Barricades, vertical panels, drums, and cones in construction zones are known devices.
a. blocking

Barricades, vertical panels, drums, and cones in construction zones are known as channelizing devices. They are used in construction and maintenance work areas  to notify drivers or passengers of unusual or potentially dangerous conditions in or near work areas.
A barricade is a portable or fixed device having from one to three rails with appropriate markings. It is used to control traffic by closing, restricting, or delineating all or a portion of the right-of-way.Drums are most commonly used to channelize or delineate traffic flow but may also be used singly or in groups to mark specific locations.

Answer made of magnesium alloy;

It my nizzle