Probability Density Function (PDF): Plots of several hypothetical normal distributions with various means (µ) and variance (σ2). For transportation applications, horizontal axis could represent various travel times while vertical axis could represent the probability of their occurrence.

Cumulative Distribution Function (CDF): The CDF is a plot of the same data as the PDF. Curves with the same colors represent the corresponding PDF plot. These curves indicate the probability that the travel time will be less than or equal to the value on the X axis.

*Use 50th percentile travel time for calculating TTI

Source: 2013 Maryland Mobility Report

For inquiries regarding the ITS PCB Program, please contact the USDOT Point of Contact below. J.D. Schneeberger Program Manager, Knowledge and Technology Transfer John.Schneeberger@dot.gov