• International Journal of Highway Engineering
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• v.10 no.2
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• pp.125-133
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• 2008

Achieving consistent geometric design is an important goal in highway design to ensure obtaining safe, economical and smooth traffic operation. Most evaluation of consistency is based on 'speed change' in speed profile. According to literature, the speed depends on geometric elements, speed on tangent section prior to a curve, and background around roads. Especially, the radius is the most main element mentioned in various literature. Therefore, this paper shows two ways of calculating horizontal radius on real road, that is, three-dimensional road. First of all, the radius of horizontal curve is calculated based on physical method. The calculated radius contains not only superelevation but also longitudinal grade while the current minimum radius is calculated by considering superelevation and side friction according to the point-mass equation. Secondly, the problem of composed curves with distorted appearance by overlaying sag or crest vertical alignment has been known. To quantify the extent of distortion effects, the method of calculation of real seen so called 'Perspective Radius' is developed. The paper presents the perspective radius and recommended perspective radius.

• Journal of Korean Society of Transportation
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• v.19 no.2
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• pp.21-28
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• 2001

This study is to estimate the through car equivalent for left-turn movement according to left turn radius in the signalized intersection. The saturation flow rate for left-turn movement in 92' KHCM(Korea Highway Capacity Manual) is the same as that for through movement in the signalized intersection where the left turn radius is over 20m. This study uses Duncan 'Test's Test in order to find out the saturated position for queued vehicle in the signalized intersection. It found that the saturated flow rate of left-turn movement in the signalized intersection is less than that of through movement where the left-turn radius is less than 20m. It found that the through car equivalents for left-turn movement according to left-turn radius(8m-20m) are between 1.05 and 1.14.

• Proceedings of the KOR-KST Conference
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• 1999.10a
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• pp.315-320
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• 1999

교차로 좌회전 이동류에 대해 곡선반경의 확보여부는 용량 및 안전성측면에 많은 영향을 주게 된다. 죄회전 곡선반경의 결정은 설계기준차량의 회전궤적에 따라 결정되며 곡선반경의 모양은 원곡선의 형태를 유지하는 것이 바람직한 형태로 제시되고 있다. 교차로 설게시 곡선반경의 확보방안으로 정지선을 후퇴시키는 방안을 제시함으로서 좌회전 이동류에 대해 용량 및 안전성을 개선할 수 있도록 하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6D
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• pp.663-673
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• 2009

Driver's perceived curve radius is different from actual curve radius at curve sections. This is called visual distortion. It has effect on operation speed according to driver's perception and finally bad effect on safety at curve sections. At present, however, there is no research on quantitatively analysis of visual distortion and no criteria for curve section design considering the visual distortion. Therefore, this study focus on finding degree of visual distortion and suggesting design criteria by visual distortion analysis. The process of this study is as below; First, a calculaiton model of perceived curve radius was developed by survey using computer simulation. In this model, a dependent variable is perceived curve radius and an independent variable is geometric factors. Second, degree of visual distortion was calculated from ratio of perceived curve radius to actual curve radius. Finally, design criteria were suggested through influencing factor analysis of visual distortion at curve sections.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4D
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• pp.395-402
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• 2010

The seriousness of a traffic accident appears relatively higher on the curve sections compared with the straight sections due to a change in speed caused by a change in the driver's sight. In particular, the visual distortion phenomenon, one of the dangerous factors taking place on the curve sections, appears different according to the road's geometric design. Although it is a genuinely principal design factor which should be necessarily considered in designing a road, the previous researches on establishing the design standards for it have been insufficiently conducted. As a result, the establishment of the road design standards for the curve sections considering the sight distortion phenomenon is desperately required. This research examined the previous researches on the driver's behaviors, the driver's sight characteristics and the perceived curve radius on the curve sections, and developed the theoretical model of perceived curve radius to which a mathematical technique is applied in consideration of the visual distortion phenomenon on the two-lane curve sections in a local area. In addition, after the theoretical visual distortion was calculated on the basis of the theoretical model of perceived curve radius, the range of error on the theoretical recognition radius model formula was verified through comparing it with the previous researches' experiential visual distortion level and analyzing both of them. As a result, it was observed that as the curve radius practically increases in the theoretical recognition curve radius, the range of error tends to go down, which reflects well the characteristics of the curve sections on the road. Based on this research, it is expected that this research will be helpful to eliminate the safety defects when designing the curve sections and contribute to develop the road design standards considering human factors in the future.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.4
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• pp.34-43
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• 2012

The behaviors of the curved bridges which has been constructed in the RAMP or Interchange are very complicate and different than orthogonal bridges according to the variations of radius of curvature, skew angle and spacing of shoes. Occasionally, the camber of girder and negative reactions can be occurred due to bending and torsional moment. In this study, the effects on the negative reaction in the curved bridge were investigated on the basis of design variables such as radius of curvature, skew angle, and spacing of shoes. For this study, the twin-steel box girder curved bridge with single span which is applicable for the RAMP bridges with span length(L) of 50.0m and width of 9.0m was chosen and the structural analysis to calculate the reactions was conducted using 3-dimensional equivalent grillage system. The value of negative reaction in curved bridges depends on the plan structures of bridges, the formations of structural systems, and the boundary conditions of bearing, so, radius of curvature, skew angle, and spacing of shoes among of design variables were chosen as the parameter and the load combination according to the design standard were considered. According to the results of numerical analysis, the negative reaction in curved bridge increased with an decrease of radius of curvature, skew angle, and spacing of shoes, respectively. Also, in case of skew angle of $60^{\circ}$ the negative reaction has been always occurred without regard to ${\theta}/B$, and in case of skew angle of $75^{\circ}$ the negative reaction hasn't been occurred in ${\theta}/B$ below 0.27 with the radius of curvature of 180m and in ${\theta}/B$ below 0.32 with the radius of curvature of 250m, and in case of skew angle of $90^{\circ}$ the negative reaction hasn't been occurred in the radius of curvature over 180m and in ${\theta}/B$ below 0.38 with the radius of curvature of 130m, The results from this study indicated that occurrence of negative reaction was related to design variables such as radius of curvature, skew angle, and spacing of shoes, and the problems with the stability including negative reaction will be expected to be solved as taken into consideration of the proper combinations of design variables in design of curved bridge.

• Journal of Korean Society of Transportation
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• v.20 no.7
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• pp.95-105
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• 2002

Under a specific roadway alignment condition by design-speed standards, safety of the roadway is determined by an actual operating speed of a driver. This research takes first lanes of four-lane(hi-direction) rural highways as target facility. It also takes the straight and curved lanes of the selected highways for in-depth study. This study used NC-97 to detect speeds of passenger cars whose speeds are not affected by front vehicles. This research analyzed properties of 85th percentile operating speed at upstream of horizontal and through curves under various alignment conditions. The results show that 53∼65 Percent of drivers drive faster than the posted speed-limit (80KPH) by 14∼20 KPH on average. It also shows that the 85th-percentile operating speeds are the lowest at the middle point of curve length when curve radius is smaller. However, they are lowest at 1/4 point of curve length when curve radius is greater. Along roadways where curve radius is small, difference between upstream speed and the speed along the curve is considerably large. On the other hand. the speed difference is setting smaller as the curve radius is increasing. According to the results, significant variables affecting the 85th percentile operating speeds are curve radius and the 85th-Percentile operating speeds of upstream curves.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.10
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• pp.26-32
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• 2019

The purpose of this study is to improve the running speed on a small-radius curved section on an existing train line. When the transition curve was extended, and the amount of movement in the horizontal direction tended to increase as the curve radius increased. The amount of increase in the transition curve extension was lowest when extending the curve radius, and the amount of horizontal movement was the lowest when changing the curve radius to a cosinusoidal curve. As a result of applying the pass rate after improvement to the Kyeongbu line, there was a time-shortening effect of 9.4 to 11.6% and a facial expression speed increasing effect when the curve radius was fixed and the transition curve was changed to a sinusoidal curve. In conclusion, the most effective way to improve the running speed on an existing train route is to change the image to concrete and to change the relaxation curve to a cosinusoidal curve. The amount of horizontal movement of the track is small, and the speed improvement effect is excellent.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6A
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• pp.955-963
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• 2006

As the geometrical characteristic of the curved bridge, the seismic response of curved bridges are different from straight bridges. This study analyzed the seismic response of the curved bridges considering diverse factors such as radius of curvature, direction of seismic load and support condition. The improved simple modeling of the curved bridge for seismic analysis is proposed, and it is compared with the detail modeling in order to verify the simple modeling. Three simply supported curved bridges and six 3-span continuous bridges are selected for seismic analysis. The behavior of curved bridges are evaluated in terms of the displacement and the force at supports and piers under seismic load applied in various directions. The results of this study show that upward reaction force may appear in simply supported curved bridge under seismic load. And continuous curved bridges are affected by the direction of the seismic load.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.10
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• pp.345-353
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• 2020

On conventional railway lines, trains with different speeds are operated. Therefore, trains moving on curved sections with cants must accept various ranges of balanced cants, cant deficiency, and cant excess, which is essential for the comfort and safety of train operation. In this study, the correlation between the curve radius, cant, and train speed on a track was analyzed to check the cant range that satisfies the criteria of train types, operation speed, cant deficiency, and cant excess. Also, the range of setting the cant by the curve radius and balanced cant were calculated by a regression analysis of train speed according to the frequency of operation in the case of mixed trains. The results could make it possible to improve the speed of the operation route, reduce the loss of ride quality, reduce the risk of derailing caused by cant deficiency, and minimize the load deflection by excess cant. This will ensure the safety of trains running on curves and improve the efficiency of track maintenance.