Abstract
This thesis documents the research comparing day and night vehicular speeds on horizontal curves on rural, two-lane highways. For each selected curve, daytime and nighttime operating speeds were measured using piezoelectric sensors. Speed data was collected in each direction at the midpoint of the approach tangent and at the midpoint of the curve. A vehicle's speed reduction was then calculated as the difference between the speed at the midpoint of the tangent and the speed at the midpoint of the curve. Hypothesis tests of daytime and nighttime speeds at the midpoint of the approach tangents resulted in the conclusion that a small percentage of curves exhibited a difference between daytime and nighttime speeds. However, no discernible pattern for the results could be found. Hypothesis tests of daytime and nighttime speeds at the midpoint of horizontal curves showed that over half the curves tested had daytime speeds that were significantly different from nighttime speeds. Even though a large percentage of statistically significant differences in mean speeds at the midpoint of curves were observed, no discernible pattern was evident. Statistical tests of the daytime and nighttime speed reduction from the approach tangent to the midpoint of the curve showed that five out of 16 curves had a significantly higher speed reduction at night than during the day. The results of this research indicate that there are some differences between daytime and nighttime speeds on rural, two-lane highways. However, because the magnitude of the difference between daytime and nighttime speeds is small for all degrees of curvature, a variable accounting for light condition is not needed for operating-speedbased profile modeling for horizontal alignment design consistency evaluation.
Guzman, Jesus (1996). Comparison of day and night vehicular speeds on horizontal curves on rural two-lane highways. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1996 -THESIS -G89.