Transportation Statistics and Microsimulation

325

Appendix: Soft Modeling

and Nonparametric

Model Building

e models that have been discussed in this textbook, such as the normal

distribution and the straight-line regression, are very powerful tools in

transportation engineering. For example, using regression we can pre-

dict the eect of freeway trac given the trac on arterial roads. Using

normal distribution theory, we can predict the percentage of observations

that will fall with one, two, or three standard deviations of the mean.

Average speeds are oen reasonably modeled as normally distributed,

and trac congestion can oen be modeled as growing at a linear rate (at

least until capacit ...