1 / 21

CE 578 Highway Traffic Operations

CE 578 Highway Traffic Operations. Lecture 4: HCM Directional Analysis. Objectives. Understand two-lane highway performance measures Relate two-lane highway conditions to input variables Calculate adjusted volume Calculate performance measures ATS PTSF.

Download Presentation

CE 578 Highway Traffic Operations

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. CE 578 Highway Traffic Operations Lecture 4: HCM Directional Analysis

  2. Objectives • Understand two-lane highway performance measures • Relate two-lane highway conditions to input variables • Calculate adjusted volume • Calculate performance measures • ATS • PTSF

  3. Two-Lane Highway Performance Measures • Percent-time-spent-following (PTSF) • Average travel speed (ATS) • Average travel time • Passing supply vs passing demand

  4. HCM Procedure (Chapter 12) • Precept—Mobility • Consistent high speed • Infrequent passing delays • Precept—Access • Infrequent passing delays • Freedom to maneuver • Safety • Speed not a primary concern

  5. HCM Procedure Two-Lane Highway Classes • Different highways and different expectations • Primary arterials: serve long distance trips, major inter-city travel, daily commuter routes, high travel speed expected • Secondary roadways: high speed not expected, scenic route, rugged terrain, recreational route, short trips, trip ends

  6. Level of Service Measurement by Highway Classification • Class I: PTSF and ATS • Passing delay is expected to be at a minimum • High speed is expected • Class II: PTSF • Higher levels are acceptable but drivers are still sensitive to this measure • ATS is generally not an issue • Drivers will not be on the highway long • Or do not expect high speeds

  7. Estimating Two-Lane Highway Level of Service Measures • Microscopic simulation • TRAR • TWOPAS • Yu and Washburn • Deterministic procedures • US HCM two-way methodology (not necessary) • US HCM directional methodology • Polus

  8. US HCM Procedures—General Approach Input Highway Conditions Adjustments and Calculations Compute Performance Measure(s)

  9. US HCM Performance Measures—Base Conditions • 12 ft lanes • 6 ft shoulders • No no-passing zones • 100% passenger cars • No impediments to through traffic • Level terrain • 50/50 traffic split by direction

  10. Base Condition PTSF Estimation: Graph (50/50 directional split)

  11. US HCM Level-of-Service—Class I Facilities

  12. US HCM Level-of-Service—Class II Facilities

  13. Original HCM Directional Analysis Procedure • Relative to two-way analysis procedure • Split traffic by direction • Analyze each direction of traffic separately • Volume adjustments are the same for general terrain • ATS • Equation 20-15 • adjustments (use 20-19) • PTSF • Coefficients for BPTSF (use 20-21) • Equations 20-16 and 20-17 • adjustments (use 20-20) (take care to use analysis direction flow and opposing flow, not two-way flow)

  14. Modified HCM Directional Analysis Procedure • No change in volume adjustments • No change in ATS calculation • PTSF calculation • Same BPTSF equation • New PTSF equation • New BPTSF coefficients • See Table 9 (handout) • New adjustments  replacing fnp • See Table 10 (handout)

  15. Exercise—Estimating Performance Measures • Given (Ideal Conditions): • Terrain = level • % Trucks = 0.0% • % RVs = 0.0% • class I highway with base conditions, • PHF = 0.85 • vd= 750 pcph, • vo = 450 pcph, • no no-passing zones, • FFS of 60 mph • 60/40 directional split • Find • ATSd • PTSFd and • LOS

  16. Application • Given • Class I • V = 600 vph • Terrain = Rolling • 60/40 split • 60% no-passing zones • PHF = 0.90 • 10% Trucks 5% RVs • FFS = 65 mph

  17. Combining Directional Performance Measures • ATS • See HCM 2000 Chapter 20 pp 20-12 and 20-29

  18. Combining Directional Performance Measures (cont.) • PTSF • See HCM 2000 Chapter 20 pp 20-12 and 20-29

  19. Things to Note from Assignment 5 • How to combine directional performance estimates into a two-way estimate • How to perform an iteration to maintain consistency between the factors and the adjusted volumes. • Limitations of HCM methodologies (stay tuned)

  20. Review Assignment 3 • See website for the problems and solutions

  21. Limitations • Sensitivity to highway section length • Intersection operations • Capacity conditions

More Related