Probably the same problems that are making (rail) infrastructure building 10x more expensive in the US than in Europe.
It's not that the knowledge is inaccessible, the problem is that the not-invented-here syndrome compounded by administrative red-tape, powerful counter lobbies and greedy actors make those projects prohibitively expensive.
It's not that the knowledge is inaccessible, the problem is that the not-invented-here syndrome compounded by administrative red-tape, powerful counter lobbies and greedy actors make those projects prohibitively expensive.