One of the worst railway bottlenecks in the United States is just west of Fort Worth, Texas, where major east-west and north-south lines cross on the level at a location known as Tower 55.

Given the American passion for long, slow, double-stack container trains and the like, the potential for delays is considerable.

The obvious solution is grade separation. The local highway geography does not favour a rail-over-rail bridge, so a 3 kilometre long rail-under-rail trench is proposed.

The trench would be 10 metres deep and 18 metres wide, and would run east-west. Construction would necessitate reconstruction of some local streets: local people oppose this.

Building it north-south rather than east-west would achieve the same objective, and would have the advantage that it would be less disruptive to the community and could be built on railway owned land. However, it would dislocate rail traffic in the short term while it was being built, and would be more expensive operationally in the long term because of the gradient which would face northbound trains.

Maybe a solution is to deck over the trench - for parkland, for commercial development, for community facilites, for car parking. Sure, it would need good ventilation because of the use of diesel traction, but that is manageable.

Certainly it would be good to see a solution to the problem: it is currently very disruptive to the two main freight railways, BNSF and Union Pacific, as well as to Amtrak.