels, subjecting ET3 to many of the disadvantages of tunnels for the high speed routes (at least three times the cost as above ground ET3) Also it is very expensive to build ET3 across deep water.
Therefore ET3 will not likely serve remote islands, or an isolated cabin in the woods (unless along an advantageous route between population or resource centers).
The optimal economically feasible cargo load weight (800 lb (365 kg passenger, 900 lb (410 kg) cargo) of ET3 is limited compared to a: truck, cargo aircraft, train, barge, or ship capable of carrying loads of many tons. This limitation is shared by automobiles, SUVs, and motorcycles. ET3 is not viable for transporting adult elephants, however the ton/hour capacity of ET3 can be greater than a double track heavy rail line. Our research shows that about 94% of cargo can be accommodated by standard ET3 capsules 1.3m diameter X 4.95 long, (more if disassembly is allowed). By contrast a standard 40 foot shipping container can accommodate about 98%.
Finally, there is an energy and time overhead for a capsule to enter / leave the tubes through an airlock and recharge the air system and maglev cooling system. This limits the usefulness of ET3 to trips longer than about 10km (6 miles).
See the attached file showing ET3 constraints.