Operating Speed Prediction Model as a Tool for Consistency Based Geometric Design of Four-Lane Divided Highways

Abstract

Researchers have studied two-lane rural highways to predict the operating speed on horizontal curves and correlated it with safety. However, the driving characteristics of four-lane-divided highways are different. Weak lane discipline is observed in these facilities, which influences vehicle speed in adjacent lane or space. So, irrespective of its lane or lateral position, vehicles in four-lane divided highways are considered free flowing only when it maintains the minimum threshold headway from any lead vehicle. Examination of two conditions is proposed to ensure the free flow. Vehicles meeting both conditions, when tracked from the preceding tangent section till the centre of the horizontal curve, are considered as free flowing. The speed data of such free flowing passenger cars at the centre of eighteen horizontal curves on four-lane divided highways is analysed to develop a linear operating speed prediction model. The developed model depends on curve radius and preceding tangent length. The operating speed of passenger car in four-lane divided highways is influenced by horizontal curve of radius 360 m or less. Further, longer tangent would yield higher operating speed at the centre of the curve. Finally, two nomograms are suggested for conventional design, consistency based design and geometric design consistency evaluation of four-lane divided horizontal curves.

Speed prediction models for car and sports utility vehicle at locations along four-lane median divided horizontal curves

“…It conforms to the result in literature [9]. However, the speed prediction models of passenger cars for the four-lane median divided highways available in literature [12][13][14][15] are applicable only at MC and have not considered the effect of speed in the preceding section. The proposed models can consider the speed in the preceding sections and predict the 85th percentile speed of car and SUV for the four-lane median divided highways at PC, MC, PT and PT50.…”

“…The proposed models can consider the speed in the preceding sections and predict the 85th percentile speed of car and SUV for the four-lane median divided highways at PC, MC, PT and PT50. Possibly, it helps in obtaining a model applicable at MC with higher adjusted R 2 value compared to some of the similar models available in the literature [12,15].…”

“…Nama et al [5] extensively studied the speed characteristics of passenger car and heavy commercial vehicle with weak lane discipline but did not provide a speed prediction model. On the other hand, Sil et al [15] developed the speed prediction model for passenger cars at MC only. Previous studies predominantly used regression analysis for model development [3,[15][16][17][18][19][20].…”

“…On the other hand, Sil et al [15] developed the speed prediction model for passenger cars at MC only. Previous studies predominantly used regression analysis for model development [3,[15][16][17][18][19][20]. Such analyses are easy to use and understand and have the ability to incorporate and analyze a large number of variables.…”

Modelos de velocidad de operación de carreteras rurales en terreno llano en Costa Rica

“…La mayoría de las metodologías de evaluación de la consistencia del trazado han desarrollado perfiles de velocidad o ecuaciones de pronósticos de este parámetro (Fitzpatrick et al, 2000;Sil et al, 2019).…”