One special benefit of using near surface subways is that the transfer vehicle could take people up at ground level. This as the following advantages:

The transfer vehicle has natural potential energy at ground level, this assist in accelerating it down the slope to join the subway and in slowing it down during approach to the next station.

Existing stations could be reused as acceleration and deceleration lanes for the transfer that vehicle to join the main line.

The quality of journeys that people perceive would be improved as journeys would start and finish in daylight. Threatening and unpleasant underground environments would be removed. The perception of rat race travel during peak times would be softened due to less congested ground level platforms space.

Journey times would be non stop, the time taken to navigate through tunnels and escalators in attempting to find the correct platform are factored out. [This can represents a high proportion of journey time particularly with old, neglected and confusing station layouts in cities like London].

 Delays at ground level stations should be reduced through having a higher frequency service, and greater intermodal integration possibilities.

Overhead

Doing research on the net I discovered my idea of putting two trains on one monorail was not original. However the system proposed is possibly less visually intrusive due to the small size of the track.