The LWR model treats traffic as a compressible fluid. Conservation of vehicles: ∂ρ/∂t + ∂(ρv)/∂x = 0, with fundamental diagram v(ρ) = vₘₐₓ(1 − ρ/ρₘₐₓ). Shock waves (traffic jams) form and propagate backwards. Click the road to create a jam.