Kneeling solves the problem that even a low-floor bus still has a floor height of around 30 cm. Due to a need to maintain sufficient ground clearance and the ab

Kneeling solves the problem that even a low-floor bus still has a floor height of around 30 cm. Due to a need to maintain sufficient ground clearance and the ability to sweep over regular height kerbstones (up to 20 cm), you can't get much lower than that, whereas conversely you also can't really raise the kerb at regular bus stops that high (i.e. to 30 cm or higher). Kneeling gets you down to a floor height of about 22 - 24 cm, where level boarding with a 22 cm high kerbstone is just about possible, though still subject to not insignifcant requirements where and how the bus stop exactly can be placed in terms of road geometry. So the basic gist is that kneeling doesn't absolve you from the requirement of getting the floor of the bus as low as reasonably practicable in the first place, and you need both if you want to achieve anything resembling level boarding at all.