Photos of cars on freeway, speeding sign

Freeway Management and Operations Handbook

Back to Chapter 4 Page 2

Description of Figure 4-1: Estimated Frequency of Congestion, Volumes, and Speeds

This graph is labeled "Estimated Volume, Speed, and Reliability Conditions (2000)". It shows vehicles per lane per hour on the left vertical axis, ranging from 0 to 2,500 vehicles. Time of day is shown on the horizontal axis, ranging from 12 AM to 12 AM of the next day. Congestion frequency is shown on the right vertical axis, ranging from 0% to 100%. It is the basis volume by time-of-day graph, enhanced and expanded to also show the following:

  • The volume plot is shown as a curved line, color coded by average speed to show how this performance measure varies by time-of-day and by volume. It changes from green (12 AM) to yellow (5 AM) to red (5:30 AM to 9 AM) as volume increases and then changes back to yellow (9 AM) and then to green (3 PM).
  • Vertical bars show how frequently congestion (i.e., LOS F) occurs by time-of-day. Congestion occurs at least 70% of the time between the hours of 6 AM and 8 AM.