The totally asymmetric simple exclusion process (TASEP) with a defect site models traffic jams, mRNA translation slowdowns, and bottleneck effects in driven diffusive systems.
TASEP: particles hop right with rate p, blocked at a defect site (red) with reduced rate q. Depending on α, β, p, q, the system exhibits three phases: low density (free flow), high density (traffic jam behind blockage), and maximum current. The blockage creates a shock wave — a sharp density discontinuity — that diffuses but maintains its identity.