Abstract
This thesis documents efforts to validate two elements related to an operating-speed-based geometric design consistency evaluation procedure: (1) the speed reduction estimation ability of the model, and (2) assumptions about acceleration and deceleration behavior of drivers approaching and departing horizontal curves. Detailed data collection and analysis procedures used to analyze operating speeds, acceleration and deceleration on curves and their tangents are presented. Hypothesis tests of mean observed and estimated speed reductions resulted in the conclusion that, for curves with no downstream intersections, the mean observed reduction in operating speed is not statistically different from the estimated mean reduction in operating speed at a 0.05 significance level. Analysis of observed 85th percentile speeds revealed that the current speed-profile model fits the observed data reasonably well. Hypothesis tests of mean observed 85th percentile speeds on tangents resulted in the conclusion that the mean observed 85th percentile speed on tangents is not statistically different from the assumed desired speed on tangents (97.9 km/h) at a 0.05 significance level. Inspection of implied acceleration and deceleration rates revealed that adjustments in acceleration and deceleration take place throughout an alignment, especially in and near curves. Tests of mean acceleration and deceleration rates indicate that the assumption of equal acceleration and deceleration rates at 0.85 M/S2 is reasonable for the purposes of this model. Further research is needed to confirm this conclusion. The results of this thesis support the continued use of the model until further research is conducted to enhance the model
Collins, Kent Michael (1995). Validation of and enhancements to an operating-speed-based geometric design consistency evaluation model. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1995 -THESIS -C654.