CE 578 Highway Traffic Operations

1
CE 578 Highway Traffic Operations

• Introduction to Freeway Facilities Analysis

2
Objectives

• Process of freeway facility analysis
• Limitations of methodology

3
Bringing it All Together

• A freeway facility is comprised of different
  sections
• Each section is broken down into one or more
  segments and the steps to do this are
• Use the HCM methodologies

4
Bringing it All Together
5
Flow of Methodology
6
Time-Space Domain
7
Time-Space Domain

• Demand volume (d) (veh/hr)
• Capacity (c) (veh/hr)
• d/c ratio
• estimated speeds (S)
• estimated densities (D)
• LOS

8
Adjust Demand

• Input (observed or estimated)
• Traffic counts at entrances
• Traffic counts at exits
• Entrance volumes current demand volumes (Oi)
• Exit counts and demand volumes (Ej and Dj)
• Estimate exit demands
• Segment demand

9
Limitations

• Maximum length (9 to 12 miles)
• Flexible analysis period but 15 minute time
  intervals
• Vehicles leaving before or after the analysis
  period
• Complex occurrence of interactive bottlenecks
• Must adjust demands to consider effects of demand
  responsive
• Rerouting
• Mode choice
• Demand management

10
Limitations (cont.)

• Only local oversaturated flow
• First and last segments must be unsaturated for
  the duration of the analysis period
• All segments must be unsaturated at the beginning
  and ending time intervals of the analysis period
• Procedure not intended to implemented manually
• For heavy congestion may want to implement a
  simulation methodology