What are traffic shockwaves and how do they form?

Shockwaves are boundaries between two traffic states traveling through traffic stream. Speed of shockwave = (q2-q1)/(k2-k1) from the difference in flow and density between states. Types: forward-forming (congestion dissipating), backward-forming (bottleneck impact spreading upstream). Queue formation at bottleneck creates backward shockwave; queue discharge creates forward shockwave. Understanding shockwaves helps predict queue lengths, spillback, and recovery times. Simulation models track shockwave propagation for traffic management.