An Efficient VBA Spreadsheet Algorithm and Model for the System Optimum Traffic Assignment

Introduction

In this paper, we consider the traffic assignment problem of assigning traffic to a transportation network. The objective is to minimize total system travel time, subject to satisfying the traffic demand between origin to destination pairs. The problem has traditionally been formulated as a nonlinear integer programming problem with a large number of decision variables and constraints, which makes it difficult to formulate and solve.

The main objective of this study is to propose a simplified two-phase method of formulating the problem and develop an algorithm using Microsoft Excel model with VBA code to solve the problem with much less effort. The secondary objective is to provide insights to practitioners to show how the Microsoft Excel with VBA could be successfully used in a transportation network model instead of complex mathematical optimization tools such as CPLEX (IBM, 2010) and LINDO (http://www.lindo.com/). For these purposes, we illustrated the efficiency of our approach using a simple Microsoft Excel example with VBA code.