Road block

A random road block is a general term for a military and police road block that is part of a strategy to prevent unauthorized access or to apprehend terrorists, insurgents or hostile forces.  A random road block is usually set up by mechanized troops or SWAT teams often using armored vehicles. 
A random road block is set up to achieve an element of surprise.  In this way it differs from road blocks set up in permanent locations such as entry roads to towns or bridges and tunnels.  Often, A random road block is a set up on a stretch of road that keeps its hidden from oncoming traffic until they have no choice but to stop or any attempt to reverse is immediately obvious. 
The unit setting up the A random road block must have with it all the materials necessary to construct the road block. The unit may use a vehicle or several vehicles to partially or totally block the road.  They might reinforce the road block through the use of barbed wire, spike strips or other objects that would disable a vehicle trying to force its way through.  In some instances, units can be equipped with a mobile road block that can be deployed in minutes and provide an adequate deterrent.
As this type of road block is inherently dangerous to those manning it, armed guards will usually be position in close proximity and others in covering positions.  Depending on the security risk that required the setting up of the road block, other weapons such as machine guns and even RPG's might be deployed for use.
This type of road block allows for the vetting of both vehicle and pedestrian traffic through it. Those wishing to pass through must present valid I.D's and submit to body and vehicle search.  Personnel manning such a road block must be constantly on the alert for suspicious behavior as today's terrorist will think nothing of blowing himself up if he can kill some of the "enemy"
Ideally a random road block must be up and working no longer than 15 minutes after the unit's arrival in order to achieve the element of surprise.  In high risk and volatile situations, covering troops will be stationed 50 to 100 meters away on both sides of the random road block.  Another force might be in a concealed position to provide backup if needed.  An additional security element that might be incorporated into the random road block is a forward spotting team that can give advance warning to those manning the road block of approaching vehicles and a threat assessment.
This type of road block is generally in place for only a few hours.  The reason for this is to avoid giving the enemy time to organize and attack and also to prevent him from knowing where the next