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They're hardly low emissions once you consider the full lifecycle as North Carolina State University did[0] (units from article converted to less insane CO2-eq g/passenger-km.. or maybe it should be oz/mi?):

  257  Personal car
   25  Personal electric bike
    5  Personal bike
  126  Shared scooter
  118  Shared dock-less bike
   51  Bus /w high ridership

The shared scooters/bikes have lots of CO2 from lifetime, redistribution, and charging (scooters). Somewhat counter-intuitively, a popular bus has less than half the CO2 belching impact of a shared scooter.

[0]: https://iopscience.iop.org/article/10.1088/1748-9326/ab2da8

2 comments

That's not a reasonable comparison. All other transportation methods are measured solely by tailpipe emissions or energy consumption, like they're some kind of natural geological phenomena. The CO2 emissions for shared scooters/bikes, according to Section 2.4, table 1, additionally include mining and processing the raw materials, manufacturing, shipping over the Pacific, shipping across the entire width of North America on a truck, collection, distribution, and maintenance.

The unmentioned takeaway of this study is how important it is to incentivize improved manufacturing methods that are closer to markets, as well as maintaining existing product (if it's reasonably efficient) to extend service life. Materials, manufacturing, and shipping are responsible for vast CO2 production, largely because there's a strong cost incentive to move that manufacturing to locations with inefficient production and/or loose controls that are far from the product's market. For reducing overall CO2 emissions, improving CO2/KM alone is literally only half of the picture.

It is not so counter intuitive when you consider that popular bus carries a lot of passengers. I'm not sure what is the high ridership, but even average of 20 means per passenger rate is fraction of others.