Introduction

Studies in weather-affected traffic collisions have mainly focused on rain and snow, which can be referred to as highly variable and non-recurrent events. On the other hand, although solar light is among the natural phenomena that regularly and negatively influences the physical and mental health of drivers, research efforts to quantitatively examine the effect of solar glare on traffic collisions are insufficient. Therefore, this study investigates that sunlight interferes with the driver's vision, causing speed variance, which increases the likelihood of a traffic accident.

Method

A comprehensive methodology was proposed to determine the temporal range where solar glare affects driving with respect to the position of the Sun, road geometry, and driver's field of vision with the aid of GIS analysis. Besides, vehicle speed variance, which is a traffic flow characteristics and a risk factor involved in traffic collisions, during traffic conditions affected and unaffected by solar glare were statistically evaluated using ANOVA tests. Then, the proposed methodology was verified and confirmed taking 20 segments of the Namhae Expressway in Busan, Korea, as a case study.

Results

Vehicle speed variance was statistically greater when it was affected by solar glare than when not affected, and this effect was more pronounced on westbound segments than in eastbound segments. This is because solar glare influences eastbound traffic early in the morning, when traffic demand is not high enough to interfere with driving. On the other hand, westbound traffic is affected during the evening commute, when much more vehicles influence driving conditions.

Conclusions

Vehicle speed variance due to solar glare takes place, and can be temporally and spatially identified on all east-west roads. It was found that the speed deviation was greater during the time affected by the sun glare, which can increase the probability of traffic accidents like investigated in the related study efforts. Particularly, because westbound traffic is more heavily affected by solar glare than eastbound traffic, more active measures should be implemented and proactively reflected in designing road geometry to improve traffic safety.

中文翻译：

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太阳眩光强度对车速变化的影响

介绍

受天气影响的交通冲突的研究主要集中在降雨和降雪，这可以称为高度多变和非周期性事件。另一方面，尽管太阳光是经常并负面影响驾驶员身体和心理健康的自然现象之一，但定量研究太阳眩光对交通冲突影响的研究工作仍不足。因此，本研究调查了太阳光会干扰驾驶员的视力，导致速度变化，从而增加发生交通事故的可能性。

方法

提出了一种综合的方法，可以借助GIS分析来确定太阳眩光影响驾驶员相对于太阳的位置，道路几何形状和驾驶员视野的时间范围。此外，使用方差分析（ANOVA test）统计评估了在受阳光刺眼影响和不受太阳眩光影响的交通状况期间的车速变化，这是交通流量的特征，也是交通冲突中的危险因素。然后，以韩国釜山市南海高速公路的20个路段为例，对所提出的方法进行了验证和确认。

结果

受到日照影响时，车速方差在统计上要大于未受日照影响时的方差，并且这种影响在西行路段比在东行路段更明显。这是因为当交通需求不足以干扰驾驶时，太阳眩光会在清晨影响东行交通。另一方面，当更多的车辆影响行车条件时，晚上通勤会影响西行交通。

结论

由于太阳眩光引起的车速变化会发生，并且可以在所有东西向道路上在时间和空间上进行识别。结果发现，在受太阳眩光影响的时间内，速度偏差较大，这可能会增加交通事故发生的可能性，如相关研究工作中所调查的那样。特别是，由于西行交通比东行交通受太阳眩光的影响更大，因此在设计道路几何形状以提高交通安全性时应采取更积极的措施并积极反映出来。