Varying Vehicle Speed Research Articles

Solving the large‐scale min–max K‐rural postman problem for snow plowing

This article studies the snow plow routing problem, which is a modified version of the min–max problem with k‐vehicles for arc routing on a mixed graph with hierarchy. Each arc or edge is given a priority and instead of minimizing the overall finishing time, we minimize the latest finishing time for each priority class. We consider turn restrictions, route balancing, and variable vehicle speeds in a real large‐scale network. To solve the problem, we present a graph transformation from a directed rural postman problem with turn penalties to an asymmetric traveling salesman problem. We then make the following modifications to the metaheuristics to better handle the constraints: development of new neighborhood operators, several applications of the same destruction operators before repair of the solution, and a dynamic arc‐grouping procedure when links are removed or inserted. We tested our methodology on three real networks with 1,626 to 2,146 street segments and 613 to 723 intersections. The results show that our approach can improve the solution, and the grouping procedure is helpful. The results also show that some operators perform better than others; the network topology seems to explain these variations. Finally, we validated our methodology by comparing to some routes planned in the past and to some routes obtained from a commercial solver. © 2017 Wiley Periodicals, Inc. NETWORKS, Vol. 70(3), 195–215 2017

Development of a real-time prediction model of driver behavior at intersections using kinematic time series data

As connected autonomous vehicles (CAVs) enter the fleet, there will be a long period when these vehicles will have to interact with human drivers. One of the challenges for CAVs is that human drivers do not communicate their decisions well. Fortunately, the kinematic behavior of a human-driven vehicle may be a good predictor of driver intent within a short time frame. We analyzed the kinematic time series data (e.g., speed) for a set of drivers making left turns at intersections to predict whether the driver would stop before executing the turn. We used principal components analysis (PCA) to generate independent dimensions that explain the variation in vehicle speed before a turn. These dimensions remained relatively consistent throughout the maneuver, allowing us to compute independent scores on these dimensions for different time windows throughout the approach to the intersection. We then linked these PCA scores to whether a driver would stop before executing a left turn using the random intercept Bayesian additive regression trees. Five more road and observable vehicle characteristics were included to enhance prediction. Our model achieved an area under the receiver operating characteristic curve (AUC) of 0.84 at 94m away from the center of an intersection and steadily increased to 0.90 by 46m away from the center of an intersection.

Wheel nominal rolling radius difference on hunting stability of railway vehicle system under a speed-dependent nonlinear creep model

This study presents the hunting stability of a railway vehicle system in a speed-dependent nonlinear creep model with varying wheel conicity and nominal rolling radius. Integrating Kalker’s linear theory, Hertz contact theory, and the heuristic nonlinear creep model, the speed-dependent nonlinear creep model, including the semi-axis lengths and nonconstant creep coefficients with the varying vehicle speed, is investigated. Modeling and dynamic analysis are performed in the 28 degrees-of-freedom railway vehicle system. Lyapunov’s indirect method is used to calculate critical hunting speed of a railway vehicle system. The effects of suspension system parameters, various wheel conicities, and nominal rolling radii on the hunting stability are illustrated and compared. Critical hunting speeds calculated for the original design wheel are consistently better than those obtained from worn wheels with differences in wheel conicity and wheel rolling radius. Notably, critical hunting speeds calculated for a softer stiffness and damping decrease as wheel nominal rolling radius difference increases. Furthermore, the critical hunting speed calculated by the harder stiffness and damping increase as wheel nominal rolling radius difference increases. Analysis of hunting stability further shows that vehicle running speed must be considered when the wheel nominal rolling radius is less than the origin design wheel radius. Therefore, the effects of various wheel nominal rolling radius differences on hunting stability is an important research issue.

Curvature-Based Ground Vehicle Control of Trailer Path Following Considering Sideslip and Limited Steering Actuation

In this paper, a curvature-based control method capable of both forward and backward path following is developed for off-axle hitching trailers. Compared with earlier methods, this controller handles varying path curvature better while also being easy to implement and tune. The controller also addresses two major issues that deteriorate tracking accuracy: limited steering actuation and sideslip. An active speed limiter brakes the vehicle when the steering angle error is too high and therefore allows the same set of control gains to work across a relatively large range of reference speeds without significantly increasing lateral error or losing stability, which further simplifies controller tuning. An extended Kalman filter (EKF) sideslip estimator is designed to allow sideslip compensation, which considers the varying noise magnitude in GPS measurements caused by varying vehicle speeds so that the braking maneuver will not significantly deteriorate the estimations. To our knowledge, this paper presents the first publication of these two algorithms with trailer control. This method is compared with results from two earlier hitch-angle-based control methods in simulation and experiment. The active speed limiter and the EKF are also implemented on these control methods for fair comparison, during which it is found that the two algorithms can directly work with other control methods and benefit their performance. The results show the curvature-based controller provides better maneuverability and reduced tracking error.

Influences Analysis of In-wheel Motor on EV Vibration Performance

To analyse the influence of the increased unsprung mass on electric vehicle vibration performance as in-wheel motor embedded within the hub, Using one-quarter vehicle system with two degree-of-freedom, the vibration model of in-wheel motor electric vehicle is established, and the vibration performance indexes are presented. The frequency response characteristics and statistical characteristics of vibration response quantity are built by the method of frequency domain analysis. The influence of the increased unsprung mass on the vibration performance of electric vehicle is analysed based on B-level road and urban driving condition. The results show that vehicle speed variation has greater impact on the vibration response varibles of in-wheel motor electric vehicle; and the increased unsprung mass of in-wheel motor electric vehicle exerts a little influence on body acceleration and wheel displacement, but has a serious impact on wheel acceleration and an evident influence on relative dynamic load of wheel, as well as a certain influence on suspension deflection.

A Practical Animal Detection and Collision Avoidance System Using Computer Vision Technique

One serious problem that all the developed nations are facing today is death and injuries due to road accidents. The collision of an animal with the vehicle on the highway is one such big issue, which leads to such road accidents. In this paper, a simple and a low-cost approach for automatic animal detection on highways for preventing animal-vehicle collision using computer vision techniques are proposed. A method for finding the distance of the animal in real-world units from the camera mounted vehicle is also proposed. The proposed system is trained on more than 2200 images consisting of positive and negatives images and tested on various video clips of animals on highways with varying vehicle speed. As per the two-second rule, our proposed method can alert the driver when the vehicle speed is up to 35 km/h. Beyond this speed, though the animal gets detected correctly, the driver does not get enough time to prevent a collision. An overall accuracy of almost 82.5% is achieved regarding detection using our proposed method.

Ground vibrations induced by InterCity/InterRegion trains: a numerical prediction based on the multibody/finite element modeling approach

This present paper aims to identify the main components which influence the generation and the propagation mechanisms of railway-induced ground vibrations. It is based on numerical assessments of ground vibrations on the L161 line that runs through Brussels Capital Region, Belgium. The objective is twofold. First, using data collection at a Brussels site, a numerical prediction model is built up. It is based on a two-step approach, recently validated in tramway and high-speed train cases and improved by an accurate description of the foundation. The vehicle/track/foundation and soil subsystems are treated successively. A key advantage of the new approach is that it is capable of including the effect of soil conditions in the vehicle/track simulation. The vehicle is modeled with the help of the multibody strategy. The soil is a three-dimensional finite/infinite element model, with a complex geometry on the surface and inclined soil layers. The track model includes a rail joint defect. The model is eventually validated against experimental data. Then, a sensitivity analysis on parameters of the studied site is performed. The vehicle and foundation modeling are discussed, along with the influence of local defects and vehicle speed variation on ground vibrations.

Urban Expressway Functional Reliability

AbstractDifferent grades of roads have different function goals during the process of planning and design. The extent of function realization has significant effects on the operational efficiency of a road network system. In accordance with the function description of urban expressways in the Code for Design of Urban Road Engineering (CJJ37—2012), this study presents the concept of urban expressway functional reliability. This concept is also considered as a quantitative and probability evaluation index of the achievement degree of expressway functions. The calculation method of expressway functional reliability is constructed by combining vehicle speed with the coefficient of headway variation. The similarities and differences between the level of service and the proposed function reliability are discussed. Three expressway sections in Zhengzhou city are taken as case studies. The independence between vehicle speed and headway variation coefficient is verified based on the real data collected through vid...

Exposure and inequality for select urban air pollutants in the Tampa Bay area

Air pollution exposure has been linked to numerous adverse health effects, with some disadvantaged subgroups disproportionately burdened. The objective of this work was to characterize distributions of emissions and concentrations of a few important urban air toxics at high spatiotemporal resolution in order to assess exposure and inequality. Benzene, 1,3-butadiene, formaldehyde, and acetaldehyde were the focus pollutants, with oxides of nitrogen (NOx) estimated for comparisons. Primary pollutant emissions were estimated for the full spectrum of source types in the Tampa area using a hybrid approach that is most detailed for major roadways and includes hourly variations in vehicle speed. Resultant pollutant concentrations were calculated using the CALPUFF dispersion model, and combined with CMAQ model output to account for secondary formation of formaldehyde and acetaldehyde. Census demographic data were applied to estimate residential pollution exposures and inequality among population subgroups. Estimated concentrations of benzene, 1,3-butadiene, and NOx were generally higher in urban areas and lower in rural areas. Exposures to these pollutants were disproportionately high for subgroups characterized as black, Hispanic and low income (annual household income less than $20,000). For formaldehyde and acetaldehyde, the patterns of concentration and exposure were largely reversed. Results suggest that disparities in exposure depend on pollutant type.

Vehicle-to-Vehicle Forwarding in Green Roadside Infrastructure

Smart scheduling can be used to reduce infrastructure-to-vehicle energy costs in delay-tolerant vehicular networks. In this paper, we show that, by combining this with vehicle-to-vehicle (V2V) forwarding, downlink (DL) traffic schedules can be generated, whose energy costs are lower than that in the single-hop case. This is accomplished by having the roadside units (RSUs) dynamically forward packets through vehicles, which are in energy-favorable locations. This paper considers both constant bit rate (CBR) and variable bit rate (VBR) air-interface options. We first derive offline schedulers for the DL RSU energy usage when V2V forwarding is added to RSU-to-vehicle communication. Both in-channel and off-channel forwarding cases are considered. The CBR and VBR cases are obtained using integer linear programming (ILP) and time-expanded graph (TEG) formulations, respectively. These schedulers provide lower bounds on energy performance and are used for comparisons with a variety of proposed online scheduling algorithms. The first algorithm is based on a greedy local optimization (GLOA). A version of this algorithm, which uses a minimum-cost flow graph (MCFG) scheduler, is also introduced. A more sophisticated algorithm is then proposed, which is based on a finite-window group optimization (FWGO). Results from various experiments show that the proposed algorithms can generate traffic schedules with much improved DL energy requirements compared with the case where V2V packet forwarding is not used. The performance improvements are particularly strong when under heavy loading conditions and when the variation in vehicle communication requirements or vehicle speed is high. Results that compare the proposed algorithms with conventional nonenergy-aware schedulers are also presented.

Experimental validation and robustness analysis of a multiple model switching antilock braking system control algorithm

In this paper, antilock braking system (ABS) control algorithms based on multiple model switching lead lag controllers are designed and are experimentally validated. Algorithms are designed to be adaptive with changing driving and road conditions in a switched multiple model manner. The effectiveness of the switching controllers is evaluated during transitions between different road friction coefficients. As the structure of the original experimental test device did not allow for the dynamic modification of the friction coefficient, controller switching stability was demonstrated under varying normal wheel load conditions implemented through simple modifications made on the test setup. The performance of the proposed controllers against varying vehicle speed and friction was also evaluated through simulations involving a half car braking model where a combined multiple model controller and observer structure was implemented. Experimental and simulation results indicate that the proposed control method is a potential candidate for implementation on a test vehicle.

Examination of the Free-Flow Speed Distribution on Two-Lane Rural Roads

Free-flow speed variation of passenger vehicles along a road segment is one of the most used factors in road safety studies, as a surrogate measure to evaluate road design consistency. Free-flow speed may be measured when a road segment is already built but must be estimated during the design phase. Several studies have been carried out to calibrate models to estimate free-flow speed, with geometric features as explanatory variables. Currently, most free-flow speed models focus only on mean speed or speed in particular percentiles, such as the 85th or 95th. Moreover, most studies have assumed normality in the free-flow speed distribution without checking this hypothesis. The main objective of this study was to analyze the free-flow speed distribution on two-lane rural road curves and tangents. The research focused on two main issues: determining whether speed data were normally distributed at a specific site and analyzing the behavior of the mean and standard deviation of speed on curves and tangents. The study was based on continuous operating speed profiles, which were obtained from a database of more than 16,000 vehicles/km. A total of 63 horizontal curves and 78 tangents were analyzed. According to the results, the normal distribution is not the best distribution in most cases for describing free-flow speeds. In 46 of the curves and 64 of the tangents, free-flow speed cannot be assumed to be normally distributed. Therefore, some other distributions should be tested in further research.

USING ROAD TEST FOR INSPECTION OF AN AUTOMOTIVE ENGINE

The engine power could be measured accurately using an engine dynamometer but this process is time and money consuming due to difficulty of coupling the engine to the dynamometer. The coupling process can be eliminated using chassis dynamometer. Hence the chassis dynamometer is a road resistance simulator. Why not to take the actual road as the source of resistance instead of using chassis dynamometer? This process will be faster and cheaper taking less than a minute on road for a single test and will help to detect the condition of the engine and power train easily. The aim of this paper is to evaluate the use of the road as a source of resistance for the calculation of engine power. Nowadays, there are many software products that claim the possibility to measure the engine power on road. In our study road tests have been performed using OBD (On Board Diagnostic System) reader devices and high-speed GPS (Global Positioning System) receiver to measure vehicle speed variation with time during acceleration process. Three different vehicles are used to validate the road tests obtained data using chassis dynamometer. The proposed method proved its ability of using road test during automotive engine inspection process. Based on the validation the OBD and GPS data shows a difference between both methods by ±2% .

Using a Virtual Environment to Examine How Children Cross Streets: Advancing Our Understanding of How Injury Risk Arises.

To examine how risk of injury can arise for child pedestrians. Using a highly immersive virtual reality system interfaced with a 3-D movement measurement system, younger (M = 8 years) and older (M = 10 years) children's crossing behaviors were measured under conditions that introduced variation in vehicle speed, distance, and intervehicle gaps. Children used distance cues in deciding when to cross; there were no age or sex differences. This increased risk of injury in larger intervehicle gaps because they started late and did not monitor traffic or adjust walking speed as they crossed. In contrast, injury risk in smaller intervehicle gaps of equal risk (i.e., same time to contact) occurred because crossing behavioral adjustments (starting early, increasing walking speed while crossing) were not sufficient. Dependence on distance cues increases children's risk of injury as pedestrians when crossing in a variety of traffic situations.

Interval observer design for LPV systems with parametric uncertainty

Observer design for dynamical systems with both known and unknown time-varying parameters is of significant interest in a number of real-world applications. This class of systems has been rarely addressed in the existing literature. This paper develops an interval observer design methodology for linear parameter varying (LPV) systems with parametric uncertainty. With information on upper and lower bounds of the uncertain parameters, an interval observer that produces an envelope covering all possible state trajectories is presented. The application of the proposed algorithm in an important vehicle state estimation problem which aims at minimizing the worst-case envelope of the side-slip-angle estimate in the presence of uncertain tire cornering stiffness parameters and varying vehicle speed is presented. The obtained observer is evaluated in simulation using CarSim, a commercial industry-standard vehicle simulation software. The results verify the value of the developed observer design method.

Mixed Traffic Speed–Flow Behavior under Influence of Road Side Friction and Non-Motorized Vehicles: A Comparative Study of Arterial Roads in India

Abstract—Present study is carried out on six lane divided urban arterial road in Patna and Pune city of India. Both the road having distinct differences in terms of the vehicle composition and the road side parking. Arterial road in Patan city has 33% of non-motorized mode, whereas Pune arterial road dominated by 65% of Two wheeler. Also road side parking is observed in Patna city. The field studies using videography techniques are carried out for traffic data collection. Data are extracted for one minute duration for vehicle composition, speed variation and flow rate on selected arterial road of the two cities. Speed flow relationship is developed and capacity is determine. Equivalency factor in terms of dynamic car unit is determine to represent the vehicle is single unit. The variation in the capacity due to side friction, presence of non motorized traffic and effective utilization of lane width is compared at concluding remarks.

Overhead Pedestrian Crossings – Economic Evaluation through Vehicle Operating Cost and Travel Time Savings

At-grade road crossing facility presently available at the main entrance to the Sri Lanka Institute of Information Technology (SLIIT) Malabe can be improved as a solution to minimize the disturbance of traffic flow along Malabe - Kaduwela road. It is observed that a large number of students cross the road throughout the day, especially during the peak of traffic. Several other reasons for this traffic congestion were identified, such as; unruliness of pedestrians, violation of traffic rules by drivers (especially bus drivers who stop buses everywhere although there are properly located bus stops), inadequate road width etc. Due to the above reasons, vehicles traveling along this stretch of road have to constantly slow down and then regain their original speed after passing the location. Introduction of an overhead pedestrians’ crossing at the location would separate pedestrians from traffic to minimize the vehicle - pedestrian conflict to create a uniform traffic flow along the road section. Hence, by minimizing the sudden speed variation of vehicles (speed change cycle) due to the existing pedestrians crossing the road, the additional Vehicle Operating Cost (VOC), additional travel time and risk for pedestrians when crossing the road, as well as uncomfortable driving condition for drivers can be reduced. The objective of this study is to minimize the additional VOC and travel time due to sudden speed variation at this existing pedestrian crossing by improving the traffic flow condition. Therefore, an overhead pedestrian crossing with the view of facilitating the pedestrians to cross the road comfortably and safely is proposed. The proposed structure has a clear height of 5.5 m and 18 m of span. Two flights of steps of one meter width were designed for both ends of the overhead bridge as access. Total cost for the proposed structure was computed for the year of 2012. Further the additional cost for the VOC and travel time per day were analyzed and predicted for a period of 20 years from the year 2012. After having determined the costs and benefits of the project, a method was evolved for relating these two so as to arrive at the assessment of the viability of the project in economic terms. Among a number of methods developed for such an economic evaluation, Internal Rate of Return (IRR) method was justified and selected. DOI: http://dx.doi.org/10.4038/ouslj.v7i0.7309 OUSL Journal Vol.7 2014: 77-94

Field monitoring of a bridge using digital image correlation

In order to provide quantitative data to supplement visual inspections and numerical modelling as part of the overall bridge assessment process, inexpensive sensor technologies that provide useful and accurate data are required. Digital image correlation (DIC) is a measurement technique that can be used to provide displacement, crack width and strain data from the same set of digital images. This paper outlines a field application using DIC to measure static displacements at varying load levels and dynamic displacements at varying vehicle speeds of a reinforced concrete bridge. The DIC displacement measurements provided by two different camera systems are shown to be in good agreement with the results from a conventional displacement transducer for both the static and the dynamic tests. The results of the static tests with varying load levels are then used to illustrate how the bridge response can be evaluated by examining the load deflection behaviour, which remained in the linear elastic range throughout the loading. The dynamic displacement data were then compared to the static response to determine what, if any, difference in response there was to dynamic loading and thus if the use of impact factors should be considered when assessing this bridge.

Evolutionary algorithm-based PID controller tuning for nonlinear quarter-car electrohydraulic vehicle suspensions

The basic challenge associated with the design of vehicle suspension system is the attainment of an optimal trade-off between the various design objectives. This study presents the design of proportional-integral-derivative (PID) controller for a quarter-car active vehicle suspension system (AVSS) using evolutionary algorithms (EA) such as the particle swarm optimization (PSO), genetic algorithm (GA) and differential evolution (DE). Each of the EA-based PID controllers showed overall improvement in suspension travel, ride comfort, settling time and road holding from the manually tuned controller and the passive vehicle suspension system. These improvements were, however, achieved at the cost of increased actuator force, power consumption and spool-valve displacement. DE-optimized PID control resulted in the best minimized suspension performance, followed by the GA and PSO, respectively. Frequency-domain analysis showed that all the signals were attenuated within the whole body vibration frequency range and the EA-optimized controllers had RMS frequency weighted body acceleration of the vehicle within allowable limits for vibration exposure. Robustness analysis of the DE-optimized PID-controlled AVSS to model uncertainties is carried out in the form of variation in vehicle sprung mass loading, tyre stiffness and speed.

A vehicle re-identification algorithm based on multi-sensor correlation

Magnetic sensors can be applied in vehicle recognition. Most of the existing vehicle recognition algorithms use one sensor node to measure a vehicle‖s signature. However, vehicle speed variation and environmental disturbances usually cause errors during such a process. In this paper we propose a method using multiple sensor nodes to accomplish vehicle recognition. Based on the matching result of one vehicle‖s signature obtained by different nodes, this method determines vehicle status and corrects signature segmentation. The co-relationship between signatures is also obtained, and the time offset is corrected by such a co-relationship. The corrected signatures are fused via maximum likelihood estimation, so as to obtain more accurate vehicle signatures. Examples show that the proposed algorithm can provide input parameters with higher accuracy. It improves the average accuracy of vehicle recognition from 94.0% to 96.1%, and especially the bus recognition accuracy from 77.6% to 92.8%.