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문제 정의
- It is hoped that the development of a traffic accident estimation model in this research will pave the way for the establishment of a suitable method of preventing traffic accidents at rural roadway segments. This research was based on the assumption that the characteristics of traffic accidents follow Poisson distribution and can be compared by developing suitable statistical models. The results of this research are as follows:
제안 방법
- Based on the research results of the developed traffic accident estimation model for geometric structures, the elasticity was analyzed for each explanation variable according to the change in values of the variables. As shown in Table 6, in the case of multilane roadway segments, the higher the radius (1000/R) is, the higher the increase in the values of the variable, and the lower the radius is, the bigger the values of the variable, which means that sudden curves are formed.
- Rural roadway segments outside the capital region, or outside metropolitan areas, and on plains and downhill areas, were chosen for this study. Field research was executed as follows: First, based on data obtained from past researches, the variables affecting the frequency of traffic accidents were arranged, and the research areas and roadway axes were chosen. Second, the final variable candidates were chosen by carrying out some sections of the past field researches, and by supplementing the field research plan.
- Based on such results, it can be used to choose the priority design element for designing rural roadway segments. For the analysis of the effects of the various design elements on the frequency of traffic accidents, the analysis scope is focused on two-way lane and multilane roadway segments. Also, table 3 explains study sites statistics.
- Such models’ results are presented in Table 4 and 5. For the use of the developed traffic accident estimation model for rural multilane roadway segments, the following variables were chosen: EXPO, radius, HC, VC, guardrail, crosswalk, terrain, land use, and bus stop. EXPO, grade, driveway, lighting, Terrain, bus stop, median, land use, and crosswalk are shown in the two-way lane roadway segment.
- Therefore, to reduce the traffic accidents at roadway segments, the traffic, roadway, and traffic operation conditions should be analyzed when designing roads. In addition, this research focused on rural two-lane and multilane roadway segments and developed a traffic accident estimation model through the application of a statistical technique. Through these, a suitable traffic accident prevention method was developed for rural roadway segments.
- Main variables were chosen to estimate their effects on traffic accident occurrence at rural roadway segments, and the safety at such rural roadway segments was assessed or estimated. In this research, it was assumed that there are different factors that affect the safety at two-way lane and multilane roadway segments, and a traffic accident estimation model was developed by dividing the two-way lane and multilane roadway segments. The results showed that the [+] variables that increase traffic accidents at rural multilane roadway segments are EXPO, radius, VC, guardrail, crosswalk, terrain, land use, and bus stop; those that increase [+] traffic accidents at two-way lane roadway segments are EXPO, driveway, median, land use, and crosswalk; and those that reduce (-) traffic accidents at two-way lane roadway segments are grade (0%) and lighting facilities.
- (1994), Brinkman and Percbonok (1979) in their research results. In this research, to analyze the relationship between the frequency of traffic accidents and the various explanation variables that had been gathered, the changes in the elements (e.g., geometric structure) were segmented for each section at a continuous roadway segment. Moreover, the sections where traffic accidents have occurred and those where no traffic accident has occurred were simultaneously considered and should be applied in the construction of a traffic accident estimation model.
- In this research, two alternative models for each type of roadway segment that was developed from the Hurdle model were developed. These models can used to determine significant variables affecting accidents.
- To determine the effect of the various design elements on the frequency of traffic accidents, to avoid repeated effects between the explanation and subordinate variables, and to choose the variables for securing each variables independence, the design elements were analyzed under the condition where the reliable level of correlation among the variables was 90%. In this study, Poisson, negative binomial regression, and Hurdle models were developed and analyzed. The research results showed that the used roadway segment had too many zeros in its traffic accident frequency figure.
- Field research was executed as follows: First, based on data obtained from past researches, the variables affecting the frequency of traffic accidents were arranged, and the research areas and roadway axes were chosen. Second, the final variable candidates were chosen by carrying out some sections of the past field researches, and by supplementing the field research plan. Third, through field researches, the geometric structure of roadways and traffic condition variables were collected.
- The scope of the explanation variables in the results showed that data regarding the geometric structure of roadways, traffic conditions, and other variables can be collected. The geometric structure consisted of the road variables (curve radius, vertical curve, traveled width, roadway segment length, driveway lanes, shoulder shape and width) and the roadway design variables (number of lighting facilities, median shape and width). The traffic condition variables were limited speed, traffic volume, heavy vehicle volume, restricted driving facilities, and terrain, and the other variables were the relevant land-uses and the number of crosswalks, bus stops, and visibility improvement facilities.
- The past researches on roadway segments, however, analyzed the effects of certain factors on the traffic accident occurrence rate by organizing the individual geometric structures of the roads, but there is a dearth of researches on the development of a traffic accident estimation model. Therefore, this research aimed to develop a traffic accident estimation model by applying a statistical technique on rural two-lane and multilane roadway segments. It is hoped that the development of a traffic accident estimation model in this research will pave the way for the establishment of a suitable method of preventing traffic accidents at rural roadway segments.
- shows the research sections for the traffic accident analysis at rural roadway segments. This research combined all of the data collected from Region A and Region B, and divided the data into two-lane and multilane categories.
- This research used ρ2(Likelihood ratio statistic) to determine the final models in order to conduct analyses significant factors affecting accidents.
- This research was focused on rural roadway segments, and traffic accident models were developed for such roadway segments. A traffic accident model for urban roadway segments is also needed, though.
- 0. This traffic accident estimation model was to be used to prove the relation between the main explanation variables and the frequency of traffic accidents, as well as to assess the safety of the analysis section through traffic accident estimation. To determine the effect of the various design elements on the frequency of traffic accidents, to avoid repeated effects between the explanation and subordinate variables, and to choose the variables for securing each variables independence, the design elements were analyzed under the condition where the reliable level of correlation among the variables was 90%.
대상 데이터
- Rural roadway segments outside the capital region, or outside metropolitan areas, and on plains and downhill areas, were chosen for this study. Field research was executed as follows: First, based on data obtained from past researches, the variables affecting the frequency of traffic accidents were arranged, and the research areas and roadway axes were chosen.
이론/모형
- A traffic accident estimation model was developed using LIMDEP 8.0. This traffic accident estimation model was to be used to prove the relation between the main explanation variables and the frequency of traffic accidents, as well as to assess the safety of the analysis section through traffic accident estimation.
- ”Important data may be lost in the analysis when the fact that the data obtained through the use of the existing model and the traditional reasoning method includes too many zeros is not considered. To address this problem, the Hurdle model was applied in this research. The following is an explanation of such model.
성능/효과
- 1. The research results showed that although traffic accidents follow Poisson distribution, the used roadway segment had too many zeros in its traffic accident frequency figure. Therefore, it is required to explain such high frequency of zero counts in the traffic accident data.
- 2. Main variables were chosen to estimate their effects on traffic accident occurrence at rural roadway segments, and the safety at such rural roadway segments was assessed or estimated. In this research, it was assumed that there are different factors that affect the safety at two-way lane and multilane roadway segments, and a traffic accident estimation model was developed by dividing the two-way lane and multilane roadway segments.
- Researchers have also examined the effect of vertical curves on safety but did not establish a clear relationship between vertical curves and accident frequency. In this study, it was found that traffic accident occurrence probability is higher in the case of uphill road sections at vertical curves (t=7.027). This finding agrees with the results of the research conducted by Harwood et al.
- Many previous researches revealed that raised median have a trade-off safety effect: placing a curb in the median will largely reduce cross-median accidents but may increase sideswipe crashes and crashes that result from vehicles being deflected back into the traffic stream. In this study, it was found that traffic accidents increased in roads where a median had been installed. This finding was also shown in the results of the research that was conducted by Donnell et al.
- In this study, Poisson, negative binomial regression, and Hurdle models were developed and analyzed. The research results showed that the used roadway segment had too many zeros in its traffic accident frequency figure. Therefore, it was found that the Hurdle model is more suitable than the Poisson or negative binomial regression model for explaining the data that were used in the research, as shown in Fig 4.
- In the research conducted by Sheffer(1999), it was assumed that the intersection traffic accident rate is affected by the lead and lag left-turn phase methods, among the different signaling phase methods. The results of the analysis of the target intersection lead left-turn phase showed a 50% lower traffic accident rate, or higher than that of the lag left-turn phase. In addition, Bauer(1996) analyzed the correlation between the traffic volume and the geometric structure of the plane intersection, and developed a statistical traffic accident model.
- (2000) found that as the slope of the roadway segment increases, the number of traffic accidents also tends to increase. The results of their analysis revealed that the traffic accidents increased by 3-14% when the slope was between 2 and 8%. Therefore, in the study conducted by Zegeer et al.
- In addition, Bauer(1996) analyzed the correlation between the traffic volume and the geometric structure of the plane intersection, and developed a statistical traffic accident model. The results of their research also showed that the traffic volume has a greater effect on the frequency of traffic accidents than the geometric structure of the intersection does. Moreover, Bonneson(1993) analyzed the relation between the traffic volume at intersections and the frequency of traffic accidents using negative exponential distribution, refined the relation between major and minor roadway traffic volume and the frequency of traffic accidents, and developed a traffic accident estimation model.
- (1986). The results of their researches showed that countermeasures are needed to prevent traffic accidents at vertical-curve interchange sections. The speed decrease of a big vehicle in an uphill section will affect another speeding vehicle and may cause traffic chaos.
- Thus, it is the presence of additional conflict points at roadway segments that is associated with crashes. The results of this study also showed that the higher the driveway density is, the lower the rate of vehicle to vehicle traffic accidents at roadway segments. These findings support the notion that effective access management can improve safety at roadway segments.
- David and Norman(1976) analyzed the frequency of traffic accidents according to the urban- and rural-area traffic volumes, using comparative analysis. The results showed that at unsignalized intersections in urban areas, if the number of traffic accidents is 20,000 veh/day or less, the 3-leg intersection and 4-leg intersection traffic accident frequency will be similar, but if the number of traffic accidents at an unsignalized intersection is 20,000 veh/day or more, the frequency of traffic accidents at four leg intersections will be more than twice the frequency of traffic accidents at three-leg intersections.
- The results showed that the [+] variables that increase traffic accidents at rural multilane roadway segments are EXPO, radius, VC, guardrail, crosswalk, terrain, land use, and bus stop; those that increase [+] traffic accidents at two-way lane roadway segments are EXPO, driveway, median, land use, and crosswalk; and those that reduce (-) traffic accidents at two-way lane roadway segments are grade (0%) and lighting facilities.
- This traffic accident estimation model was to be used to prove the relation between the main explanation variables and the frequency of traffic accidents, as well as to assess the safety of the analysis section through traffic accident estimation. To determine the effect of the various design elements on the frequency of traffic accidents, to avoid repeated effects between the explanation and subordinate variables, and to choose the variables for securing each variables independence, the design elements were analyzed under the condition where the reliable level of correlation among the variables was 90%. In this study, Poisson, negative binomial regression, and Hurdle models were developed and analyzed.
후속연구
- Therefore, this research aimed to develop a traffic accident estimation model by applying a statistical technique on rural two-lane and multilane roadway segments. It is hoped that the development of a traffic accident estimation model in this research will pave the way for the establishment of a suitable method of preventing traffic accidents at rural roadway segments. This research was based on the assumption that the characteristics of traffic accidents follow Poisson distribution and can be compared by developing suitable statistical models.
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