A barrier it’s a physical obstacle what prevents the passage or access to a site. It is usually a wooden or metal fence that, according to the needs, is raised or lowered so that one can, or not, advance.
The difference between a barrier and a siege, wiring or fenced is that the barrier blocks the passage temporarily. These elements have a mechanism that allows them to be moved to clear the way whenever desired.
It is common for there to be barriers in level crossings (that is, at the point where a railway track intersects a street, highway, or other path intended for automobiles and / or pedestrians). These barriers serve to coordinate the transit: When a train approaches the level crossing, the barrier is lowered so that cars cannot cross the track. This prevents accidents. Once the train has passed the level crossing, the barrier rises.
Barriers are also frequently installed in tolls and in the parking lots. In these cases, the barrier blocks the passage until the driver pays the corresponding fee, either to go through the toll or to enter the parking lot. Upon payment, the barrier is lifted.
Some barriers are manuals and they need a person to take it up and down. Other barriers are automatic and have a system and sensors to function without the need for human intervention.
At a general level, anything that blocks or hinders the progress of something is called a barrier. It can be spoken of ice barrier, acoustic barrier, etc. Barrier it is also a surname common in several Latin American countries.