Roadblock
A roadblock is a temporary installation set up to control or block traffic along a road. The reasons for one could be:

Roadworks
Temporary road closure during special events
Police chase
Robbery
Sobriety checkpointIn peaceful circumstances, they are usually installed by the police or road transport authorities; they are also commonly employed during wars and are usually staffed by heavily armed soldiers in that case. During protests and riots, both police and demonstrators sometimes use roadblocks.

References
See also

Road traffic control
Barricade
Boom barrier
Braess's paradox
Illinois v. Lidster
Safety barrier
Traffic break