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From page 63... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 63 3. Analysis Methodology Development This chapter describes the development of the performance measure models recommended for use in the analysis methodology. Read the entire page →
From page 64... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 64 3.1.2. Passing Lane A passing lane segment, a relatively short length of roadway where an additional lane is provided in the same travel direction, is another mechanism for providing passing opportunities. Read the entire page →
From page 65... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 65 3.2. Estimation of Free-Flow Speed FFS values for various roadway and traffic conditions were obtained from non-linear regression analysis of the general speed-flow model presented in Equation (3-1) Read the entire page →
From page 66... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 66 slope coefficient is constant for this vertical class. Models fit to the vertical class 1 data showed that the BFFS, segment length, and opposing flow rate exerted little to no influence on the slope coefficient. Read the entire page →
From page 67... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 67 where FFSHCi = free-flow speed of horizontal curve subsegment i (mi/h) BFFSHCi = base free-flow speed of horizontal curve subsegment i (mi/h) Read the entire page →
From page 68... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 68 Tangent Segments Regression analysis was used to fit a model to the speed-flow slope coefficient data for tangent segments. Various linear and non-linear model forms were investigated and assessed based on accuracy and simplicity. Read the entire page →
From page 69... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 69 these equations differ by vertical class and segment type. Table 3-2, Table 3-4, and Table 3-6 present the coefficients for the passing zone/passing constrained segment models. Read the entire page →
From page 70... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 70 Table 3-4. Coefficients Used to Calculate b3 (Equation (3-7) Read the entire page →
From page 71... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 71 Horizontal Curves For horizontal curves, the slope coefficient is estimated with Equation (3-9) Read the entire page →
From page 72... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 72 equations differ by vertical class and segment type. Table 3-8 and Table 3-9 present the coefficients for the passing zone/passing constrained segment models. Read the entire page →
From page 73... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 73 3.4. Models for Estimation of Percent Followers The model development process for the estimation of percent followers largely followed that for the average speed models. Read the entire page →
From page 74... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 74 where b1–b7 = coefficient values, given in Table 3-11, and Other terms as defined previously. Table 3-11. Read the entire page →
From page 75... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 75 Table 3-13. Coefficient Values for Equation (3-15) Read the entire page →
From page 76... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 76 3.5. Passing Lanes Passing is an important operational phenomenon on two-lane, two-way, highways. Read the entire page →
From page 77... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 77 Where the effective length of passing lane is measured in miles, flow rate is measured in veh/h in the direction of analysis, and %NP represents the percent-no passing on the two-lane highway for several miles upstream of the passing lane segment in the direction of analysis. Read the entire page →
From page 78... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 78 Figure 3-2. Percent reduction in PF vs length of passing lane. Read the entire page →
From page 79... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 79 • Upgrade truck flow rate in excess of 20 veh/h. • One of the following conditions exists: o A 10 mi/h or greater speed reduction is expected for a typical heavy truck. Read the entire page →
From page 80... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 80 Figure 3-4. Upgrade speed versus distance curves for an intermediate semi-trailer truck Figure 3-5. Read the entire page →
From page 81... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 81 = 75 + × + × + × (3-20) where V = speed of heavy vehicle at the end of the upgrade segment (mi/h) Read the entire page →
From page 82... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 82 Table 3-19. Upgrade Speed Model Coefficients for an Interstate Semi-Trailer Truck. Read the entire page →
From page 83... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 83 Figure 3-6. Schematic of example 2+1 configuration (passing vehicles use center lane) Read the entire page →
From page 84... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 84 The following models were obtained to estimate the change in performance between a 2+1 configuration and a comparable two-lane highway with no passing lanes, approximately 50% passing zones, and 16-18 miles in length. Read the entire page →
From page 85... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 85 3.6. Level of Service The service measures, and corresponding level of service (LOS) Read the entire page →
From page 86... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 86 • Run the experimental design with the batch processing utility in HCM-CALC (Figure 3-8) for the HCM 2010 methodology. Read the entire page →
From page 87... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 87 follower density due to the lower speed. The LOS threshold values derived from this process are shown in Table 3-23. Read the entire page →
From page 88... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 88 = × (3-24) where FD = follower density in the analysis direction (followers/mi) Read the entire page →
From page 89... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 89 where FDF = average follower density for the facility in the analysis direction (followers/mi) , FDi = follower density for segment i in the analysis direction (followers/mi) Read the entire page →
From page 90... ... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 90 %% 1 100 100 1 100 Followers adj AvgSpeed %ImproveFollowersFollowerDensity FlowRate %Improve S  = × −    ×   × +    Eq. 28 where %Improve%Followers = % improvement to the % followers on a segment downstream of a passing lane segment, %ImproveAvgSpeed = % improvement to the average speed on a segment downstream of a passing lane segment, FollowerDensityadj = adjusted follower density on a segment downstream of a passing lane segment (followers/mi) Read the entire page →

From page 63...

... NCHRP 17-65 Improved Analysis of Two-Lane Highway Capacity and Operational Performance Final Report 63 3. Analysis Methodology Development This chapter describes the development of the performance measure models recommended for use in the analysis methodology.