Crowd control is an important job, especially at major events and meetings. Barricades, temporary barriers, bollards, wheel stops and safety mirrors are just some of the devices that can be for crowd control, and they be put in place for parades, protests and street events.
Disorder can break out quickly, and at important events it has to be handled and dealt with quickly. Public events are tricky, and it can be difficult to plan the amount of individuals who are going to turn up, forming a crowds.
There are many tactics to control crowds, and it is up to the organisers of an even to make sure the crowd is controlled sensibly.