A Framework for Efficient Dynamic Routing under Stochastically Varying Conditions

TL;DR

This paper presents a new stochastic routing framework that uses real-time ITS data and a Markov-modulated process to optimize vehicle routes under varying traffic conditions, improving travel time predictions.

Contribution

It introduces a novel stochastic process incorporating ITS information and develops the EDSGER* algorithm for real-time dynamic routing in complex networks.

Findings

EDSGER* algorithm effectively computes routes in real-time

The model captures both recurrent and non-recurrent congestion effects

Numerical tests show improved routing decisions using real data

Abstract

Despite measures to reduce congestion, occurrences of both recurrent and non-recurrent congestion cause large delays in road networks with important economic implications. Educated use of Intelligent Transportation Systems (ITS) can significantly reduce travel times. We focus on a dynamic stochastic shortest path problem: our objective is to minimize the expected travel time of a vehicle, assuming the vehicle may adapt the chosen route while driving. We introduce a new stochastic process that incorporates ITS information to model the uncertainties affecting congestion in road networks. A Markov-modulated background process tracks traffic events that affect the speed of travelers. The resulting continuous-time routing model allows for correlation between velocities on the arcs and incorporates both recurrent and non-recurrent congestion. Obtaining the optimal routing policy in the resulting semi-Markov decision process using dynamic programming is computationally intractable for realistic network sizes. To overcome this, we present the EDSGER* algorithm, a Dijkstra-like shortest path algorithm that can be used dynamically with real-time response. We develop additional speed-up techniques that reduce the size of the network model. We quantify the performance of the algorithms by providing numerical examples that use road network detector data for The Netherlands.