Speed Limit Value Research Articles

Bi-objective simulation optimization for online feedback control of variable speed limits considering uncertain traffic demands and compliance behaviors

Abstract Variable Speed Limits (VSL) stand out as a well-established and effective strategy to alleviate traffic congestion and enhance traffic safety on motorways. It allows Variable Message Signs (VMSs) to dynamically determine the speed limits according to real-time traffic states. This paper introduces an innovative online feedback control approach designed to regulate speed limit values on Variable Message Signs (VMSs), addressing multiple bottlenecks while considering their spatiotemporal constraints. Moreover, we offline optimize the gain coefficients of this feedback control approach in the simulation-based optimization (SBO) framework. Specifically, with average and variance of space-mean speeds as bi-objectives, a stochastic SBO model considering uncertain traffic demands and compliance behaviors is established and solved by a bi-objective surrogate-based promising area search (BOSPAS) algorithm. Real-field experiments conducted in Edmond City demonstrate the well-performing bi-objectives of the proposed approach, especially in handling uncertain compliance behaviors and traffic demands. Compared with the uncontrolled scenario, the feedback control schemes with the offline optimized gain coefficients improve the average and variance of space-mean speeds by up to 16.2% and 20.8%, respectively. Meanwhile, by the comparison of detailed performances, it is found that the optimized control schemes perform better than the uncontrolled scheme from the overall and local aspects. In conclusion, this study puts forward a general framework that applies an online feedback control approach with gain coefficients optimized offline by an SBO method to deal with real-time decision-making problems under uncertainties.

Differential variable speed limit control strategy consider lane assignment at the freeway lane drop bottleneck

Reduction in the number of lanes (lane drop) is typical on freeways due to road design, incidents, or road maintenance. As traffic demand increases, the bottleneck becomes activated because of there are many of vehicle lane-changing behaviors at the bottleneck. At the same time, the traffic density increases, resulting in a capacity drop phenomenon at the bottleneck. The degree of the capacity drop is also closely related to the traffic density at the bottleneck. Variable Speed Limit (VSL) is a widely used Active Traffic Management (ATM) method. In traditional research, most VSL control strategies consider all lanes uniformly and set uniform dynamic speed limits. However, traffic varies by lane. This study proposed a differential variable speed limit (DVSL) control strategy for each lane considering lane assignment. The DVSL control strategy sets the dynamic speed limit for each lane to attract a certain number of vehicles to change lanes before the bottleneck and reduce the impact of traffic capacity drop. This strategy is simulated based on extending the cell transmission model (CTM) to multi-lane. The multi-level iterative optimization algorithm obtains each lane's dynamic speed limit values. The experimental results show that the proposed DVSL control strategy can alleviate traffic congestion and improve efficiency. Total travel time (TTT) improved by 7.48 % compared to the no-control measures.

Variable Speed Limit Control for the Motorway–Urban Merging Bottlenecks Using Multi-Agent Reinforcement Learning

Traffic congestion is a typical phenomenon when motorways meet urban road networks. At this special location, the weaving area is a recurrent traffic bottleneck. Numerous research activities have been conducted to improve traffic efficiency and sustainability at bottleneck areas. Variable speed limit control (VSL) is one of the effective control strategies. The primary objective of this paper is twofold. On the one hand, turbulent traffic flow is to be smoothed on the special weaving area of motorways and urban roads using VSL control. On the other hand, another control method is provided to tackle the carbon dioxide emission problem over the network. For both control methods, a multi-agent reinforcement learning algorithm is used (MAPPO: multi-agent proximal policy optimization). The VSL control framework utilizes the real-time traffic state and the speed limit value in the last control step as the input of the optimization algorithm. Two reward functions are constructed to guide the algorithm to output the value of the dynamic speed limit enforced within the VSL control area. The effectiveness of the proposed control framework is verified via microscopic traffic simulation using simulation of urban mobility (SUMO). The results show that the proposed control method could shape a more homogeneous traffic flow, and reduces the total waiting time over the network by 15.8%. In the case of the carbon dioxide minimization strategy, the carbon dioxide emission can be reduced by 10.79% in the recurrent bottleneck area caused by the transition from motorways to urban roads.

A dynamic rescheduling and speed management approach for high-speed trains with uncertain time-delay

This paper studies the problem of rescheduling trains with speed management in uncertain disruptions that lead to temporary speed restrictions (TSRs) in high-speed railway systems. The disruption uncertainties are that the coverage and speed limit value of TSRs change randomly over time, and the start and end times of TSRs are unknown in advance. First, a mixed-integer linear programming model is formulated to reduce the total train traveling times and improve the passenger comfortability. The solutions of the model provide simultaneously the optimal train rescheduling strategies and train speed control strategies. Second, a rolling horizon algorithm is applied in consideration of the disruption uncertainties. The rolling horizon algorithm updates and solves the model in every time horizon, according to the disruption information newly detected. Therefore, the train rescheduling orders and speed control orders can be adjusted according to the real-time situation to guarantee effectiveness. The rolling horizon approach is terminated automatically once the disruption ends. Finally, based on the practical data of the Beijing-Tianjin intercity high-speed railway line, numerical experiments are carried out to test the effectiveness and efficiency of the proposed approach.

Dynamic areas strategy design for variable speed limiting at fixed freeway bottlenecks

Variable speed limit (VSL) control of freeway traffic is expected to improve traffic mobility and safety, especially at bottlenecks. However, unstable input flow makes the VSL less effective when the number of speed limit areas is fixed. In this paper, we first analyze the speed limit effect of the fixed speed limit area, then strengthen the VSL control effect by changing the number of speed limit areas, and finally propose a dynamic speed limit area strategy. This strategy redefines the speed limit areas and divides them into three types: normally open speed limit area, auxiliary speed limit area, and buffer speed limit area, which takes into account the transmission capability of the road and alleviates the speed difference. The effects of the VSL control strategy are evaluated using a cell transmission model. The proposed strategy uses the predictive control method to optimize the speed limit value and the number of speed limit areas. Two scenarios that considered both stable and fluctuating traffic demands are evaluated. The results show that the dynamic speed limit areas strategy can improve the safety and efficiency of the freeway.

Biomechanical Modeling of Human–Robot Accident Scenarios: A Computational Assessment for Heavy-Payload-Capacity Robots

Exponentially growing technologies such as intelligent robots in the context of Industry 4.0 are radically changing traditional manufacturing to intelligent manufacturing with increased productivity and flexibility. Workspaces are being transformed into fully shared spaces for performing tasks during human–robot collaboration (HRC), increasing the possibility of accidents as compared to the fully restricted and partially shared workspaces. The next technological epoch of Industry 5.0 has a heavy focus on human well-being, with humans and robots operating in synergy. However, the reluctance to adopt heavy-payload-capacity robots due to safety concerns is a major hurdle. Therefore, the importance of analyzing the level of injury after impact can never be neglected for the safety of workers and for designing a collaborative environment. In this study, quasi-static and dynamic analyses of accidental scenarios during HRC are performed for medium- and low-payload-capacity robots according to the conditions given in ISO TS 15066 to assess the threshold level of injury and pain, and is subsequently extended for high speeds and heavy payloads for collaborative robots. For this purpose, accidental scenarios are simulated in ANSYS using a 3D finite element model of an adult human index finger and hand, composed of cortical bone and soft tissue. Stresses and strains in the bone and tissue, and contact forces and energy transfer during impact are studied, and contact speed limit values are estimated. It is observed that heavy-payload-capacity robots must be restricted to 80% of the speed limit of low-payload-capacity robots. Biomechanical modeling of accident scenarios offers insights and, therefore, gives confidence in the adoption of heavy-payload robots in factories of the future. The analysis allows for prediction and assessment of different hypothetical accidental scenarios in HRC involving high speeds and heavy-payload-capacity robots.

Investigation on variable speed limit control strategy of expressway under adverse weather conditions

In order to effectively improve the capacity of expressways under adverse weather conditions (rainy, foggy and snowy) and reduce the potential safety hazards of expressways, a variable speed limit control strategy is proposed. First, the impact of road alignment on traffic capacity is considered, and road traffic capacity reduction coefficients under different bends and slopes are added so that the cell transmission model and a dynamic traffic flow model can be established; Secondly, the maximum speed limit value under adverse weather conditions is determined according to the influence of rainfall intensity under rainy weather conditions, visibility under foggy weather conditions, and road adhesion coefficient under snowy weather conditions on traffic capacity; Finally, an adaptive genetic algorithm is employed to solve the function that satisfies the safety and efficiency of traffic operation. The results show that the variable speed limit control strategy under adverse weather conditions effectively improves the road capacity, reduces the driving risk of vehicles, and alleviates traffic congestion.

Research progress on train operation safety in Xinjiang railway under wind environment

Abstract Railway lines in the Xinjiang wind area face severe wind disasters year-round, which seriously affects the safety and economy of the railway in China. Therefore, the wind characteristics and statistics of wind-induced accidents along the Xinjiang railway lines are presented and the basic research route for evaluating the train running safety under crosswinds and effective measures to improve the windproof performances of trains are proposed, which are meaningful to deal with wind-induced train accidents. Based on this research route, a series of numerical simulations are conducted to evaluate train safety and the corresponding measures are provided. The results show the following. The running safety of the train under crosswinds mainly depends on the aerodynamic loads acting on the train. The relationships between the safe speed limit and train type, the load weight, the embankment height, the road cutting depth, the railway line curve parameters, the yaw angle and other factors are obtained. The critical wind-vehicle speed relationship, as well as the engineering speed limit value under different running conditions, are determined. Large values of the aerodynamic and dynamic indices mainly appear in special locations, such as near earth-embankment-type windbreak walls, shallow cuttings and the transition sections between various types of windbreak walls. Measures such as increasing the height of the earth-embankment-type windbreak walls, adding wind barriers with reasonable heights in shallow cuttings and optimizing the design of different types of transition sections are proposed to significantly improve the safe speed limits of trains under crosswinds.

Adopting a Safe System Approach to Determine Safer Speed Limits: A Case Study from Iran

Speed management is one of the main dimensions of the Safe System Approach for reducing both the risk of crash involvement as well as injury severity. This study proposes a practical framework for setting safer speed limits on duplicated rural highways that has been applied to six pilot corridors (total carriageway length of approximately 1,250 km) in Iran. The safer speed limits determined from the proposed framework have been compared with the currently posted speed limits using several indicators and showed a considerable reduction in the total number of changes in speed limits while having very limited impact on reducing the mean travel speed and increase travel time along the study corridors. The study of the pilot corridors establishes that a clear approach and documented guidelines for setting speed limits provides a basis for quantifying engineering judgments about road hazards and determining more consistent speed limit values for similar conditions across Iran’s rural highway network, legitimising speed limit reductions aimed at saving lives.

Speed limits and accident rates on highways around the world, is there a correlation?

The objective of this study stands for the investigation and evaluation of accidents that take place on highways, in comparison with speed limits. The main body of this research is based on the collection of highways speed limits from different countries around the globe regarding to years, 2010, 2017 and 2018. Secondly, accident rates are collected from highway authorities, as well as from international literature. Subsequently, a statistical analysis of the collected data is conducted and finally leads to an equation that links and correlates the speed limit values and the number of accidents. The results of this statistical analysis show that speed limit plays a certain and distinctive role in the accident rate value. However, one of the interesting findings, stands for the non-continuously increasing number of accidents in the speed limit range, from the lowest to the highest value, meaning that there is an inflection point in the graph of the correlation equation. To be noted, that in terms of this study, the aforementioned correlation is independent of other factors that could affect the accident rate, such as vehicles condition, technology, road network length and condition.

Comprehensive Operation Risk Assessment of a Highway Maintenance Area Based on Reliability

To study the influence of various working conditions on traffic safety in the maintenance area of a mountain expressway, 675 groups of PTV VISSIM traffic simulation experiments were designed with various traffic organization modes, traffic volumes, traffic compositions, activity area lengths, and speed limit values. The results show that the activity area length of a closed lane, a compressed lane, and a borrowed opposite lane had no marked influence on the traffic conflicts. There was a significant positive correlation between the proportion of trucks and the number of traffic conflicts, and the number of traffic conflicts increased significantly with an increase in traffic volume. In the closed lane and borrowed opposite lane scenarios, the increase in traffic conflicts was more obvious with the increase in traffic volume. There were obvious differences in the number of traffic conflicts under different forms of traffic organization. The number of conflicts in the compressed lane scenario was the lowest, and in the borrowed opposite lane scenario the number of conflicts was the highest. There was a significant correlation between a decrease in the speed limit and an increase in the number of traffic conflicts. Finally, with traffic volume, truck proportion, and speed limit values as independent variables and reliability as a dependent variable, linear regression equations of reliability were established for three traffic organization scenarios: closed lane, borrowed opposite lane, and compressed lane.

Correlation between visibility and traffic safety visual distance in foggy areas during the daytime

Objective Traffic safety is closely related to the driver's ability to obtain visual information. Low visibility would result in traffic accidents. This study aimed to explore the difference between meteorological visibility and traffic safety visual distance in foggy areas in the daytime, and analyze the difference between dynamic visual ability and static visual ability, so as to calculate the maximum acceptable speed limit that meets the driver's safety visual distance requirement. Methods Visual distances under different visibility conditions were collected for 12 passenger car drivers through static and naturalistic driving visual recognition experiments. The power function relation model between driver's static visual distance and meteorological visibility was established, and the attenuation rates of dynamic visual distance at different driving speeds were obtained. Results Traffic safety visual distance (TSVD) gradually grows with the increase of visibility and finally tends to be stable due to the vision limitation of the human eyes under good weather conditions. The drivers' visual ability decreased while driving dynamically, and dynamic TSVD was shorter than static TSVD. Conclusions Traditional meteorological visibility is different from drivers' actual TSVD, but there is a correlation between them. According to the relationship between visibility and dynamic TSVD, the maximum recommended speed limit values under different visibility levels are provided. The calculation of the maximum acceptable speeds under specific visibility conditions can provide a technical basis for road construction and traffic management.

Sistem Pendeteksi Kecelakaan Kendaraan Bermotor Menggunakan Arduino Dan Smartphone Android

Abstract - Many motor vehicle accidents occur in Indonesia. One of the factors causing the high number of accidents is the large number of motorized vehicle users. Accident reporting is currently still hampered by reporting. This research creates an accident reporting system that is fast and automatic to a web server. This study aims to create a system that can report accident locations. Next, the preparation of the machine condition status detection device. And the web server receives the coordinates of the crash site. This system combines an android smart phone with an Arduino microcontroller. In this research, the voltage sensor is used to overcome the motor vehicle battery voltage. Machine condition data transmission status from device to android smart phone using bluetooth HC-05. Accelerometer and GPS sensors on android smartphones are used to check acceleration and location coordinates during an accident. This study uses 4 vehicle conditions while moving. Vehicle traveling normally, sudden brake, front collision and side collision. The speed limit value used in this study is 19.04 m / s2 or 1.94 g. Based on the research results, when the vehicle is running normally there is no significant change in the value of acceleration. In a sudden brake condition, the Y axis of the acceleration sensor decreases in value until the acceleration value is negative. In the hit-front condition, the Y-axis value has increased significantly. Meanwhile, in a side hit condition, the value of the X and Y axes has increased significantly. The front and side crash conditions were tested 10 times each. Front hit conditions were identified as accidents by 80%. While the side hit condition was identified as an accident as much as 100%.
 Keywords: sensor, accelerometer, accident, GPS, Android smart phone.

Reasonable driving speed limits based on recognition time in a dynamic low-visibility environment related to fog—A driving simulator study

To determine a reasonable speed limit and ensure traffic safety in a dynamic low-visibility environment with fog, a driving simulator study was conducted. A total of 31 young participants were recruited, and each completed 5 driving simulator trials under varying visibility conditions and speed levels during the daytime. The combined coupling effect of the visibility and driving speed on drivers’ recognition times was explored, and a quantitative model of the recognition time, visibility, and driving speed was established. A determination method and suggested value of a reasonable driving speed limit in dynamic low-visibility conditions were proposed based on the stopping sight distance model. The results show that there are significant differences in the recognition times of drivers under different visibility and speed conditions. The reasonable driving speed limit values in dynamic low-visibility conditions should be based on visibility changes. When the stopping sight distance is 75 m and the visibility is less than 35 m, the speed limit should be 20 km/h. When the visibility is between 35 m and 60 m, the speed limit should be 30 km/h. When the visibility is between 60 m and 140 m, the speed limit should be 50 km/h. When the visibility is greater than 140 m, the speed limit should be 60 km/h. These research results can provide a theoretical reference for the formulation of a VSL in a dynamic low-visibility environment related to fog and reduce crash risk in conditions of inadequate visibility in fog.

The Speed Limit Determination of Tunnel Entrance And Exit Section On Rainy Days

In order to reduce the number of traffic accidents caused by rainy days on the entrance and exit sections of tunnels, a reasonable speed limit value on the entrance and exit sections of tunnels is proposed to improve the safety of vehicles on these sections. This paper takes passenger cars as the research object, and by exploring the changes of road friction coefficient and visibility in rainy weather, the driving environment parameters under different rainfall intensity are clarified. Taking the visible distance of the driver and the critical state of vehicle sideslip as safety indexes, the speed limit value of the section outside the tunnel in rainy days is obtained, and the allowable speed of the section inside the tunnel is determined by taking the continuity of the running speed as the standard. The study shows that the speed limit value of the tunnel entrance and exit section in rainy days takes visibility as the main limit index and decreases with the increase of rainfall intensity. When the rainfall intensity is greater than 1.5mm/min, the speed limit of the tunnel section is needed.

Study on the Speed Limit at Night in Expressway Maintenance Area

In order to improve the safety of expressway maintenance work area at night, taking the maintenance work area of two-way four lane Expressway in Anhui Province as an example, the traffic characteristics of the maintenance work area at night are analysed, and the variation characteristics of vehicle speed in the maintenance work area are studied, and the main factors affecting traffic safety are obtained. Based on the traffic flow theory and Greenshields speed density-linear relationship model, this paper analyses the correlation between the speed and traffic capacity in the maintenance work area. Through the simulation by VISSIM software, the speed limit value of the expressway maintenance work area in the day and night is obtained, which provides an important reference value for the expressway maintenance operation.

Study on the Distribution Law and Speed Limit of Night Speed in Expressway Maintenance Area

In order to reasonably determine the maximum and minimum vehicle speed limit values at night and ensure the driving safety in the maintenance area of expressway, the distribution law of vehicle speed at night in the maintenance area of expressway is studied. Based on the investigation of one-way lane closure construction in the four-lane maintenance area of expressway, the location speed of the main traffic control area in the night maintenance area is analyzed, and the average speed, 85% vehicle speed, the speed difference in different areas and the speed difference in heavy-duty vehicle(HDV) and light-duty vehicle(LDV) workshops are determined. The results show that the standard deviation of vehicle speed distribution from warning area to transition zone to construction area is obviously reduced, and the speed difference between HDV and LDV is also obviously reduced. Finally, according to the distribution characteristics of night speed, the night speed limit model of maintenance operation area is given, the speed limit values of different models are calculated respectively, and the night perceived speed model is used to modify the speed limit value.

Factors affecting lane change crashes

This study aims to investigate the contributing factors affecting the occurrence of crashes while lane-changing maneuvers of drivers. Two different data sets were used from the same drivers' population. The first data set was collected from the traffic police crash reports and the second data set was collected through a questionnaire survey that was conducted among 429 drivers. Two different logistic regression models were developed by employing the two sets of the collected data. The results of the crash occurrence model showed that the drivers' factors (gender, nationality and years of experience in driving), location and surrounding condition factors (non-junction locations, light and road surface conditions) and roads feature (road type, number of lanes and speed limit value) are the significant variables that affected the occurrence of lane-change crashes. About 57.2% of the survey responders committed that different sources of distractions were the main reason for their sudden or unsafe lane change including 21.2% was due to mobile usage. The drivers' behavior model results showed that drivers who did sudden lane change are more likely to be involved in traffic crashes with 2.53 times than others. The drivers who look towards the side mirrors and who look out the windows before lane-change intention have less probability to be involved in crashes by 4.61 and 3.85 times than others, respectively. Another interesting finding is that drivers who reported that they received enough training about safe lane change maneuvering during issuing the driving licenses are less likely to be involved in crashes by 2.06 times than other drivers.

Study on the Capacity of Urban Road Construction Section under Mixed Traffic Environment

Based on the analysis of the calculation model of the capacity of urban road construction section, a calculation optimization model considering the influence of non-motor vehicle factors on the capacity of construction section is established. Through the recording and calibration of the geometric and traffic parameters of the construction section at the intersection of Huangshan Road and Susong Road in Hefei City, and using PTV-VISSIM10 for modeling and calculation, the calculation model of non-motor vehicle reduction factor is constructed. Finally, the optimization model of the capacity of the construction section is verified by combining with observation data of the morning peak of the urban road construction section under mixed traffic environment. The results show that the relative error between the calculated value of the capacity and the observed value of the construction section under mixed traffic environment is less than 5%. Therefore, it is reasonable to consider the non-motor vehicle reduction factor on the capacity calculation model of the construction section, and make up for the original model to only consider the insufficient factors such as the proportion of the large vehicle, length of work area and speed limit value.

Speeding behavior and speed limits for heterogeneous bicycle flow

Objective: Speed limits for motorized vehicles are widely used to reduce noise and promote road safety. Unfortunately, there is little research on speed limits for bicycles, especially for electric bicycles. This article aims to analyze the speeding behavior and propose the suggested speed limit values for electric bicycles.Methods: Field speed data were collected from 11 segments of separated bicycle lanes in Hangzhou, China. The speeding behavior of different types of bicycles was analyzed under different speed limits. Mixed logistic models are proposed to model speeding behavior and its influencing factors. Eighty-fifth percentile speeds under different conditions were calculated as speed limits. Stepwise regression models are proposed to model the relationships between the 85th percentile speeds and their influencing factors, and speed limits for different types of bicycles were determined.Results: It is recommended that the speed limits for pure electric bicycle traffic be set as 25–30 km/h and 30–35 km/h for bicycle lanes with widths less than 3 m and greater than 3 m, respectively. The recommended speed limit for heterogeneous bicycle flows is 25 km/h.Conclusions: The suggested speed limit values for different bicycle traffic flow can help to improve speed limit laws and policies for bicycle traffic.