You also have good points. As it happens, near my metro area is a park which does indeed have a children's railroad that both crosses and then parallels a major bike trail. And it's absolutely adorable.

The point re: rubber rolling resistance and pollution is well taken. But I don't think the air resistance is negligible here. I realized now that the linked article doesn't describe the speed of this monorail, so I had assumed it was something like a sauntering 30 kph (18 mph), which if available 24/7/365 from rural areas into the urban core and had consistent on-time performance, that'd be excellent.

But this other article lists the speed for these pods as 60 kph (37 mph). That's kinda terrifying for a pod, where just the gyro components weigh 650 kg (1433 lbs), and definitely implicates air resistance. At that speed, the gyro had better be robust enough to counter sudden winds that would threaten to tilt one pod into the path of an oncoming pod.

Now that I think of it some more, on a horizontal curve, roads will widen the lanes so that vehicles won't side-swipe each other. And tracks are set farther apart than on straightaways, for the same reason. But the pair of rails? They're always 1435 mm (4 ft 8.5 in) apart, so will the pods be designed for a maximum curve speed and angle, or will passing be disallowed on curves?

Finally, I will concede that requiring two way pod lanes would definitely be a success story. But seeing as they're planning to use abandoned trackage, even a single-track railroad will already provide two "lanes" for their pods for free. If they had right-of-way that doesn't have existing track, it's not clear if their plan is to install a single rail.

EDIT: I forgot the other article's link: https://update.phoenixcontact.com/en/balancing-act-on-the-rail/

It's a plausible idea, although admittedly it only solves one of the automobile-specific drawbacks and leaves the other issues unaddressed. Road trains show that coupling separate vehicles together yields efficiencies for the few, large prime movers, when compared to several small engines. Moving vehicles by rail is the most straightforward way to reduce friction to enable higher speeds.

But designing a road/rail pod that operates in two speed regimes would be difficult if neigh impossible. Consider crash-worthiness: a road-going pod doing 30 kph (18 mph) does not require substantial crumple zones (or at all) but the same pod on rails doing 120 kph (75 mph) will have to be at least tested to similar standards as passenger railcars. It's a strange beast to optimize for two very different conditions, like how airplanes are designed to be either sub-sonic or super-sonic, exclusively. Instead, something like the Amtrak Auto-Train which carries the pods at higher speeds would have all the benefits and nearly none of the downsides.

But going back to the benefits of this idea: platoons solve the issue of poor lane utilization due to spacing between vehicles fore and aft. Coupling is platooning with zero space in between, which also nearly solves the car-to-car communication issue, since they're now all physically connected. The same applies identically to rail, so the efficiency gains from lots of small pods to large platoons would be realized.

The problem that remain, though, are that these pods still need to traverse their destination: there must be pod roads, pod parking spaces and pod parking structures. Then pods will compete with active transportation and their lobby will seek to monopolize public spaces to the detriment of everyone that's not in a pod. Finally, zoning laws will enshrine the pod into ordinances requiring an obscene and arbitrary number of pod parking spaces by business type, inducing demand for pods when walking, bikes, buses, and trains would have also fit the bill.

All that has changed is that the pods can more efficiently flood the urban core and take up space. The 1960s American freeway building spree did exactly this with automobiles, and most cities have yet to recover.

It reduces the need for freeways without hurting mobility at the origin/ destination.

You are 100% correct, with the caveat that mobility is not hurt compared to automobiles. If the standard for public transport is to achieve automobile levels of mobility, we have already lost the game.

Sadly, monorails require different rails which are taller and thicker this would still apply to a smaller pod style device. I do not see how they could ever keep this balanced on these rails, and don't think the rails would hold up anyways. Additionally, the loop sidedness of the weight distribution seems to me like it can create major issues when the rails have been designed under the idea that it would be more or less equal on both.

This seems like just another person trying to reinvent the wheel because us Americans hate rail, even though the us was built on rail.

Yes, it's regrettable to see public money is wasted on this kind of projects instead of being spent to really improve the public transport infrastructure. Although, in Germany, it really isn't bad. But still.