Evaluation of design consistency on horizontal curves for two-lane state roads in terms of vehicle path radius and speed

Abstract

Experimental investigation was conducted on a 24 km long segment of the two-lane state road to collect the driver behavior data. The research involved 20 drivers driving their own cars equipped with the GPS device. Considering the impact of path radius and speed on the side friction demand, the design consistency on horizontal curves was evaluated by determining the margins of safety. The analysis showed that the vehicle path radii were mainly smaller than curve radius, on average for 12%. Regression analysis indicated that the percentage difference between the curve radius and vehicle path radius is not affected by the speed, speed differential and geometric characteristics of the curve and surrounding elements. Two different margins of safety were analyzed. One is the difference between maximum permissible side friction (based on design speed) and side friction demand, while another is the difference between side friction supply (based on operating speed) and side friction demand. Generally, demands exceeded supply side friction factors on curves with radii smaller than 150 m, whereas “poor” conditions (in terms of Lamm’s consistency levels) were noted for curves under approximately 220 m. Both values are very close to the critical radius below which higher accident rates were observed according to several accident studies. Based on the results of the research, it is proposed to use a 12% smaller curve radius for the evaluation of margin of safety and that curves with radii smaller than 200 m should be avoided on two-lane state roads outside the built-up area.

A systematic review on sensor-based driver behaviour studies: coherent taxonomy, motivations, challenges, recommendations, substantial analysis and future directions

“…The study that measured stopping behaviour at intersections is Hong et al (2016b), which measures how sensitive elder drivers are, in their approaching and stopping behaviour at intersections, when compared with younger drivers. Two studies provide initial results on the effect of speeding behaviour on different types of geometrical curves (Turner, Woolley & Cairney, 2015;Maljković & Cvitanić, 2016). One study uses the results of a small-scale NDS to evaluate the performance of existing models on two specific behaviours, car-following behaviour and curve behaviour (Fleming et al, 2019).…”

Dependence of Carriageway Crossfall on Operating Speed

“…Many guidelines [4][5][6], do not adequately define how to obtain a consistent road segment. Road segment consistency provides safe driving conditions at the desired speed across the route, whereas inconsistency is reflected when drivers need to slow down for a safe connection to the next road element, thus increasing the likelihood of an accident [7].…”