Proactive Platooning Based on C-V2X to Relieve Congestion at a Signalized Intersection

Nowadays urban traffic congestion becomes a major issue due to the increase in vehicles that lead to more commuting time,accidents,traffic violations,and high fuel consumption.Platooning is a good way to solve traffic congestion because it drives with a smaller inter-vehicle distance than human-driving.This paper proposes proactive platooning based on C-V2X(cellular vehicle-to-everything)to relieve congestion.Proactive platooning reduces the inter-vehicle distance and increases the throughput of signalized intersections through integrating the networked control platooning and computation-centralized platooning.Model and simulation experiments of proactive platooning were conducted to verify the impact of inter-vehicle distance on platooning latency,platooning safety,and traffic throughput.Simulation results show that the optimal inter-vehicle distance under proactive platooning is less than half of human-driving at a signalized intersection.

Pedestrian perception-based level-of-service model at signalized intersection crosswalks

Pedestrian level of service(PLOS)is an important measure of performance in the analysis of existing pedestrian crosswalk conditions.Many researchers have developed PLOS models based on pedestrian delay,turning vehicle effect,etc.,using the conventional regression method.However,these factors may not effectively reflect the pedestrians'perception of safety while crossing the crosswalk.The conventional regression method has failed to estimate accurate PLOS because of the primary assumption of an arbitrary probability distribution and vagueness in the input data.Moreover,PLOS categories in existing studies are based on rigid threshold values and the boundaries that are not well defined.Therefore,it is an important attempt to develop a PLOS model with respect to pedestrian safety,convenience,and efficiency at signalized intersections.For this purpose,a video-graphic and user perception surveys were conducted at selected nine signalized intersections in Mumbai,India.The data such as pedestrian,traffic,and geometric characteristics were extracted,and significant variables were identified using Pearson correlation analysis.A consistent and statistically calibrated PLOS model was developed using fuzzy linear regression analysis.PLOS was categorized into six levels(A–F)based on the predicted user perception score,and threshold values for each level were estimated using the fuzzy c-means clustering technique.The developed PLOS model and threshold values were validated with the fieldobserved data.Statistical performance tests were conducted and the results provided more accurate and reliable solutions.In conclusion,this study provides a feasible alternative to measure pedestrian perception-based level of service at signalized intersections.The developed PLOS model and threshold values would be useful for planning and designing pedestrian facilities and also in evaluating and improving the existing conditions of pedestrian facilities at signalized intersections.

Estimation of Probability of Swarming Pedestrians' Violation at Signalized Intersections in Developing Cities

We made an on-site investigation about pedestrian violation of traffic signals at a signalized intersection in Xi＇an, Shaanxi province, China. Based on it, we studied the impact of pedestrian＇s waiting time on violation decision and the impact of the number of pedestrians in colony on the probability of swarming pedestrians＇ violation. The result revealed that the probability of pedestrian violation rose with the waiting time for the pedestrians＇ green signal. Then we developed a Monte Carlo model for simulating mixed vehicles and pedestrians and used the on-site investigation data to validate the model. When traffic volume is fight, the error between the simulated values and the measured ones is 2.67%. When traffic volume is heavy, the error is 3.38%.

Study on Geometric Factors Influencing Saturation Flow Rate at Signalized Intersections under Heterogeneous Traffic Conditions

The main objective of intersection design is to facilitate the convenience, comfort, and safety of people traversing the intersection by enhancing the efficient movement of road users. The intersections on urban roads in India generally cater to heterogeneous motorized traffic, along with slow-moving traffic including pedestrians. It is therefore necessary to consider saturation flow for mixed traffic conditions to evaluate the overall operation of signalized intersections. A proper traffic model must consider varying characteristics of all the road users to effectively design and efficiently manage signalized intersections. This paper presents the results of the study on analyses of saturation flow rate conducted at signalized intersections with mixed traffic conditions in the city of Bangalore, India. Studies were carried out at 15 signalized intersections in the city of Bangalore with varying geometric factors such as width of road (w), gradient of the road (g), and turning radius (r) for right turning vehicles. Saturation flow rate computed as per Highway Capacity manual (HCM: 2000), Indonesian highway capacity manual (IHCM), and IRC SP: 41-1994 was compared with the field observations. The geometric factors, which affect the saturation flow, have been considered in this study and accordingly a new model has been proposed for determining saturation flow. It has been shown that by the introduction of the suggested adjustment factors in this paper, the saturation flow rate can give better picture of the field conditions, especially under heterogeneous traffic conditions of an urban area.

Development and Testing of an Automatic Turning Movement Identification System at Signalized Intersections

Vehicle turning movement data from signalized intersections is utilized for numerous applications in the field of transportation. Such applications include real-time adaptive signal control, dynamic traffic assignment, and traffic demand estimation. However, it is very time consuming and costly to obtain vehicle turning movement information manually. Previous efforts to simplify this process were focused on solving the problem using an O-D matrix, but this method proved to be inaccurate and unreliable with the existing data acquisition system. Another study involved the identification of vehicle turning movements from the detector information, but the presence of shared lanes led to uncertainties in vehicle matching, thus limiting application of the method only to intersections without shared lanes. In light of those unsuccessful attempts, this paper develops and tests a system called the Automatic Turning Movement Identification System (ATMIS), which estimates vehicle turning movements at a signalized intersection in real time, regardless of its geometry. The results from lab experiments as well as a field test show that the algorithm is very promising and may potentially be expanded for field applications.

Pedestrian Crash Prediction Models and Validation of Effective Factors on Their Safety (Case Study: Tehran Signalized Intersections)

The quantity and severity of traffic accidents have increased with the development of machinery life and traffic growth in cities and roads in the past 50 years. Among the road users, pedestrians are the most vulnerable groups to be exposed to high risks. Vehicle crashes with pedestrian are almost inevitable and cause injury or death to pedestrian. Crash investigation and statistical studies indicate that percentage of pedestrian deaths caused by vehicle accidents are much more than all deaths. A considerable amount of accidents occur at signalized and urban intersections which are the intensive crash places. Therefore in this paper appropriate models that could specify safety indicators have been indicated with existing information by characterized parametric and nonparametric variables for twenty signalized intersections. Categories and correlations of variables also have been investigated. Three models including Regression, Poisson, and Negative binomial with defined variables have been determined. T and chi square tests, calibration and comparison of variables have been done by curve fitting. The role of each parameter was specified in pedestrian crashes. Validating models had the following outcomes: Pedestrian crash prediction models were based on none linear relations at intersections. Predictable variables, developing extended linear models and also pedestrian crash prediction are on the basis of Negative binomial distribution which is used due to more data dispersion. As observed, the Negative binomial regression because of its more R2 correlation factor has more validity among other regression models such as linear regression and Poisson. Calibrated models are put into sensitivity analysis to study the effect of each previously mentioned parameter in overall performance. Hence much better perception of future transportation plans can be achieved by development of safety models at planning levels.

Assessing the Effects of Indirect Left Turn on a Signalized Intersection Performance: A Case Study for the Tehran Metropolitan Area

Many signalized intersections are characterized with frequent left-turn moves. Vehicles waiting for a protected left turn may form long queues, which will increase the intersection delay and negatively impact the network performance. Researchers and practitioners across various countries underline that access management leads to a smoother traffic flow. One way of access management at intersections is to eliminate the direct left-turn maneuver. This study aims to evaluate how the traffic conditions will be affected from replacing the direct left turn with the right-turn U-turn maneuver at intersections. In case of the right-turn U-turn maneuver, a vehicle turns right instead of making the left turn and travels either to the median opening or to the next intersection to make a U-turn. Two simulation models are built using the Synchro Studio and Aimsun simulation software packages based on the data, collected from one of the busiest intersections in Tehran (Iran), to quantify the effects of replacing the direct left turn with the right-turn U-turn maneuver on the intersection and network performance. Results of a comprehensive simulation analysis indicate that the proposed access management treatment not only significantly reduces the total vehicle queue length and the total delay at the considered intersection, but also decreases the total network delay and the total travel time. Furthermore, elimination of the direct left turn increases the number of vehicles entering the network.

Optimization of Crosswalk Width Based on Bi-Directional Pedestrian Crossing Time at Signalized Intersections

The effects of the interactions between bi-directional pedestrians on the crossing time and the crosswalk width are studied. Firstly,the crossing process of bi-directional pedestrians is analyzed.The total crosswalk time is divided into a discharge time and a crossing time. The interactions between bi-directional pedestrians are quantified with the drag force theory. Then,a model is developed to study the crossing time based on the kinetic energy theory and momentum theory. Subsequently,the related parameters of the proposed model are calibrated with observed information. The relationships among crosswalk width,signal time,pedestrian volume and level of service are simulated with the proposed model. The results are verified and compared with other models. The proposed model has an absolute value of relative error of 9. 38%,which is smaller than that of the Alhajyaseen model（ 15. 26%） and Highway Capacity Manual（ HCM） model（ 12. 42%）. Finally,suggested crosswalk widths at different conditions are successfully estimated with the proposed crossing time model.

Examining the Risk Factors of Rear-End Crashes at Signalized Intersections

Rear-end crashes are among the most common crash types at signalized intersections. To examine the risk factors for the occurrence of this crash type, this study involved the analysis of nine years of intersection crash records in the state of Wyoming. With that, the contributing factors related to crash, driver, environmental, and roadway characteristics, including pavement surface friction, were investigated. A binomial logistic regression modeling approach was applied to achieve the study’s objective. The results showed that three factors related to crash and driver’s attributes (commercial vehicle involvement, speeding, and driver’s age) and four factors related to environmental and roadway characteristics (lighting, weather conditions, area type, whether urban or rural and pavement friction) are associated with the risk of rear-end crash occurrence at signalized intersections. This study provides insights into the mitigation measures to implement concerning rear-end crashes at signalized intersections.

Cycle-by-Cycle Queue Length Estimation for Signalized Intersections Using Multi-Source Data

In order to estimate vehicular queue length at signalized intersections accurately and overcome the shortcomings and restrictions of existing studies especially those based on shockwave theory,a new methodology is presented for estimating vehicular queue length using data from both point detectors and probe vehicles. The methodology applies the shockwave theory to model queue evolution over time and space. Using probe vehicle locations and times as well as point detector measured traffic states,analytical formulations for calculating the maximum and minimum( residual) queue length are developed. The proposed methodology is verified using ground truth data collected from numerical experiments conducted in Shanghai,China. It is found that the methodology has a mean absolute percentage error of 17. 09%,which is reasonably effective in estimating the queue length at traffic signalized intersections. Limitations of the proposed models and algorithms are also discussed in the paper.

Delay model of signalized roundabouts

In order to evaluate the service level of roundaboutsintuitively, a new delay model of signalized roundabouts isestablished. According to traffic flow characteristics in thesignalized roundabout, vehicle delays on roundabouts aredivided into two parts： entrance delay and circulating lanedelay. Entrance delay is calculated by the delay model inHCM2010. Circulating lane delay is studied by analyzingconflict behavior in signalized roundabouts, and the delaymodels of traffic flows turning in different directions areestablished based on the motorcade analysis method. Finally,the simulation software Vissim, calibrated with field data, isused to verify the model. The simulation results show that theaverage relative error of the model is 10. 1%, meeting theaccuracy requirements. Therefore, the delay model properlyreflects the operation efficiency of a roundabout, and can thusorovide a scientific basis for the design of control schemes.

Signalized Corridor Timing Plan Change Assessment Using Connected Vehicle Data

Updates to traffic signal timing plans are expected to either improve operations or mitigate the effects of increased volumes. Longitudinal before-after studies are important when validating changes to traffic signal systems, but they have historically required field data collection as well as deployment of extensive detection and communication equipment. These infrastructure-based techniques are costly and hard to scale. This study utilizes commercially available connected vehicle (CV) trajectory data to assess the change in performance between August 2020 and August 2021 on a 22-intersection corridor associated with the implementation of a semi-automated adaptive control system. Approximately 1 million trajectories and 13.5 million GPS points are analyzed for weekdays in August 2020 and August 2021. The vehicle trajectory data is used to compute corridor travel times and linear referenced relative to the far side of each intersection to generate Purdue Probe Diagrams (PPD). Using the PPDs, operational measurements such as arrivals on green (AOG), split failures (SF), and downstream blockage (DSB) are calculated. Additionally, traditional Highway Capacity Manual (HCM) level of service (LOS) is estimated. Even though there was a 35% increase in annual average daily traffic (AADT), the weighted average vehicle delay only increased by two seconds, LOS did not change, AOG improved by 1%, and SF and DSB remained the same. Based on the small changes in operational performance and considering the increase in traffic volume it is concluded that the implementation of the semi-automated adaptive control system had a significant positive impact in the corridor. The presented framework can be utilized by agencies to use CV data to perform before-after studies to evaluate the impact of signal timing plan changes. The presented methodology can be applied to any location where CV trajectory data is available.

Temporal and spatial compliance behaviour of pedestrians under the influence of time pressure at signalized intersections:A pedestrian simulator study

Pedestrian safety is at high stakes due to the non-compliance practices of pedestrians at signalized intersections.Additionally,when pedestrians are hurrying,they deliberately engage in such unsafe behaviour.Therefore,the purpose of this study was to understand how time pressure(i.e.,feeling of hurry or saving time)affected pedestrians'decisions to follow traffic rules at signalized junctions.To achieve the study objectives,a pedestrian simulator setup was used to collect the crossing behaviour of forty participants at a four-legged signalized intersection.Non-compliance,one of the riskiest pedestrian behaviours,was examined with respect to three different forms,comprising dangerous temporal non-compliance(D-TNC),non-dangerous temporal non-compliance(ND-TNC),and spatial non-compliance(SNC)behaviour under two distinct conditions:baseline(i.e.,no time pressure)and time pressure conditions.The effects of demographics,usual walking features,and time pressure on D-TNC and ND-TNC were investigated using a multinomial regression model,while SNC behaviour was investigated using a binary regression model.It was interesting to note that the majority of the factors related to pedestrians’usual walking behaviour had an impact on all kinds of non-compliance behaviours.Importantly,the results also showcased that time pressure had a contrasting impact on D-TNC and ND-TNC behaviour whereas SNC behaviour increased under time pressure.Additionally,the varying impacts of D-TNC,ND-TNC,and SNC were also reflected in the occurrence of the crashes,which were probably triggered by discrepancies in the influence of time pressure on non-compliance behaviours.These findings highlight the need for technical solutions,educational outreach,and efficient enforcement practices to reduce pedestrians'non-compliant behaviour.

Smartphones and traffic signals:A quantitative assessment for phone usage behavior on performance of signalized intersections

Modern smartphones differ vastly from classic cellphones with enormous capabilities,changing cellphones from making phone calls and short messages to pocket-sized computers with full internet connectivity.The downside of modern phone evolution is changing drivers’behavior and phone usage addiction.Several researchers have investigated the safety implications of phone usage while driving on accidents risk.Nevertheless,the effect of phone usage on the performance of traffic facilities did not receive equal attention.Hence,this research aims to study the impact of smartphone usage on traffic signal operations.The parameters considered in the study were drivers’activity while waiting at the signal,startup lost time,and saturation flow rate.The study team covered 25 intersections in the study area,observed the activities of over 6800 drivers while waiting at the signal,and recorded their corresponding discharge headways.The study team then supplemented field data with a behavioral survey questionnaire for drivers living in the study area to interpret field observations.Finally,the collected data were processed and analyzed,resulting in mathematical models for the relationship between the reduction in saturation flow rate and the red time interval.The team found two primary conclusions.The study’s first finding was that the traditional concept for estimating startup lost time adopted by the highway capacity manual(HCM)appears inaccurate.The field results revealed that the lost times caused by other distracted drivers upstream in the queue were comparable to the estimated startup lost time following the HCM method for estimating startup lost time.The second finding was that the reduction in saturation flow rate at the traffic signal is an exponential function of the red time interval,reducing the overall capacity for the intersection and increasing the average delay.Finally,the authors suggest mitigating the problem and making recommendations for future research.

Hypoglycemic mechanism of Tegillarca granosa polysaccharides on type 2 diabetic mice by altering gut microbiota and regulating the PI3K-akt signaling pathwaye

Type 2 diabetes mellitus(T2DM)is a complex metabolic disease threatening human health.We investigated the effects of Tegillarca granosa polysaccharide(TGP)and determined its potential mechanisms in a mouse model of T2DM established through a high-fat diet and streptozotocin.TGP(5.1×10^(3) Da)was composed of mannose,glucosamine,rhamnose,glucuronic acid,galactosamine,glucose,galactose,xylose,and fucose.It could significantly alleviate weight loss,reduce fasting blood glucose levels,reverse dyslipidemia,reduce liver damage from oxidative stress,and improve insulin sensitivity.RT-PCR and Western blotting indicated that TGP could activate the phosphatidylinositol-3-kinase/protein kinase B signaling pathway to regulate disorders in glucolipid metabolism and improve insulin resistance.TGP increased the abundance of Allobaculum,Akkermansia,and Bifidobacterium,restored the microbiota abundance in the intestinal tracts of mice with T2DM,and promoted short-chain fatty acid production.This study provides new insights into the antidiabetic effects of TGP and highlights its potential as a natural hypoglycemic nutraceutical.

Influence of Bicycle Traffic on Capacity of Typical Signalized Intersection

Bicycle traffic has a significant effect on the capacity of signalized intersections. This paper divides the influence of bicyclists on vehicular flow into four types with the time durations estimated based on probability, shock wave, and gap acceptance theory. Vehicular saturation flow rate is predicted for various conditions on the basis of the speed-flow curve for the capacity of typical intersections influenced by bicycle traffic The model overcomes the limitations of the Highway Capacity Manual （HCM, 2000） method for left-turns due to data collection, and takes into account the effect of trapped bicycles on the through vehicular traffic. The numerical results show that the left-turn and through capacities predicted by the model are lower than those of the HCM method. The right-turn capacity is close to that of the HCM method at low bicycle volumes and higher than that of the HCM method at high bicycle volumes.

Study on pedestrian crossing behavior at signalized intersections

A clear understanding of pedestrian crossing behavior under mixed traffic conditions is needed for providing necessary infrastructure and also for enhancing pedestrian safety at signalized intersections. This paper attempts to analyze the crossing behavior of pedestrians like crossing speed, compliance with signal, and pedestrian-vehicular interaction under mixed traffic conditions and to iden- tify the influencing factors based on statistical tests. 775 pedestrian samples were observed from three signalized intersections in Mumbai, India for analyzing crossing behaviors and the significant factors affecting traffic signal compliance by pedestrians were identified by conducting Pearson＇s correlation co- efficient test, ANOVA test, and Student t test. Factors influencing pedestrian crossing speed had been studied and a design crossing speed had been determined for old and adult pedestrians at 0.95 m/s and 1.12 rn/s respectively. Logistic regression models had been developed in which the odds of pedestrian violation and interactions were modeled and verified. This study can help researchers and practitioners to understand pedestrian crossing behavior at signalized intersections and develop pedestrian delay mod- els under mixed traffic conditions.

Delay Estimates of Mixed Traffic Flow at Signalized Intersections in China

Two characteristics of Chinese mixed traffic invalidate the conventional queuing delay estimates for western countries. First, the driving characteristics of Chinese drivers lead to different delays even though the other conditions are the same. Second, urban traffic flow in China is often hindered by pedestrians at intersections, such that imported intelligent traffic control systems do not work appropriately. Typical delay estimates for Chinese conditions were obtained from data for over 500 vehicle queues in Beijing collected using charge coupled device （CCD） cameras. The results show that the delays mainly depend on the pro- portion and positions of heavy vehicles in the queue, as well as the start-up situations （with or without interference）. A simplified delay estimation model considers vehicle types and positions that compares well with the observed traffic delays.

Safety impacts of red light running photo enforcement at urban signalized intersections

Red light running at signalized intersections is a major safety concern in the United States. Statistics show that approximately 45 percent of crashes at intersections caused by red light running re- sult in severe injuries and fatalities, while only approximately 30 percent of all other types of intersec- tion crashes cause injuries or fatalities. Over the past decade, many US cities and counties have de- ployed red light running photo enforcement systems for signalized intersections within their jurisdictions to potentially reduce red light running related crashes. This study proposes an empirical Bayesian （ EB ） before-after analysis method that computes a weighed sum of crashes observed in the field and crashes predicted by safety performance functions （SPFs） to mitigate regression-to-mean biases for analyzing crash reduction effects of red light running enforcement. The analysis explicitly considers red light run- ning related crash types, including head-on, rear-end, angle, tuming, sideswipe in the same direction, and sideswipe in the opposite direction; and crash severity levels classified as fatal, injury, and proper- ty damage only （PDO）. A computational study is conducted to examine the effectiveness of the Chica- go program with red light running photo enforcement systems deployed for nearly two hundred signal- ized intersections. It is revealed that the use of red light running photo enforcement on the whole is pos- itive, as demonstrated by reductions in all types of fatal crashes by 4-48 percent, and injury-related an- gle crashes by 1 percent. However, it slightly raises PDO-related angle crashes and moderately increa- ses injury and PDO related rear-end crashes. The safety effectiveness of red light running photo en- forcement is sensitive to intersection location.

Capacity Reliability of Signalized Intersections with Mixed Traffic Conditions

The reliability of capacity of signalized intersections in mixed traffic conditions involving vehicles, bicycles, and pedestrians was investigated to complete the conventional, deterministic capacity calculations. Simulations using VISSIM provided estimates of capacity distributions, and demonstrated the effects of the analysis intervals on the distributions. With the random vehicle arrivals taken into account, a capacity reliability assessment method was given as a function. Assessments were also performed regarding the effects of the conflicting pedestrian and bicycle volumes on capacity reliability. The simulation indicates that the pedestrians and bicycles result in greater random fluctuations of exclusive turning lane capacities, but have less effect on the variability of shared lane capacities. Normal distributions can be used to model the capacities for intervals not less than 10 rain. At higher vehicular volumes, the capacity reliability is more sensitive to the mean and standard deviation of the pedestrian and bicycle volumes.