Note: I know nothing about Rav Schwartz and I don't think I ever heard of him before.

Rav Schwartz expressed his dismay at a new trend among frum girls. This new trend is that they ride scooters - korkinets, as they are called in Hebrew. Rav Schwartz says this is a serious breach in the fences of tzniyus.

Rav Schwartz says that every day the Satan comes up with new ways to breach the walls of tzniyus, and the newest method is enticing the girls to ride these scooters, either electric or regular manual (foot powered) through the streets and paths. And it is not just young children, but also young female adolescents, who are otherwise dressed completely in a tzanua style according to all the dictates of halacha - girls who would never consider doing anything against the rules of tzniyus.

Rav Schwartz says that all God fearing women and girls know very well that this is not a chumra or hiddur but is a basic tenet of guarding her honor and tzniyus.

source: Kikar

I admit. While I know that bicycles are a no-no for girls in the Haredi community and Beis Yaakov schools [in Israel] typically do not allow the girls to ride bikes, I was not aware that scooters are also a problem. And I see a lot of girls riding scooters. It seems to be pretty normal and accepted. And it is not new. Maybe in Bnei Braq it is new and maybe there it is not accepted, but it seems pretty common and standard to me.