Analysis of Car-following Behavior on Sag and Curve Sections at Intercity Expressways with Driving Simulator

Yoshizawa, Ryuji; Shiomi, Yasuhiro; Uno, Nobuhiro; Iida, Katsuhiro; Yamaguchi, Masao

doi:10.1007/s13177-011-0043-z

Cited by 23 publications

(27 citation statements)

References 13 publications

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“…In general, the bottleneck is located 500 to 1000 m downstream of the bottom of the sag [3]. The factors reducing the capacity of sags seem to be related primarily to two changes in car-following behavior that occur when vehicles go through the vertical curve: i) drivers tend to reduce speed [1,3,4]; and ii) drivers tend to keep longer headways than expected given their speed [5,6,7]. These changes in car-following behavior seem to be unintentional [6].…”

Section: Causes Of Congestion At Sagsmentioning

confidence: 99%

“…The factors reducing the capacity of sags seem to be related primarily to two changes in car-following behavior that occur when vehicles go through the vertical curve: i) drivers tend to reduce speed [1,3,4]; and ii) drivers tend to keep longer headways than expected given their speed [5,6,7]. These changes in car-following behavior seem to be unintentional [6]. They are caused by a decrease in vehicle acceleration resulting from the combination of two factors: i) increase in resistance force; and ii) insufficient acceleration operation by drivers [1,6].…”

Section: Causes Of Congestion At Sagsmentioning

confidence: 99%

“…These changes in car-following behavior seem to be unintentional [6]. They are caused by a decrease in vehicle acceleration resulting from the combination of two factors: i) increase in resistance force; and ii) insufficient acceleration operation by drivers [1,6]. Drivers fail to accelerate sufficiently even though they generally perceive the increase in slope [4,6].…”

Section: Causes Of Congestion At Sagsmentioning

confidence: 99%

“…Consequently, sags often cause congestion in high traffic demand conditions [1]. The main reason why the freeway capacity decreases at sags is related to local changes in car-following behavior [3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

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Modeling Traffic at Sags

et al. 2014

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Freeway capacity decreases at sags due to local changes in car-following behavior. Consequently, sags are often bottlenecks in freeway networks. This article presents a microscopic traffic model that reproduces traffic flow dynamics at sags. The traffic model includes a new car-following model that takes into account the influence of freeway gradient on vehicle acceleration. The face-validity of the traffic model is tested by means of a simulation study. The study site is a sag of a Japanese freeway. The simulation results are compared to empirical traffic data presented in previous studies. We show that the model is capable of reproducing the key traffic phenomena that cause the formation of congestion at sags, including the lower capacity compared to normal sections, the location of the bottleneck around the end of the vertical curve, and the capacity drop induced by congestion. Furthermore, a sensitivity analysis indicates that the traffic model is robust enough to reproduce those phenomena even if some inputs are modified to some extent. The sensitivity analysis also shows what parameters need to be calibrated more accurately for real world applications of the model.

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Section: Causes Of Congestion At Sagsmentioning

confidence: 99%

Section: Causes Of Congestion At Sagsmentioning

confidence: 99%

Section: Causes Of Congestion At Sagsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Modeling Traffic at Sags

et al. 2014

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“…For example, in Japanese intercity freeways, 60% of traffic jams occur at sags [10]. The main cause of congestion appears to be that most drivers do not accelerate enough as they move along the vertical curve [11]. Consequently, they keep longer headways than expected given their speed [5].…”

Section: Introductionmentioning

confidence: 99%

Traffic Flow Optimisation at Sags by Controlling the Acceleration of Some Vehicles

Goñi-Ros

Knoop

Kitahama

et al. 2016

Traffic and Granular Flow '15

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Sags are bottlenecks in freeway networks. Nowadays, there is a growing interest in the development of traffic management measures for sags based on the use of in-car systems. This contribution determines the movements that individual (equipped) vehicles should make in order to minimise congestion. Specifically, we optimise the accelerations of some selected vehicles as they move along a one-lane freeway stretch with a sag, setting as objective the minimisation of total travel time. The optimisation results highlight the relevance of two traffic management strategies: a) motivating drivers to accelerate fast along sags; and b) limiting the inflow to sags. Also, they suggest ways to apply these strategies in practice by regulating the acceleration of vehicles equipped with in-car systems. These results prove the usefulness of the proposed method as a tool for control measure development.

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Coordination of horizontal and sag vertical curves on two-lane rural roads: Driving simulator study

Bella

2015

IATSS Research

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a b s t r a c t a r t i c l e i n f o Available online xxxxThe highway geometric design guidelines for several countries provide suggestions for the coordination of horizontal curves overlapping with sag vertical curves (sag combinations) to avoid combined configurations that produce undesirable optical effects and reduced safety. Such suggestions are derived from studies based on the drawing of the perspective of the road. This drawing method is severely limited with respect to the simulation of the perspective view of the highway to the driver during the dynamic task of driving. Interactive driving simulation methods are deemed to be more efficient for these objectives. This paper reports the results of a study carried out using an interactive driving simulator to evaluate the effects on the driver's speed behavior of different configurations of sag combinations and non-combined curves on a flat grade with the same features as the horizontal curves of the sag combinations (reference curves). The speed behaviors of drivers along the tangent-curve transitions of sag combinations and reference curves were recorded. The speed on the approach tangent, the speed at the midpoint of the horizontal curve and the maximum speed reduction (MSR), the difference between the maximum speed on the last 200 m of the approach tangent and the minimum speed on the first half of the horizontal curve, were analyzed. One-way repeated MANOVA was performed to determine if the driver's speed behavior on the horizontal curves was influenced by different configurations of sag combinations and reference curves. The primary result was that on suggested sag combinations, the driver's speed behavior did not differ in any statistically significant way from that on the reference curves. Whereas the critical sag combinations (configurations that should be avoided) caused high values of maximum speed reduction along the tangent-curve transition, which pointed to the driver's reaction to an incorrect perception of the road alignment. Therefore, this result confirmed the effectiveness of the road design guidelines for the coordination of horizontal curves and sag vertical curves.

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Analysis of Car-following Behavior on Sag and Curve Sections at Intercity Expressways with Driving Simulator

Cited by 23 publications

References 13 publications

Modeling Traffic at Sags

Modeling Traffic at Sags

Traffic Flow Optimisation at Sags by Controlling the Acceleration of Some Vehicles

Coordination of horizontal and sag vertical curves on two-lane rural roads: Driving simulator study

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