Traffic and Public Transportation

These are papers from an earlier life. The most important papers from this era (actually, before I started my dissertation) were:

Powell, W.B. and Y. Sheffi, “The Convergence of Equilibrium Algorithms with Predetermined Step Sizes,” Transportation Science, Vol. 16, No. 1, pp. 45-55, (1982). (c) Informs

(Click here to download paper)

Sheffi, Y. and W.B. Powell, “An Algorithm for the Equilibrium Assignment Problem with Random Link times,” Networks, Vol. 12, No. 1, pp. 191-207, (1982).

These two papers were the first to discover the use of stochastic approximation procedures for solving complex traffic assignment problems. These papers applied a theory developed by Kiefer and Wolfowitz and Blum from the early 1950’s to solving stochastic optimization problems where the challenge was finding the stepsize. These papers “adapted” this theory, in a somewhat heuristic way, to the constrained optimization problem posed for modeling static traffic assignment problems.

(Click here to download paper)


  1. Sheffi, H. Mahmassani, W. B. Powell, “A Transportation Network Evacuation Model,” Transportation Research, Vol. 16A, No. 3, pp. 209-218, (1982).

This was one of the very earliest papers (and models) addressing the problem of evacuating people from around nuclear power plants. This model, called “Netvac1,” was written in the spring of 1980 for a local consulting firm, HMM Associates, in response to a new regulation requiring nuclear power plants to have an evacuation plan. The model used a deterministic, discrete-time simulation which kept careful track of intersection and lane capacities. As segments of the road would become full, cars would be prevented from moving forward. The model assumed that everyone was following a shortest path to a 10 mile radius, and this logic would adapt as road congestion changed. The model has taken on renewed interest following disasters such as Hurricane Katrina and the nuclear accident in Japan resulting from the tsunami.

(click here to download paper)

Sheffi, Y., H. Mahmassani, and W.B. Powell, “Evacuation Studies for Nuclear Power Plant Sites: A New Challenge for Transportation Engineers,” Journal of the Institute of Traffic Engineers, Vol. 51, No. 6, pp. 25-28, (1981).

Powell, W.B.,”A Stochastic Passenger Loading Model of Airline Schedule Performance,” Transportation Research, Vol. 17B, No. 5, pp. 399-410, (1983).

Powell, W. B., “Analysis of Airline Operating Strategies Under Stochastic Demand,” Transportation Research, Vol. 16B, No. 1, pp. 31-44, (1982).

Powell, W.B. and C. Winston, “A Numerical Investigation of the Impact of Uncertain Demand and Varying Risk Preferences on the Pricing and Capacity Decisions of Transportation Firms: the Case of Airlines,” Transportation Research, Vol. 17B, No. 6, pp. 471-490 (1983).

Powell, W.B. and Y. Sheffi, “A Probabilistic Model of Bus Route Performance,” Transportation Science, Vol. 17, No. 4, pp. 376-404, (1983). (c) Informs

Sheffi, Y. and W.B. Powell, “A Comparison of Stochastic and Deterministic Traffic Assignment Over Congested Networks,” Transportation Research, Vol. 15B, No. 1, pp. 53-64, (1980).