The US public transit system according to APTA offsets 6.9m metric tons annually. The NYC subways run on electricity generated from fossil fuels (and some nuclear). They may have a similar amount of passengers but have a lower offset due to GHG emissions. NYC runs a lot of empty trains.

Light rail has a very low acceptance rate in the US, because it is too slow and costs an average of $100m per mile. PRT at 1/10 the cost allows a network that is 10x larger.

ULtra, Vectus have operational systems, Skytran is under development. These systems need engineering and have lower risk than miracle batteries that the PHEV people are struggling to a reach 40 mile range.

I'm not opposed to the NY Subways (I rode them for 10 years) but there is just only one project (2 ave subway) that is on the horizon. NYC can seriously reduce car traffic by an above ground solution not digging. PRT is the only currently viable solution that has a chance in NY city.

Do you really thing they are going to put light rail in NYC? Dream on.
-Realist