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 checkpoint

In 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.