Transportation Statistics and Microsimulation

11

2Chapter

Graphical Methods

for Displaying Data

2.1 INTRODUCTION

As stated in Chapter 1, the objective of this textbook is to help transporta-

tion engineers—who are in practice, education, or research—learn basic

statistical techniques. e rst step in any engineering study should be a

graphical analysis, and in this text we use the term graphical liberally. For

example, consider the map of current speeds from the city of Houston’s

trac management center, TRANSTAR, shown in Figure 2.1.

On this map, the darker the freeway link is shaded, the more severe the

congestion is on that link. e darkest shaded links indicate a speed of less

than 20 ...