• International Journal of Highway Engineering
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• v.16 no.5
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• pp.165-171
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• 2014

PURPOSES : The objective of this study is to find Percentile Speed($V_p$) for Appraisal of Road Section with Recurring Congestion. METHODS : Percentile Speed($V_p$) is determined by correlation analysis of CSI that proposed existing literature. and CSI(Consistency Service Index) is a index that subtract service fail frequency from 100 points, and service fail is defined as traffic situation is driving less than 80kph speed. In this study, We analyzed the highest correlation percentile speed associated with CSI. This speed is chosen as a delay decision speed. In order to verifying reliability, it performed a comparison with the previous method. RESULTS : As a result, 30 percentile speed($V_{30}$) was decided as index speed for judgement of recurring congestion section, and through comparison with existing methods, we demonstrated that 30 percentile speed can be useful for judgement of recurring congestion section. CONCLUSIONS : This method to Determine recurring congestion section using the percentile speed($V_{30}$) was proposed for the first time in this paper. This method can be applicated more quickly and easily than existing method for determining of recurring delay section.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2D
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• pp.105-111
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• 2010

Operating speed is one of key elements in the design and operation of freeway. Few studies have been carried out macroscopically to find characteristics of free-flow speed (FFS) using small sample size and not considering the conditions of traffic volume and the effects of hour periods. As an attempt to find out the characteristics of FFS, this study microscopically analysed both the distributions of freeway FFS and percentile speeds according to traffic volume and daily hour periods using huge sample size. It was found out that speed distributions are changed and showed different behaviors under the conditions of traffic volumes(1-5 veh/30sec) and daily hour periods(0-5, 6-8, 9-11, 12-19, 20-23). V85(85th percentile speed) at morning, night, and midnight period decreases according to increase in traffic volume respectively, whereas V85 at day time does not show considerable differences. So the behaviors of V85 according to hour periods dramatically changed according to the increase in traffic volume.

• International Journal of Highway Engineering
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• v.9 no.3
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• pp.83-89
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• 2007

When allocating traffic signal at the signalized intersection, minimum green time and clearance time for bicyclists should be significantly considered in order to enhance safety aspects to bicyclists when crossing intersections, especially where intersections with exclusive bicycle paths that are physically separated from pedestrians. In this study, field measurements related to bicycle crossing time, including minimum peen time and clearance time, were collected and analyzed according to bicycles crossing types at the signalized intersections where high rate of bicyclists exists. Three types of bicycle crossing are defined as follows 1) stopping: completely stop before crossing (at least one foot on found) 2) riding: crossing with riding bicycle 3) pulling: crossing without riding bicycles. Minimum green time based on pedestrian speeds should be used as crossing time in this case. For bicyclists, speed of bicycle that is applicable to estimate the minimum green time is in the 1.36m/sec($15^{th}$ percentile) to 1.60m/sec($25^{th}$ percentile) range in case of its stopping. Also it is in the 0.75($15^{th}$ percentile) to 0.87($25^{th}$ percentile) range for pulling at crosswalk. In addition, speed of bicycle to consider for calculating the clearance time is in the 2.51m/sec($15^{th}$ percentile) to 2.79m/sec($25^{th}$ percentile). These values also resulted from $15^{th}$ percentile or $25^{th}$ percentile speeds of riding. The results of this study are expected to be supported in traffic signal allocation process, reflecting bicyclists' characteristics.

• Journal of the Korean Society of Safety
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• v.21 no.3 s.75
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• pp.107-113
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• 2006

Speeding is one of major causes of frequent and severe traffic accidents in school zones. In this paper, the long-term effectiveness of speed monitoring displays (SMD) on speed variability was investigated through a field study in a school zone environment. The performance difference was discussed with several dependent variables including average speed, 85th percentile speed, and distribution of speed. Study results showed that the speed of vehicles began to reduce where the driver recognized the presence of an SMD, and about 12.4 percent (5.8km/h) of average speed was reduced at the SMD location. This speed reduction was observed throughout the day regardless of time of day. Statistical tests showed that the speed difference was statistically significant. In addition, analysis results of speed distribution showed that the number of speeding vehicle was greatly reduced after the SMD was installed, and 85th percentile speed also decreased from 54.3km1h to 45.0km/h. Therefore, it was concluded that the application of SMD produced a positive impact on the driver's behavior for a long period of times.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.19 no.4
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• pp.45-54
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• 2020

This study investigated basic data on walking characteristics, including walking speed and cognitive-response for the elderly, and based on these, the time of walking signal was calculated. The on-site survey examined the actual pedestrian crossing speed using a stopwatch, and the age was divided into groups of ordinary people and the elderly. Analysis of the data showed that the average walking speed for the general public was 1.29 m/s, while the average walking speed for the elderly was 1.13 m/s, higher than that of the general public. In addition, the lower speed of the 15th percentile was analyzed to 1.01 m/s for the general population and 0.85 m/s for the elderly, showing a lower walking speed than the standard for the general area and 0.8 m/s for the protected area. However, for senior citizens who use walking sticks or wheelchairs, the speed of the lower 15th-percentile is 0.73 m/s, which is lower than the current standard of protected areas, according to the analysis.

• 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.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2004.11a
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• pp.233-238
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• 2004

In this study, speed survey has been conducted on Pusan Freeway to identify actual running speed. therefore, suggest that Highway Design Regulations and Highway Design Standard from Ministry of Construction and Transportation, which requires stopping sight distance for 20% less speed when rainy condition in accordance with Highway Safety Act, is not coincident with driver's characteristics. Consequently, it is prudent to compute stopping sight distance with 85th percentile running speed, considering driver's actual behavior and mountainous terrain.

• Journal of Korean Society of Transportation
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• v.25 no.4
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• pp.7-19
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• 2007

The purpose of posted speeds is to provide a speed that ensures the safety of vehicle flow according to given road situations. Because of this, posted speeds must be carefully examined, and posted speeds at freeway exits and entrances in particular should consider car characteristics. Posted speeds at freeway exits and entrances must take changing speeds due to curve radiuses into consideration and in this study, an 85th percentile speed becomes the most important element to consider. When it is considered that most traffic accidents occur because of variations in speed between cars, posted speeds should be set after considering car traveling characteristics. Within these dimensions, instead of putting significance on an upper direction regulation or lower direction regulation, speed distributions which fit to the characteristics of each road should be fully considered. Accordingly, this study evaluated appropriate posted speeds that will reduce the dangers of traffic accidents through posted speed regulations of roads now in operation by offering a posted speed setting method theory, using entries at Yangji, Yongin, and Cheongwon interchanges as subjects.

• Journal of Korean Society of Transportation
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• v.12 no.2
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• pp.47-63
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• 1994

The purposes of this study are to identify Traffic Flow characteristics and to develop approach delay model of unsignalized intersection based on the travel speed in the conflicting area. The results of this study are as following ; 1. The cumulative frequency distributions of Left-turning speed show a few differences among approaches and they are distributed to lower range of speeds. On the other hand, those of through speed show obvious differences among bounds. The similar results also show in the analysis of Percentile speed. 2. The effectiveness of conflicting movements to travel speed in the conflicting area are analyzed using regression analysis. Left-turning speed model shows that Left-and Right-Conflicting speed. Through-speed model is also developed, when approaching through volume is less than 420vph. 3. Since the lost time due to the acceleration stop, and decelerlation is occured in the conflicting area, approach delay model is delivered using the travel speed models under the condition of small queuing delay.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.21 no.5
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• pp.149-161
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• 2022

Because the speed limit affects moving speed, it is closely related to traffic accidents as well as traffic flow. The existing speed limit calculation methods consider various engineering factors such as lanes, intersection spacing, driveways, crosswalks, 85 percentile speed, land uses, and roadway geometric characteristics etc. However, it can be said that the engineering analysis is insufficient because the traffic impact analysis considering traffic volume is not carried out. In addition, only 85 percentile speed, which is the spot speed, does not reflect the characteristics of the traffic flow on the road. In this paper, the effect of the speed limit change on the moving speed and the travel speed was analyzed in detail accordinr to the variation of intersection spacing and traffic volume. And by using the results, we proposed a speed limit calculation method that maintains the same service level as before the speed limit change, thereby increasing the speed improvement effect and reducing the difference between moving speed and travel speed. In addition, a variable speed limit operation method according to the change in traffic volume was also suggested. This method is expected to be effective in terms of safety by reducing the speed difference, which affects the severity of traffic accidents, while securing the speed improvement effect, and increasing the speed limit compliance rate of drivers by operating the speed limit that reflects the speed change due to the variation of traffic volume.