Cones and Barrels

• A common sight on many highways, plastic traffic cones and barrels act as one variety of barrier. They aren't terribly effective in a physical sense, but they act as a warning as well as a symbolic barrier. The advantage to cones and barrels is that they're comparatively cheap, and much easier to move than more permanent traffic barriers.
  
  

Type I and Type II Barricades

• Type I and Type II barricades are permanent, fixed barricades that are used to funnel traffic on roads that are under construction. These barricades form long walls that close off lanes of traffic, and they're very difficult to move. Often these barriers are shaped like triangles without points, with wide bases that narrow to flat tops to enhance their stability.
  
  

Type III Barricades

• A Type III barricade is used only when closing off a road completely. These barriers are drawn across lanes of traffic, or they may extend from one curb to another. These barriers often have signs on them that say "Road Closed" or other information about the nature of the road being impassable. Since these barriers may be hit head on, they're heavier than Type I and Type II barricades and are a great deal more immovable.
  
  

Materials

• Traditionally, all three major barrier types have been made out of concrete, usually reinforced with steel rods. As technology has advanced though, barriers have often been made of plastic, reinforced with metal bands and weighted down with water. This is especially common among Type I and Type II barricades, which have more of a guiding than a stopping effect. Lighter materials are also more mobile, which means that barricades may be moved more easily than in the past.
  
  

Crowd Barricades

• While most barricades are meant to stop vehicles, there are some that may be used to stop foot traffic as well. Type I barricades (particularly the water filled plastic ones) may be used. Saw horses are also a common tool for stopping foot traffic. Additionally, measure such as ropes, signs and plastic tape may be used to impede those on foot.