1. Freeway Segments and Facility Chapters
HCM 6th Edition
Freeway Segments and Facility Chapters
Chapter 10, 12, 13, 14
March 2016
This presentation discusses the new material HCM Chapters 10 (Freeway Facilities), 12 (Basic Freeway Segments and Multilane Highway Segments), 13 (Freeway Weaving Segments), and 14 (Freeway Merge and Diverge Segments). The material on basic freeway and multilane highway segments has been combined into a new, single Chapter 12.
More detailed information on the actual computational procedures for this chapter are provided in Chapter 25 “Freeway Facilities Supplemental”, Chapter 26 “Freeway and Highway Segments Supplemental”, Chapter 27 “Freeway Weaving Supplemental”, and Chapter 28 “Freeway Merges and Diverges Supplemental”

2. PRESENTATION OVERVIEW
HCM 6th Edition: Chapter 10, 12, 13, and 14  overview and changes
FREEVAL-2015E Computational Engine: inputs, outputs, and interpretation
Illustrative examples
Discussion and wrap-up
This presentation gives an overview of the facility and segment chapters. Information about Chapter 11 (freeway reliability and ATDM) is given in a separate presentation.

3. NCHRP 3-115 project team and panel
Acknowledgment
NCHRP project team and panel
Members and friends of the TRB Committee on Highway Capacity and Quality of Service and its Freeway Subcommittee
TRB staff
This edition of the HCM was sponsored by NCHRP project The research team would like to acknowledge the support and feedback of the project panel as well as the active participation of members of the HCQS committee, with special thanks to the freeway and multilane subcommittee

4. Overview of Changes by Chapter

5. HCM2010 Major Update Freeway Chapters
Chapter 10: Freeway Facilities
Chapter 11: Freeway Reliability Analysis
Chapter 12: Basic Freeway and Multilane Highway Segments
Chapter 13: Freeway Weaving Segments
Chapter 14: Freeway Merge and Diverge Segments
Chapter 25: Freeway Facilities Supplemental
Chapter 26: Freeway and Highway Segments Supplemental
Chapter 27: Freeway Weaving Supplemental
Chapter 28: Freeway Merges and Diverges Supplemental

6. Why Analyze Freeways as Facilities?
Freeways needs to be analyzed as facilities as the traffic state in one segment influences other upstream and downstream freeway segments, and as congestion grows and dissipates over time as a function of changing demands and/or capacities. In the photo, the congestion at the top of the hill is starting to impact upstream operations (see brake lights), and over time will result in queuing in the basic freeway segment shown. The congestion is caused by a downstream bottleneck, and the basic segment in the photo may even have demand less than capacity.
Photo: Bastian Schroeder

7. Chapter 10: Freeway Facilities
A Look Ahead to the 2010 HCM
Chapter 10: Freeway Facilities
Method combines the analysis of multiple segments along an extended length of a freeway (up to 10-15mi)
Incorporates segment methodologies for basic, merges/diverges, and weaving segments
Considers oversaturated conditions with queue spillback
Consider operations over multiple (15 min) analysis periods
Main characteristics of the freeway FACILITY methodology are:
Combining the analysis of multiple segments along an extended length of the facility
Incorporating segment methodologies for basic, merge/diverge and weaving segments
Considering saturated and oversaturated conditions with ability to propagate queue to upstream segments
Performing the operations over multiple analysis periods 7
Kittelson & Associates, Inc.

8. Freeway Facility is Divided into Different Segment Types
Basic B segment (Ch. 11)
On-Ramp ONR segment (Ch. 13)
(1,500 ft, ~ 455 meters)
Off-Ramp OFR segment (Ch. 13)
Weaving W segment (Ch. 12)
Four different segment types are shown here.
Note that On- and Off-ramp segments have an influence area of 1,500 ft from to the gore area, respectively
The influence area on weaving segments is assumed to be 500 ft upstream and downstream from the gore area for each ramp
The segmentation into these segments needs to be done manually by the analyst, and guidance is provided in the chapter. Not shown is a special “overlapping ramp segment”, which occurs when an on-ramp is followed by an off-ramp within less than 3,000 feet, and if the two segments are not connected by an auxiliary lane (which would make it a weaving segment).

9. Chapter 10 - Freeway Facility Methodology
Revised presentation of method and computational steps (NCHRP )
Improved segmentation guidance for freeway facilities (NCHRP )
New generic speed-flow models (NCHRP )
New heavy vehicle impact estimation methods (NCFRP 41)
Integration of materials on manages lanes (NCHRP 3-96)
Integration of materials on work zones (NCHRP )
Planning methodology for freeway facilities (NCHRP 07-22)
New guidance for method calibration and validation (NCHRP )
Guidance for evaluating single-day ATDM strategy effects (FHWA Research)
Major changes/enhancements to Chapter 10, the freeway facility methodology, are listed here. In addition, the project these changes originated from are shown. Additional information is available in the respective final project reports.

10. Chapter 11 – Freeway Reliability Analysis
Standalone, new chapter in HCM2010 update
Updates the freeway travel time reliability materials from former Chap 36 & 37 in HCM2010 (SHRP-2, L08)
Description of the computational steps has been revised to more clearly present individual steps
Scenario generation process for freeway reliability analysis has been revised
Reduce number of scenarios and runtime
Improve modeling and using a Java Platform for computational engine
A standalone webinar will be offered to detail these changes!
Major changes/enhancements to Chapter 11, freeway reliability analysis, are listed here. In addition, the project these changes originated from are shown. Additional information is available in the respective final project reports.
Detailed information on Chapter 11 is provided in a separate presentation

11. Chapter 12: Basic Freeway and Multilane Highway Segments
Basic freeway segments and multilane highways merged into a single Chapter 12
One unified speed–flow equation for all basic and multilane highway segments (same equation form used also for managed lanes and truck adjustments)
New research is incorporated on truck effects on freeway operations, which has resulted in revised truck passenger car equivalent (PCE) tables and service volume tables.
Methods for evaluating basic managed lane segments is integrated into the chapter.
Added emphasis on calibration through capacity and speed adjustment factors (CAFs and SAFs).
Major changes/enhancements to Chapter 12, basic freeway and multilane highway segments, are listed here.

12. Chapter 12: Basic Freeway and Multilane Highway Segments
Driver population factor (fp) removed; effects of non-familiar drivers on flow is handled by CAFs and SAFs.
Density at capacity of multilane highway segments is revised to a constant density of 45 (pc/mi/ln).
The LOS E–F range for multilane highway segments is revised to reflect the revised density at capacity.
New speed–flow curves and capacities are provided for multilane highways for 65 and 70 mi/h free-flow speeds.
Major changes/enhancements to Chapter 12, basic freeway and multilane highway segments, are listed here.

13. Chapter 13 – Freeway Weaving Segments
Incorporates the methods for evaluating managed lane weaving segments, managed lane access segments, and cross-weave effects
Emphasis on calibration through the application of CAFs and SAFs
Chapter 27, Freeway Weaving: Supplemental, includes new example problems that illustrate the new methods
Major changes/enhancements to Chapter 13, freeway weaving segments, are listed here. The managed lane methodologies were developed under NCHRP

14. Chapter 14: Merge and Diverge Segments
Integrates method for evaluating managed lane merge and diverge segments
Provides new formalized guidance for aggregating merge and diverge segment densities for segments with three or more lanes
Chapter 28, Freeway Merges and Diverges: Supplemental, includes new example problems that illustrate the new methods
Major changes/enhancements to Chapter 14, merge and diverge segments, are listed here. The managed lane methodologies were developed under NCHRP

15. Details on Freeway Updates
The focus of this presentation is to highlight the changes and enhancements of the freeway facility methodology
Details on Freeway Updates

16. Chapter 10 - Freeway Facility Methodology
Revised presentation of method and computational steps (NCHRP )
Improved segmentation guidance for freeway facilities (NCHRP )
New generic speed-flow models (NCHRP )
New heavy vehicle impact estimation methods (NCFRP 41)
Integration of materials on manages lanes (NCHRP 3-96)
Integration of materials on work zones (NCHRP )
Planning methodology for freeway facilities (NCHRP 07-22)
New guidance for method calibration and validation (NCHRP )
Guidance for evaluating single-day ATDM strategy effects (FHWA Research)
First, we start with revised presentation of methods and computational steps. This work was performed under NCHRP project.

17. Improved—Detailed Methodology Presentation
HCM 2010 Methodology
HCM 6th Edition Methodology
Gray=Method
Computation
We see the HCM 2010 and the updated methodology side-by-side. As you see, the updated method has more steps. There is also a distinction between the computations or inputs that have to be done by the user and the computations that are performed by the software.
It is emphasized that the overall method did not change! What changed is the way the method is presented to make it (1) more transparent, (2) easier to follow by the user, and (3) consistent with the implementation in the computational engine or software.

18. Chapter 10 - Freeway Facility Methodology
Revised presentation of method and computational steps (NCHRP )
Improved segmentation guidance for freeway facilities (NCHRP )
New generic speed-flow models (NCHRP )
New heavy vehicle impact estimation methods (NCFRP 41)
Integration of materials on manages lanes (NCHRP 3-96)
Integration of materials on work zones (NCHRP )
Planning methodology for freeway facilities (NCHRP 07-22)
New guidance for method calibration and validation (NCHRP )
Guidance for evaluating single-day ATDM strategy effects (FHWA Research)
Let’s talk about the generic speed-flow model . . .
See paper:
Aghdashi S., N. M. Rouphail, A. Hajbabaie, and B. J. Schroeder. Generic Speed Flow Models for Basic Freeway Segments on General Purpose and Managed Lanes. Transportation Research Record: Journal of the Transportation Research Board, Vol. 2483, 2015, pp. 102 – 110.
Link:

19. New Generic Speed-Flow Model
𝑆= 𝐹𝐹𝑆 𝑎𝑑𝑗 𝑣 𝑝 ≤𝐵𝑃
𝑆= 𝐹𝐹𝑆 𝑎𝑑𝑗 − 𝐹𝐹𝑆 𝑎𝑑𝑗 − 𝑐 𝑎𝑑𝑗 𝐷 𝑐 𝑣 𝑝 −𝐵𝑃 𝑎 𝑐 𝑎𝑑𝑗 −𝐵𝑃 𝑎 𝐵𝑃 < 𝑣 𝑝 ≤ 𝑐
Eliminates the need to restrict FFS to 5 mph increments
Exact equation form applied to multilane segments
Form adjusted for managed lanes and truck effects
Free Flow Speed
Breakpoint
Now we have a single equation for allfree flow speeds. In other words, one equation represents the relationship between speed and flow, regardless of the free flow speed. As a result, increments of 5 mph for free flow speed are no longer required. This will streamline computations and facilitate application of the method in software. The equation also features build-in calibration factors in the form of capacity adjustment factors, and free-flow speed adjustment factors. These factors can be used to calibrate the bottleneck to match field observations, or can be used to represent non-recurring congestion effects from weather, incidents, or work zones.
Exhibit 12-7 Speed–Flow Curves for Basic Freeway Segments

20. Chapter 10 - Freeway Facility Methodology
Revised presentation of method and computational steps (NCHRP )
Improved segmentation guidance for freeway facilities (NCHRP )
New generic speed-flow models (NCHRP )
New heavy vehicle impact estimation methods (NCFRP 41)
Integration of materials on manages lanes (NCHRP 3-96)
Integration of materials on work zones (NCHRP )
Planning methodology for freeway facilities (NCHRP 07-22)
New guidance for method calibration and validation (NCHRP )
Guidance for evaluating single-day ATDM strategy effects (FHWA Research)
We do have a new methodology for heavy vehicles developed under NCFRP41

21. New Heavy Vehicle (HV) estimation method
Categorized into : Single-Unit Trucks (SUTs) Tractor-Trailers (TTs)
Two methodologies to assess the effect of HV
Traditional passenger-car-equivalent (PCE) factors to convert a mixed stream of cars and trucks to a single uniform PCE stream for purpose of analysis; when grades are light and truck % is low, and
A new mixed-flow model (MFM)that directly assesses the capacity, speed, and density of traffic streams that include a significant percentage of heavy vehicles operating on a single or composite grade.
MFM also must be used for mountainous terrain analysis
Exhibit Passenger Car Equivalents for General Terrain Segments
One key difference between HCM2010 and HCM 6th Edition is that there are now two types of trucks (SUT and TT), which were found to have very different effects on operations. Busses and recreational vehicles are lumped into the SUT category.
Another change is that there are two ways to asses HV effects. The PCE approach from HCM2010 and prior versions is retained and is the one most-frequently implemented in software and analysis tools. But the MFM method allows more detailed modeling of heavy vehicles and is considered more accurate for high heavy vehicle percentages or mountainous terrain.

22. Heavy Vehicle PCE’s
Specific Segment PCE values for a 30%/70% SUT/TT mix
Tables are available for a 50%/50% , 70%/30% mix
Interpolate for other mixtures
Extended tables to high % trucks
Equation also available
One big different is that rather than having one type of heavy vehicles, now we have a mix of single unit trucks and tractor trailers. We have tables that provide PCE values for a 30%/70%, 50%%/50% and 70%/30% mix. For other mixes values need to be interpolated. In addition, equations are available that can be used rather than using the table.
Exhibit PCEs for a Mix of 30% SUTs and 70% TTs

23. Heavy Vehicle Treatment in MFM
For combinations that include steep grades and/or high truck percentages the mixed flow model (MFM) described in Volume 4 is recommended for computing mix flow speeds and densities and auto and truck speeds in a mixed traffic stream
MFM uses
Adjustments to Generic Speed-Flow Equation
When a facility features steep grades and high truck percentages, using PCE values from the previous table is not recommended. Instead, the user needs to use mixed flow models that are described in Volume 4 for computing mix flow, auto, and truck speeds and densities.

24. Heavy Vehicle Treatment-MFM
Treat the traffic stream as combined
Under certain conditions, truck speeds affect the auto speeds
Estimate auto, truck speeds and densities separately
Uses a numerical simulation-based technique to estimate truck performance based on
Truck characteristics (Wt/HP ratio)
Grade %
Length of grade
Computational engine available to carry out the process
Here is how the mixed flow models should be used . . .

25. Chapter 10 - Freeway Facility Methodology
Revised presentation of method and computational steps (NCHRP )
Improved segmentation guidance for freeway facilities (NCHRP )
New generic speed-flow models (NCHRP )
New heavy vehicle impact estimation methods (NCFRP 41)
Integration of materials on manages lanes (NCHRP 3-96)
Integration of materials on work zones (NCHRP )
Planning methodology for freeway facilities (NCHRP 07-22)
New guidance for method calibration and validation (NCHRP )
Guidance for evaluating single-day ATDM strategy effects (FHWA Research)
See paper:
Aghdashi S., N. M. Rouphail, A. Hajbabaie, and B. J. Schroeder. Generic Speed Flow Models for Basic Freeway Segments on General Purpose and Managed Lanes. Transportation Research Record: Journal of the Transportation Research Board, Vol. 2483, 2015, pp. 102 – 110.
Link:

26. Integration of materials on managed lanes
Incorporated five basic managed lane segment types:
Five different managed lane segments are incorporated in the freeway facility methodology. The same generic speed flow modes with different parameters for each segment are developed. The speed flow models were originally developed in NCHRP Those models have been re-calibrated in NCHRP to have the same equation form as the generic equation shown earlier.
Continuous Access Buffer Buffer Barrier Barrier 2

27. Managed Lane Capacities
Managed lane capacities (or maximum observed flows) for different separation types
Exhibit Estimated Lane Capacities for Basic Managed Lane Segments
Managed lane capacities for different free flow speeds and separation (or segment) types are shown here. The term “capacity” is used loosely here, as many of these facilities did not actually break down (demand at these lanes is managed to avoid breakdown). As a result, these are better interpreted as maximum observed flows, suitable for planning purposes of managed lanes.

28. Managed Lanes – Speed Flow Curves Including the Effect of Adjacent GP Lanes Friction Effect
Adjusts the Generic Speed Flow Equation
Relationship depends of the type of separation
between GP and
Managed Lanes
As mentioned before, generic speed flow curves are used for managed lanes too. They incorporate the effect of adjacent lanes friction effects for different segment types. Each curve has a linear and curvilinear range in a two-regime model. The equation form is consistent with the generic equation, but with managed-lane specific parameters. The results are consistent with the original research in NCHRP 03-96, even though the equation form was modified in NCHRP for consistency.
Exhibit General Form for Speed–Flow Curves for Basic Managed Lane Segments on Freeways

29. Chapter 10 - Freeway Facility Methodology
Revised presentation of method and computational steps (NCHRP )
Improved segmentation guidance for freeway facilities (NCHRP )
New generic speed-flow models (NCHRP )
New heavy vehicle impact estimation methods (NCFRP 41)
Integration of materials on manages lanes (NCHRP 3-96)
Integration of materials on work zones (NCHRP )
Planning methodology for freeway facilities (NCHRP 07-22)
New guidance for method calibration and validation (NCHRP )
Guidance for evaluating single-day ATDM strategy effects (FHWA Research)
Freeway work zones are incorporated into the freeway facility methodology as well. Capacity and free flow speed models and adjustment factors are developed for different work zone types in NCHRP project. See the following paper:
Yoem. C., A. Hajbabaie, B. J. Schroeder, Vaughan C., X. Xuan, and N. M. Rouphail. Innovative Work Zone Capacity Models from Nationwide Field and Archival Sources. Transportation Research Record: journal of the Transportation Research Board. Vol. 2485, 2015, pp
Link:

30. Integration of materials on work zones
Model for (indirectly) estimating work zone capacity:
Observed QDR Capacity Adjustment  Work Zone Capacity
Model for estimating free flow speed in a work zones
The capacity of the work zone is observed indirectly. The reason is that in the field, only the queue discharge rate (QDR) can be measured reliably. The QDR is then adjusted by a capacity adjustment factor to identify work zone pre-breakdown capacity.
The QDR is predicted through a regression model developed under NCHRP That project also identified a relationship between QDR and pre-breakdown capacity. In addition, a model to estimate free-flow speed in work zones was developed. The models are shown in the following slides.

31. Observed Queue Discharge Rate model depends on:
Work Zone Capacity
Observed Queue Discharge Rate model depends on:
LCSI = Lane closure severity index (next slide)
fBr = Indicator variable for barrier type (concrete vs. cone, drum)
fAT = Indicator factor for area type (urban vs. rural)
fLAT = Lateral distance from the edge of travel lane adjacent to the work zone to the barrier, barricades, or cones (0–12 ft);
fDN = Indicator variable for daylight or night ( 0 for daylight)
Research showed that observed QDR depends on a number of factors as listed in this slide . More details on LCSI on following page

32. The Lane Closure Severity Index (LCSI)
𝐿𝐶𝑆𝐼= 1 𝑂𝑅× 𝑁 𝑜
OR = Open Ratio, the ratio of the number of open lanes during work zone to the total (or normal) number of lanes.
No = Number of open lanes in the work zone.
Exhibit Lane Closure Severity Index Values for Different Lane Closure Configurations
Lane closure severity index is an index to show the intensity of the lane closure. It is the inverse of open ratio times the number of open lanes. Open ratio is defined as the ratio of the number of open lanes during the work zone to the total number of lanes in non-work zone conditions.
LCSI accounts for the fact that a one-lane closure, has a more severe effect on a two-lane facility (LCSI=2), as opposed to a three-lane facility (LCSI = 0.75) or a four-lane facility (LCSI=0.44)

33. Work Zone QDR and FFS Models
Queue Discharge Rate Model (pc/hr/lane):
𝑄𝐷𝑅 𝑤𝑧 =2,093−154×𝐿𝐶𝑆𝐼−194× 𝑓 𝐵𝑟 −179× 𝑓 𝐴𝑇 +9× 𝑓 𝐿𝐴𝑇 −59× 𝑓 𝐷𝑁
Capacity is found by converting QDR to capacity (12%)
Free Flow Speed Model
𝐹𝐹𝑆 𝑤𝑧 = × 𝑓 𝑆𝑟 +0.53× 𝑆𝐿 𝑤𝑧 −5.60×𝐿𝐶𝑆𝐼−3.84× 𝑓 𝐵𝑟 −1.71× 𝑓 𝐷𝑁 −8.7×𝑇𝑅𝐷
Here you can see both QDR and FFS models. Both models are additive models and comparable with other HCM models. This models can used to find capacity and FFS adjustment factors to be incorporated in the Generic speed flow model. That’s how the effects of freeway work zones are modeled.
Notably absent from the models are lane width (the data set didn’t contain a large-enough variation), approach grade (same reason), and heavy vehicle percentages (research found that the “standard” PCE adjustment worked well for work zones … in other words, the truck effect in work zones is proportional to the truck effect in non-work zone conditions).
Ratio of non-WZ
To WZ Speed Limit
WZ Speed limit
Total Ramp Density

34. Chapter 10 - Freeway Facility Methodology
Revised presentation of method and computational steps (NCHRP )
Improved segmentation guidance for freeway facilities (NCHRP )
New generic speed-flow models (NCHRP )
New heavy vehicle impact estimation methods (NCFRP 41)
Integration of materials on manages lanes (NCHRP 3-96)
Integration of materials on work zones (NCHRP )
Planning methodology for freeway facilities (NCHRP 07-22)
New guidance for method calibration and validation (NCHRP )
Guidance for evaluating single-day ATDM strategy effects (FHWA Research)
We also developed a planning methodology for freeway facilities. See the following paper:
Hajbabaie A., N. M. Rouphail, B. J. Schroeder, and R Dowling. A Planning-Level Methodology for Freeway Facilities. Transportation Research Record: Journal of the Transportation Research Board, Vol. 2483, 2015, pp47-56.
Link:

35. Planning Level Methodology for Freeway Facilities
Reduce the analysis to Sections vs. HCM Segments
Sections are defined to occur between points where either demand or capacity changes
Example shows 7 sections, compared to up to 11 segments
A new planning-level method was developed under NCHRP to further simplify the evaluation of a freeway facility in a planning context. One major contribution of the planning level approach is to use the concept of sections rather than segments. A new section is defined when either the capacity or demand on the facility changes. Please see them on the graph. We do not have a merge or diverge section. They all are called ramp sections. The use of sections is also consistent with modern probe-based performance databases (e.g. INRIX, HERE, NPMRDS), which provide performance data from ramp gore point to gore point.

36. Planning Level Approach
Minimal inputs – info about the facility applicable to all analysis periods and sections
Free flow speed ( 𝑆 𝐹𝐹𝑆 )
Peak hour factor (𝑃𝐻𝐹)
Percent heavy vehicles (%𝐻𝑉)
General terrain type for truck PCE conversion
K-factor (converts directional AADT to peak hour flows)
Traffic growth factor (fg)
The planning level approach requires minimal amount of input. It is really a Back-of-the-Envelop approach. It can be easily used for an estimation on travel time, speed, queue length, etc.

37. Planning Level Approach
Five Computational steps
Step 1: Section Demand Calculations;
Step 2: Section Capacity Calculations and Adjustments;
Step 3: Delay Rate Estimation;
Step 4: Travel Time, Speed, and Density estimation ; and
Step 5: LOS (varies whether urban or rural)
Method will flag cases when analyst advised to use the more detailed operational analysis
Computational engine in Excel Platform available
It has five computational steps as shown here. The approach can also show sections where oversaturation occurs so that the analyst can focus on them in the future.

38. Chapter 10 - Freeway Facility Methodology
Revised presentation of method and computational steps (NCHRP )
Improved segmentation guidance for freeway facilities (NCHRP )
New generic speed-flow models (NCHRP )
New heavy vehicle impact estimation methods (NCFRP 41)
Integration of materials on manages lanes (NCHRP 3-96)
Integration of materials on work zones (NCHRP )
Planning methodology for freeway facilities (NCHRP 07-22)
New guidance for method calibration and validation (NCHRP )
Guidance for evaluating single-day ATDM strategy effects (FHWA Research)
There is also a new guidance on calibration and validation of the freeway methodology.

39. New guidance on calibration and validation
Calibration is performed sequentially at three levels
At the core freeway facility level (Chapter 10)
At the reliability analysis level, (Chapter 11) and
At the Active Traffic and Demand Management (ATDM) strategy assessment level (Chapter 11)
Calibration is performed sequentially at three levels as shown here . . .

40. New Guidance on Calibration and Validation:
Calibration at the core freeway facility level
Exhibit Calibration Steps for the Core Freeway Facility Level
We have a total of five steps for calibration at the core freeway facility level starting with gathering the input data, calibrate the free flow speed, bottleneck capacity, demand (as a last resort), and then validation

41. Calibration at the Reliability Level
Perform only after core facility calibration is done !
Predicted
Exhibit Comprehensive Reliability Calibration Steps
At the reliability level, the calibration methodology has five steps as shown here. For the examples that are shown, demand multipliers have to be calibrated as the predicted and observed curve different from the beginning. . . When the beginning are the same, incident probabilities and weather probabilities need calibration,
Observed

42. Calibration at the Reliability Strategy Assessment Level
Perform only after the Reliability calibration is done
Scenario-Specific calibration parameters are:
Speed adjustment factor,
Capacity adjustment factor,
Metering rate,
Demand adjustment factor,
Incident probability, and
Average incident duration.
Finally, for the ATDM, calibration is scenario-specific with the following parameters

43. FREEVAL COMPUTATIONAL ENGINE DEMO
Screen shot of FREEVAL . . .

44. Chapters 25 and 26 Illustration of Example Problems:
Six-lane Basic freeway LOS and capacity – The Facts:
Urban freeway segment
Volume = 5,000 veh/h (one direction, existing);
Traffic composition: 4% trucks
Rolling terrain;
Three lanes in each direction;
FFS = 70 mi/h (measured);
PHF = 0.96;
Commuter traffic (regular users);
Traffic growth = 5% per year; and
Facility operates under ideal conditions (no incidents, work zones, or weather special events).
Here are examples on the freeway methodology First we look at a simple basic freeway segment

45. Six-Lane Freeway LOS and Capacity
Step 1: Gather input data – Done!
Step 2: Estimate and adjust FFS – FFS is given!
Step 3: Estimate and adjust capacity (generic model !)
𝑐=2,200+10×( 𝐹𝐹𝑆 𝑎𝑑𝑗 −50)
𝑐=2,200+10× 70−50 =2,400 pc/h/ln
Step 4: Adjust demand volume
𝑣 𝑝 = 𝑉 𝑃𝐻𝐹×𝑁× 𝑓 𝐻𝑉
𝑓 𝐻𝑉 = 1 1+ 𝑃 𝑇 𝐸 𝑇 −1 = −1 =0.926
𝑣 𝑝 = 5, ×3×0.926 =1,875 pc/h/l

46. Six-Lane Freeway LOS and Capacity
Step 5: Estimate speed (generic speed/flow model) and density
𝐵 𝑃 𝑎𝑑𝑗 = 1,000+40× 75−𝐹𝐹 𝑆 𝑎𝑑𝑗 × 𝐶𝐴𝐹 2 =1,200 pc/h/ln
𝑆= 𝐹𝐹𝑆 𝑎𝑑𝑗 − 𝐹𝐹𝑆 𝑎𝑑𝑗 − 𝑐 𝑎𝑑𝑗 𝐷 𝑐 𝑣 𝑝 −𝐵𝑃 𝑎 𝑐 𝑎𝑑𝑗 −𝐵𝑃 𝑎
𝑆=70− 70− − − =64.7 mi/h
𝐷= 𝑣 𝑃 𝑆
𝐷= 1, =29.0 pc/mi/ln
Step 6: Determine LOS
From Exhibit 12-15, LOS is D

47. Evaluation of an Oversaturated Facility
Second, we look at a more complicated freeway facility analysis, which is performed using the computational engine

48. Evaluation of an Oversaturated Urban Freeway Facility
The Facts:
Single Unit Trucks and Buses = 1.25% (all movements);
Mainline Tractor Trailers = 1.00% (all movements);
Driver population  regular commuters;
FFS = 60 mi/h (all mainline segments);
Ramp FFS = 40 mi/h (all ramps);
Acceleration lane length = 500 ft (all ramps);
Deceleration lane length = 500 ft (all ramps);
Djam = 190 pc/mi/ln;
Ls = 1,640 ft (for Weaving Segment 6);
TRD = 1.0 ramp/mi;
Terrain = level;
Analysis duration = 75 min (divided into five 15-min time steps); and
Demand adjustment = +11% increase in demand volumes across all segments and time steps compared with Example Problem 1.
A queue discharge capacity drop of 7% is assumed.

49. Evaluation of an Oversaturated Facility
Step A3: Input Data
Traffic demand
Step A7: Compute segment capacities

50. Evaluation of an Oversaturated Facility
Step A10: Compute demand-to-capacity ratio
Step A12: Compute Segment Volume served and Speeds

51. Evaluation of an Oversaturated Facility
Step A12: Compute Density and d/C Based Segment LOS

52. Evaluation of an Oversaturated Facility
Step A15: Compute facility LOS by analysis period

53. Closing Thoughts

54. Capabilities of Freeway Facility Methodology
Enables the modeling of oversaturated & under-saturated conditions in an extended time-space domain ( 24 hrs. / 15 mi)
Models all active and highlights hidden mainline bottlenecks
Tracks queues as they form and dissipate across segments and time intervals
Allows time-variant demands and capacities
Models incidents and short term work zones
Validated against field data and compared to microsimulation very favorably
Here are the new capabilities of the freeway facility methodology 53

55. Limitations What the methodology ’s limitations are…
Does not account for off-ramp congestion due to surface street control and spillback onto mainline
Requires extensive demand inputs in each time period – cannot map sensor data to demand
Not reliable in reporting the effect of multiple overlapping queues (NCHRP 3-96a !)
Less reliable for the analysis extended length facilities (free-flow travel time greater than 15 minutes)
Time consuming in manually segmenting the facility into HCM analysis segments
Here are the limitations 54 55

56. Applications for Chapter 10
Chapter 10 method for freeway facilities can be a very powerful tool to evaluate freeway operations
Ability to run sensitivity analyses and various scenarios very quickly.
Computations are performed in a computational engine (FREEVAL) that is made available to HCM Users in Volume 4, including a Users Guide!
Limitations exist and need to be recognized
And finally applications for chapter 10 55

57. Discussion and Questions
Bastian Schroeder, Ph.D., P.E.
Principal Engineer
Kittelson and Associates, Inc.
(c)
(o) 57