The glass is made of two layers of tempered safety glass; this safety glass can be damaged by the impact of a specially hardened steel/metal tip, for example the emergency hammer on buses and trains, or an extremely high impact on a very small area.
When this happens, one of the two breaks but does not burst or lose its integrity due to the structural composition of the glass panels; furthermore, the broken glass panel can be replaced by the local facility manager plus one helper within a short period of time.