= Marginal external cost toll
{title2=$T_j(y)=yD_j\prime(y)$}
For a differentiable link delay $D_j(y)$, the toll $T_j(y)=yD_j'(y)$ charges a user for the additional delay imposed on the other users. Its perceived link cost is the derivative of $yD_j(y)$. The resulting <Beckmann potential> equals total travel delay. If total delay is <convex>, its <Wardrop equilibria> minimize that delay globally. Strict increase of $D_j$ alone does not imply this convexity; <optimal-flow calibrated congestion tolling> avoids that extra requirement.
Back to article page
