Post bus rollover footage found online. On an expressway in Nagoya, Japan, near Tokyo, within about the past day, a bus with passengers overturned in broad daylight, and caught fire. It seems those dividers, that ones that are used to separate lanes of traffic with an object on top of lane markings, augment and other purposes, and have a slope from the base up towards the vertical main portion, may have had something to do with the rollover.
From an engineering standpoint, if a tire clips the barrier right at that slope, it may be enough to keep rolling without knocking the barrier over, while the weight of the barrier might keep it in enough position that it cause a vehicle to be impacted off the ordinary trajectory, in some cases far enough off the trajectory it could cause rollover, spins swerves, etc.

This article may serve at minimal to forewarn that the barriers should have visibility, such as markings when at night, or the tan that blends in in the daytime perhaps reflectors, generally slow the vehicle down when coming up on these barriers that are a close call might help accident prevention due to the barrier itself.