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/