Spike strip

Generally, the strip is composed of a collection of 35-to-75-millimetre-long (1+1⁄2 to 3 in) metal barbs, teeth or spikes pointing upward.

[1] They are historically a development of the caltrop, with anti-cavalry and anti-personnel versions being used as early as 331 BC by Darius III against Alexander the Great at the Battle of Gaugamela in Persia.

[citation needed] In the United States, five officers were killed deploying spike strips in 2011, having been struck by fleeing vehicles.

It has steel spikes to puncture tires, and becomes entangled around the front wheels, halting the vehicle.

It is designed to reduce risk to crowds by making the vehicle skid in a straight line without veering unpredictably.