Selecting Ramp Design Speeds, Volume 2: Conduct of Research Report (2021) / Chapter Skim
Currently Skimming:
Pages 68-86
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 68... ...
68 Section 4. Development of Ramp Speed Prediction Models Based upon a review of the speed data collected as part of this project (see Section 3)
|
From page 69... ...
69 Table 18. Descriptive statistics of ramp speed database for curves Variable Descriptive Entrance Ramp Exit Ramp De pe nd en t V ar ia bl es Vehicle speed at midpoint of curve (VMC)
|
From page 70... ...
70 Entrance Ramps Several models were fit to predict vehicle speeds at the midpoint (MC)
|
From page 71... ...
71 Figure 15. Plot of actual versus predicted values of final model to estimate vehicle speed at midpoint of curve on an entrance ramp The final model to predict vehicle speeds at the end of curves on entrance ramps is provided as Equation 34.
|
From page 72... ...
72 Table 20. Statistical parameters of final model to estimate vehicle speed at end of curve on an entrance ramp Summary of Fit RSquare 0.943958 RSquare Adj 0.943818 Root Mean Square Error 1.835069 Mean of Response 47.25775 Observations (or Sum Wgts)
|
From page 73... ...
73 Figure 16. Plot of actual versus predicted values of final model to estimate vehicle speed at end of curve on an entrance ramp Exit Ramps Several models were fit to predict vehicle speeds at the midpoint (MC)
|
From page 74... ...
74 where: IDN = Indicator variable for downward slope (= 1 if the overall ramp slopes downward, 0 otherwise)
|
From page 75... ...
75 Figure 17. Plot of actual versus predicted values of final model to estimate vehicle speed at midpoint of curve on an exit ramp The final model to predict vehicle speeds at the end of curves on exit ramps is provided as Equation 36.
|
From page 76... ...
76 Table 22. Statistical parameters of final model to estimate vehicle speed at end of curve on an exit ramp Summary of Fit RSquare 0.95242 RSquare Adj 0.95201 Root Mean Square Error 2.55227 Mean of Response 43.54403 Observations (or Sum Wgts)
|
From page 77... ...
77 Figure 18. Plot of actual versus predicted values of final model to estimate vehicle speed at end of curve on an exit ramp 4.2 Ramp Speed Prediction Models for Tangents The objective of this statistical analysis was to develop ramp speed prediction models for tangents using an assembled database that included speed data from ramps located in Kansas, Missouri, and Texas.
|
From page 78... ...
78 Table 23. Number of tangents and observations in database to model speeds at the end of the tangent Entrance Ramps Exit Ramps Number of Tangents Number of Observations Number of Tangents Number of Observations Database used to model vehicle speed at end of Tangent with subsequent curve (Vt,e,c)
|
From page 79... ...
79 Table 24. Descriptive statistics of ramp speed database for tangents Variable Descriptive Entrance Exit D ep en de nt Va ria bl e Vehicle speed at end of tangent (VTan-End)
|
From page 80... ...
80 Table 25 provides a summary of the statistical results of the final model to predict vehicle speeds at the end of tangents followed by a subsequent curve on entrance ramps, and Figure 19 provides a plot of the actual to predicted values. VTan-End,C = 0.9667VTan-Begin + 143.9664LT – 5.3122I55 – 2.6028I60 – 7.9150I65 (37)
|
From page 81... ...
81 Table 25. Statistical parameters of final model to estimate vehicle speed at end of tangent with subsequent curve on an entrance ramp Summary of Fit RSquare 0.82122 RSquare Adj 0.82023 Root Mean Square Error 3.21828 Mean of Response 43.67047 Observations (or Sum Wgts)
|
From page 82... ...
82 Figure 19. Plot of actual versus predicted values of final model to estimate vehicle speed at end of tangent followed by subsequent curve on an entrance ramp The final model to predict vehicle speeds at the end of a tangent without a subsequent curve on entrance ramps is provided as Equation 38.
|
From page 83... ...
83 Table 26. Statistical parameters of final model to estimate vehicle speed at end of tangent without subsequent curve on an entrance ramp Summary of Fit RSquare 0.89381 RSquare Adj 0.89366 Root Mean Square Error 2.36062 Mean of Response 50.12304 Observations (or Sum Wgts)
|
From page 84... ...
84 Exit Ramps Several models were fit to predict vehicle speeds at the end of a tangent for tangents with subsequent curves and for tangents without subsequent curves on exit ramps. Only the best fitting models are provided here based on both statistical criterion (BIC)
|
From page 85... ...
85 Figure 21. Plot of actual versus predicted values of final model to estimate vehicle speed at end of tangent with subsequent curve on an exit ramp The final model to predict vehicle speeds at the end of a tangent without a subsequent curve on exit ramps is provided as Equation 40.
|
From page 86... ...
86 Table 28. Statistical parameters of final model to estimate vehicle speed at end of tangent without subsequent curve on an exit ramp Summary of Fit Root Mean Square Error 3.756292 Mean of Response 26.36756 Observations (or Sum Wgts)
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.