Automatic Lane-Level Intersection Map Generation using Low-Channel Roadside LiDAR

A lane-level intersection map is a cornerstone in high-definition(HD) traffic network maps for autonomous driving and high-precision intelligent transportation systems applications such as traffic management and control, and traffic accident evaluation and prevention. Mapping an HD intersection is time-consuming, labor-intensive, and expensive with conventional methods. In this paper, we used a low-channel roadside light detection and range sensor(LiDAR) to automatically and dynamically generate a lane-level intersection, including the signal phases, geometry, layout, and lane directions. First, a mathematical model was proposed to describe the topology and detail of a lane-level intersection. Second, continuous and discontinuous traffic object trajectories were extracted to identify the signal phases and times. Third, the layout, geometry, and lane direction were identified using the convex hull detection algorithm for trajectories. Fourth, a sliding window algorithm was presented to detect the lane marking and extract the lane, and the virtual lane connecting the inbound and outbound of the intersection were generated using the vehicle trajectories within the intersection and considering the traffic rules. In the field experiment, the mean absolute estimation error is 2 s for signal phase and time identification. The lane marking identification Precision and Recall are96% and 94.12%, respectively. Compared with the satellite-based,MMS-based, and crowdsourcing-based lane mapping methods,the average lane location deviation is 0.2 m and the update period is less than one hour by the proposed method with low-channel roadside LiDAR.

Technical Feasibility Study of Passenger Rail Service along the West Route between Las Vegas and Los Angeles

The study evaluates the feasibility of running passenger train service from Las Vegas, NV on the Union Pacific Railroad (UPRR), to Barstow, on the Burlington Northern Santa Fe (BNSF) track, to Mojave on UPRR track again, and to Lancaster connecting Metrolink to their destinations in Southern California. In this study, the railroad infrastructure was inventoried and issues related to running the passenger service were identified. Passenger train operation was evaluated based on the Rail Traffic Controller (RTC) simulation model. The performance measures of passenger trains including travel time, overall delay and average speed are analyzed. The uncertainty in freight flow and its impact on providing the passenger service is addressed by conducting a sensitivity analysis. The conclusion is that the existing railroad infrastructure is sufficient to provide a passenger train service from Las Vegas to Los Angeles. From an operational perspective, the passenger train is not expected to influence freight trains’ performance on the existing railroads. When freight train flows are increased to 50%, the influence of passenger train service on the freight operation is still minimal. This study recommends restoring a platform at the Las Vegas Station. At the Mojave Station, special care should be given on running the passenger trains where there is no direct railroad connection from BNSF to UPRR. Platforms and walkways require construction at the Lancaster Station for transferring passengers between the Metrolink trains and X-Train. Transferring the passenger train at this station involves stopping the train on mainline and coordinating the operations between different railroads.

Modeling mechanistic responses in asphalt pavements under three-dimensional tire-pavement contact pressure

A three dimensional finite element program incorporating actually measured vertical tire-pavement contact pressure(TPCP) was utilized for modeling the mechanistic responses in asphalt concrete(AC) layers by simulating various vehicle motions:stationary and non-stationary(i.e.in acceleration or deceleration mode).Analysis of the results indicated the following items.1) It is critical to use the vertical TPCP as the design control criteria for the tensile strains at the bottom of the AC layer when the base layer modulus is lower in magnitude(e.g.≤400 MPa);however,when the base layer modulus is higher in magnitude(e.g.≥7 000 MPa),the horizontal TPCP and the tensile strains in the X-direction at the surface of the AC layer should also be considered as part of the design response criteria.2) The definition of "overload" needs to be revised to include tire pressure over-inflation,i.e.,a vehicle should be considered to be overloaded if the wheel load exceeds the specification and/or the tire inflation pressure is higher than the specification.3) Light trucks have more structural impact on the strain responses and pavement design when the thickness of the surfacing AC layer is thinner(e.g.≤50 mm).4) The acceleration of a vehicle does not significantly impact the AC surface distresses such as rutting at the top of the upgrade slopes or intersections;however,vehicle deceleration can dramatically induce horizontal shear strains and consequently,aggravate shoving and rutting problems at the highway intersections.Evidently,these factors should be taken into account during mechanistic stress-strain modeling and structural design of asphalt pavements.

Centrifugal model test and numerical simulation of vertical earth pressure on soft foundation box culvert

To obtain the vertical earth pressure on a soft foundation box culvert and investigate the interaction of the soil-culvert-foundation system, both a centrifugal model test and a numerical simulation were conducted and the comparisons with the current methods to determine the load on a culvert were completed. The results of the model test and numerical analysis are in satisfactory agreement, which shows that the direction of the shear stress between the culvert and the adjacent embankment depends on the differential settlement between them. A vertical earth pressure concentration appears on the culvert with a rigid piles foundation because of a downward shear stress. The ratio of the load on a soft foundation culvert and the overburden pressure above the culvert raises first and then decreases as the backfill height increases. In order to reduce the load on a culvert, it is suggested to limit the stiffness difference of the foundations under the culvert and embankment and to use a light backfill over the culvert.

Removal of Cd(Ⅱ)and Pb(Ⅱ)from soil through desorption using citric acid:Kinetic and equilibrium studies

The desorption test was conducted to evaluate the desorption behavior of Pb(Ⅱ)and Cd(Ⅱ)using citric acid.The influential factors that were considered included initial Pb(Ⅱ),Cd(Ⅱ)contamination levels in soil,concentration of citric acid,reaction time,soil pH value and ionic strength.The test results indicated that the desorption was a rapid reaction(less than 6 h),and the removal percentages of Cd(Ⅱ)and Pb(Ⅱ)increased with the increasing contamination levels,concentration of citric acid and the addition of Na^+,Ca^(2+),Na^+, Cl~– and the chelating of organic ligands.

路面灌封料性能检测新方法的开发

在道路日常养护中,采用灌封料填封路面裂缝是一种常用的方法。然而,目前市场上灌封料的粘结失效发生得很快。灌缝料失效的主要原因可以分为两类:灌封料与路面的粘结失效和灌封料自身内部失效。尽管这两种失效都可能导致道路结构寿命的衰减,但前者是主要的。目前,虽然已经有一些试验方法来评价灌缝料特性,但这些方法或耗时较长,或判断标准过于主观;更重要的是,这些方法的试验结果与灌封料实际应用情况的相关性并不好。针对这些问题,该文提出了一种即耗时短又操作方便的试验方法以评价灌封料的粘结性能。

经验贝叶斯前后对比方法评估事故修正系数的精确度分析

事故修正系数(措施安全效果)的评估是交通安全管理的重要环节,经验贝叶斯(EB)方法是目前最先进、首选的方法。该方法能够解决回归到均值的问题并提高评估精度,然而,尚未有学者对EB方法所得到事故修正系数的精确度进行细致的分析,本论文旨在填补该项空白,并重点针对事故修正系数的标准差进行分析。论文采用了模拟与实际观测两项数据对EB方法进行了分析,结果表明:1)EB方法得到的事故修正系数与理论值比较接近;2)EB方法所得到事故修正系数的标准差并不能反映真实值,估计值不随真实值的变化而变化;3)基于实际数据的分析表明EB方法往往低估事故修正系数的标准差。交通安全研究人员应当注意在使用EB方法评估安全效果时,事故修正系数的方差可能存在偏差,有必要进一步优化EB方法中方差的算法。

Analysis and O-D Demand Estimation of a Public Bike-Sharing Program in Las Vegas

Bike-share systems are an effective way of mitigating congestion on the road. In addition, bike-share systems have been built in universities to serve for trips to work/commuting as well as the trips on campus. In Las Vegas, a bike-share system was proposed at the University of Nevada, Las Vegas. This study analyzed factors that influence the usage of bike-share program and estimated the origin-destination demand. To achieve these objectives, first, a literature review was conducted on university bike-sharing systems in the U.S. and abroad. Then, a survey with a questionnaire was distributed to UNLV to obtain the users’ preferences to the locations of the proposed bike-share stations and their likelihood and frequency to use the bike-share program. In total, 241 faculty, staff, and students responded to the survey. About 50% of those participating in the survey expressed willingness to use the bike-share system for commuting and 60% said they are willing to use bike share for on-campus travel. Commuting and on-campus travel are two different types of travel, and the factors to determine whether an individual would use the bike-share system are quite different for each. It was estimated that there would be 3450 members for a bike-share program at UNLV, each making bicycle trips with varying frequencies, producing 1966 trips per day.

Determination of the Size of a Proposed Bike-Sharing Program in Las Vegas, Nevada

Bike-share systems have been installed in cities worldwide as a way to attract travelers to use transit rather than the automobile. This has been proved to be an effective way of mitigating congestion on the road. The objective of this study is to develop a method to determine the size of the bike-share program in terms of the number of bicycles, the number and location of the stations, the number of docks at each station. To achieve the objectives of this study, a literature review was conducted on university bike-sharing systems in the U.S. and abroad. Various cases of bike-share programs were analyzed, in which each case consisted of a different number and location of bike-share stations. The demand corresponding to these stations was used as the input to a simulation model developed in this study to determine the number of docks in stations and bicycles in the system on and around campus at UNLV. These sizing parameters of the bike-share system then were used in a cost and benefit analysis to determine which cases could achieve maximum benefit, given a limitation of the initial costs. It was found that provision of one peripheral station and three internal stations at strategic locations provide relatively higher benefit cost ratio at lower initial cost.

Uncovering the influence of ChatGPT's prompts on traffic safety information using text mining approach

ChatGPT has emerged as a promising advanced large language model that needs prompt to gain information.However,designing a good prompt is not an easy task for many end-users.Therefore,this study intends to determine the amount of information gained because of varied amounts of information in the prompt.This study used two types of prompts,initial and improved,to query the introduction sections of 327 highly cited articles on traffic safety.The queried introduction sections were then matched with the corresponding human-written introduction sections from the same articles.Similarity tests and text network analysis were used to understand the level of similarities and the content of ChatGPT-generated and human-written introductions.The findings indicate the improved prompts,which have the addition of generic persona and information about the citations and references,changed the ChatGPT's output insignificantly.While the perfect similar contents are supposed to have a 1.0 similarity score,the initial and improved prompt's introduction materials have average similarity scores of 0.5387 and 0.5567,respectively.Further,the content analysis revealed that themes such as statistics,trends,safety measures,and safety technologies are more likely to have high similarity scores,irrespective of the amount of information provided in the prompt.On the other hand,themes such as human behavior,policy and regulations,public perception,and emerging technologies require a detailed level of information in their prompt to produce materials that are close to human-written materials.The prompt engineers can use the findings to evaluate their outputs and improve their prompting skills.

利用修正的MEPDG损伤模型进行混合料服务寿命模拟和对比

沥青混凝土路面新材料的推广,需要适宜的技术经济评价工具。结合改性沥青费用有效性分析的实例,简要介绍了利用修正后的美国力学经验设计指南损伤模型进行新材料路用价值分析的方法。为评估某改性沥青的路用价值,结合当地材料的物理和环境参数,对通用损伤模型进行标定,并运用蒙特卡罗方法,在现场调查的基础上进行了传统沥青混合料和改性沥青混合料的路面响应模拟和服务寿命预估。结果显示:在一定条件下,采用改性沥青混合料的路面工程项目,其服务寿命比对应的传统沥青混凝土路面长,而寿命周期费较低;该方法得出的结论与现有文献的相关结论一致,可用于新材料的路用性能评价和项目级的决策支持。

Investigation of accuracy of pavement mechanistic empirical prediction performance by incorporating Level 1 inputs

The recently developed AASHTOWare pavement mechanistic empirical(M-E)design requires advanced characterization of pavement materials.In particular,M-E Level 1 analysis requires materials input parameters to be obtained from the laboratory test results.In cooperation with the New Mexico Department of Transportation(NMDOT),six pavement sites were selected to compare M-E Level 1 predicted performances from laboratory tested data with the field performances.Pavement materials such as subgrade,base,asphalt concrete,binder,aggregate,etc.,were collected from these pavements sites during construction.Laboratory dynamic modulus,fatigue endurance limit(FEL),dynamic shear rheometer,and resilient modulus tests were conducted on the collected materials.Using these parameters,pavement sections,as constructed,were modeled and analyzed in M-E at Levels 1,2 and 3.The predicted distress quantities for international roughness index(IRI)and rutting were compared with the field collected data as well as among the three design levels.The analysis results demonstrated that M-E overpredicts IRI and rutting in the pavement compared to the field performance.It was also observed that Level 1 showed the lowest rutting,whereas the maximum rutting was found at Level 2.The dynamic modulus of AC layer was underpredicted at Levels 2 and 3 resulting in higher rutting and IRI.

Application of machine learning tools in classifying pedestrian crash types: A case study

Crash occurrence is a complex phenomenon,and crashes associated with pedestrians and bicyclists are even more complex.Furthermore,pedestrian-and bicyclist-involved crashes are typically not reported in detail in state or national crash databases.To address this issue,developers created the Pedestrian and Bicycle Crash Analysis Tool(PBCAT).However,it is labour-intensive to manually identify the types of pedestrian and bicycle crash from crash-narrative reports and to classify different crash attributes from the textual content of police reports.Therefore,there is a need for a supporting tool that can assist practitioners in using PBCAT more efficiently and accurately.The objective of this study is to develop a framework for applying machine-learning models to classify crash types from unstructured textual content.In this study,the research team collected pedestrian crash-typing data from two locations in Texas.The XGBoost model was found to be the best classifier.The high prediction power of the XGBoost classifiers indicates that this machine-learning technique was able to classify pedestrian crash types with the highest accuracy rate(up to 77%for training data and 72%for test data).The findings demonstrate that advanced machine-learning models can extract underlying patterns and trends of crash mechanisms.This provides the basis for applying machine-learning techniques in addressing the crash typing issues associated with non-motorist crashes.

Safety effectiveness of roadway conversion with a two way left turn lane

In urban or suburban areas with a large number of access points, four-lane undivided highways are prone to crashes due to left-turning and through movements in a single lane. Many studies recommended expensive countermeasures like conversion from undivided to divided road with physical separation. One inexpensive alternative is reconfiguring the existing roadways by either increasing or decreasing the number of lanes. This study investigated the safety impact of converting four lane undivided roadways （4U） to five lane undivided roadways （ST） with a two way left turn lane （TIkrLTL）. This study used Empirical Bayes method to determine the safety impact of this inexpensive countermeasure. In this study, data from eight sites from Louisiana were collected for investigation, and site- specific crash modification factor （CMF） values were calculated. Although ST is usually not preferable due to its exposure of higher number of crashes in the existing literature, the findings of the current study indicated a positive safety impact. The benefit-cost ratio of this conversion ranges from 97 to 379. The current findings indicate that conversion of 4U to 5T is a feasible inexpensive solution for urban roadways with lower volume and a limited number of driveways.

The role of crosswalk-related features on drivers' spatial yielding compliance at signalized midblock crosswalks

The drivers’yielding distance to pedestrians at midblock crosswalks affects pedestrians’perceived safety.This distance can be influenced by either crosswalk-related or noncrosswalk.In most cases,crosswalk-related features are readily available or easy to collect compared to non-crosswalk features.However,the extent to which crosswalk-related features affect the spatial yielding compliance is not clear.This study evaluated the role of combined crosswalk-related features on drivers’spatial yielding compliance at signalized midblock crosswalks.The study used observational survey data collected from fifteen flash-based signalized midblock crosswalks located in Las Vegas,Nevada.Three logistic regression models,with crosswalk-related features only,non-crosswalk features only,and combined features,were developed and compared.It was revealed that the performance difference between the model with crosswalk-related features only and combined features was insignificant.This study found that the presence of state’s law signs,“PED XING”signs,and placement of rectangular rapid flashing beacons(RRFBs)on the advanced pedestrians crossing signs(APCSs),are significant factors for high spatial yielding compliance.On the contrary,the yield line’s presence at a distance greater than 40 ft from the crosswalk,presence of one stage crossing,and high Annual Average Daily Traffic(AADT)negatively affects the spatial yielding compliance.Moreover,the findings suggest that researchers should be careful about excluding the non-crosswalk features from the analysis.To improve spatial yielding compliance,several recommendations that the city planners and engineers can adopt are provided.

Calibration methodology for microscopic traffic simulation models of land ports of entry along the US-Mexico border

Non-commercial Land Ports of Entry(LPOEs)are unique transportation facilities controlling the ingress and egress of passenger vehicles from Mexico to the United States and vice versa.The calibration of microscopic traffic simulation models of non-commercial LPOEs requires a deep understanding of operational processes and driving behavior at these facilities.This paper provides a methodology to guide modelers in calibrating microscopic traffic simulation models of non-commercial LPOEs.The methodology establishes a common framework for modeling operational processes and traffic operations.Moreover,the methodology includes the value of four state variables that characterizes operations of passenger vehicles at non-commercial LPOEs.These variables are speed,acceleration,deceleration,and headway.The authors evaluated this methodology using the Otay Mesa non-commercial LPOE as a case study.Results showed that this methodology could be potentially used to model non-commercial LPOEs along the US-Mexico border and other border regions worldwide.