Modeling traffic barriers crash severity by considering the effect of traffic barrier dimensions

Traffic barriers are in widespread all around the USA as safety countermeasures for reducing the severity of run-off-road crashes. The effect of traffic barriers’ dimension had been ignored in past real-world crash studies due to the considerable cost and time needed for collecting field data. This paper presented two new analytical models to investigate the effect of different variables on the severity of crashes involving traffic barriers, and end treatments. For this reason, a field survey was conducted on over 1.3 million linear feet of traffic barriers (approximately 4,176 miles road) in Wyoming to measure traffic barriers’ geometric features like height, length, offset, and slope rate. The collected data included 55% of all non-interstate roads of Wyoming. Based on results, the crashes involving box beam barriers were less severe than the crashes involved with W-beam or concrete barriers. The traffic barriers with a height between 28 and 31 in. were found safer than the traffic barriers shorter than 28 in., while there was no significant difference between the traffic barriers taller than 31 in. to those shorter than 28 in. in terms of crash severity. The end treatments located nearer to the traffic lane had lower crash severity.

Field Study of HPTRM Combined with Vegetation and Anchor to Protect Newly Excavated Expansive Soil Slope

Anchor reinforced vegetation system(ARVS)comprises high performance turf reinforcement mats(HPTRM),vegetation and anchors.It is a new attempt to apply the system in expansive soil slope protection.The goal of this paper was to evaluate the effectiveness of ARVS in protecting newly excavated expansive soil slopes.The field tests on the bare slope,grassed slope and ARVS protective slope were carried out,including natural and artificial rainfall.During the test,the soil water content,soil deformation,and anchor axial force were monitored,and then the slope protection mechanism of ARVS was analyzed.It was found that ARVS can effectively protect expansive soil slopes compared with bare slopes and grassed slopes.The vegetation and HPTRM form a reinforced turf,and the anchors fix it to the slope surface,thus restraining the expansion deformation.The axial force on the anchor of ARVS includes frictional resistance and tensile force transmitted by HPTRM,which is maximum at the early stage of support.The neutral point of the anchor of ARVS moves deeper under atmospheric action,but the vegetation and HPTRM on the slope surface can limit this movement.

Visible light communication for intelligent transportation systems:A review of the latest technologies

In seeking to improve traffic congestion and safety on roads and highways,there has been an increased interest in intelligent transportation systems(ITS).The emerging visible light communication(VLC)technology is a new candidate to enable wireless access in ITS.The purpose of this study is to present a comprehensive review of the current studies related to VLC.Since VLC facilitates illumination and data communication simultaneously,it reduces energy consumption significantly.Additionally,VLC is immune to electromagnetic interference,provides high data security,and utilizes unregulated visible light spectrum,showing promise as a potentially cheaper alternative to existing radio frequency(RF)based technology.Moreover,recent advances in semiconductor materials and solid-state technologies have enabled the development of efficient light-emitting diodes(LEDs)and laser diodes(LDs)which are used as transmitters in a VLC system.Although 10 s of Gbits/s data rate has been demonstrated in indoor VLC links,successful implementation of it in outdoor environments requires further research to overcome the challenges presented by environmental factors,unwanted lights,non-line of sight communication,directional radiation pattern,frequent fragmentation,and so on.Besides,in recent years,semiconductor LDs have been garnering more attention since they can transmit more data over longer distances due to their high quantum efficiency and modulation bandwidth compared to LEDs.As a result,urban planners,policy-makers,transportation engineers,and vehicle manufacturers are considering LD-based VLC to facilitate vehicle-to-vehicle and vehicle-to-infrastructure communication.Thus,this paper reviews and compares the most recent developments in VLC technologies,identifies their benefits and potential use in ITS applications,discusses the probable barriers for their implementation in our existing transportation infrastructure,and suggests future research directions and recommendations to overcome these challenges.

Predicting injury severity and crash frequency:Insights into the impacts of geometric variables on downgrade crashes in Wyoming

Road deaths,injuries and property damage places a huge burden on the economy of most nations.Wyoming has one of the highest truck-related fatality rates among the states in the US.The high crash rates observed in the state is as a result of many factors mainly related to the challenging mountainous terrain in the state,which places extra burden on truck drivers in terms of requiring higher levels of alertness and driving skills.The difficult geometry of roads characteristic of mountainous terrain in terms of steep grade lengths adds extra risks of fatalities or injuries occurring as a result of a crash.These risks are more pronounced for truck-related crashes due to their weight and sizes.As part of the measures to reduce the incidence of truck-related crashes on mountainous areas,the Wyoming Department of Transportation(WYDOT)initiated a study to investigate causes of truck crashes on downgrade areas of Wyoming.Several studies have investigated the contributory factors to severe injury crashes but the focus has mostly been on level sections.This study analyzed the contributory geometric factors of truck crashes on downgrades by estimating three crash prediction negative binomial models.These models took into account the injury severity of the crashes.The results indicate that downgrade length,shoulder width,horizontal curve length,number of lanes,number of access points and truck traffic on the highway all impact truck-related crashes and injury frequencies ondowngrades in Wyoming.The results of this study will be helpful to future downgrade road design policy aimed at reducing downgrade truck related crashes.