scholarly journals Permitted speed decision of single-unit trucks with emergency braking maneuver on horizontal curves under rainy weather

PLoS ONE ◽  
2021 ◽  
Vol 16 (12) ◽  
pp. e0261975
Author(s):  
Menghua Yan ◽  
Jinliang Xu ◽  
Shuo Han ◽  
Tian Xin ◽  
Ouyu Wang ◽  
...  
Keyword(s):  
Single Unit ◽  
Water Film ◽  
Vehicle Speed ◽  
Lateral Instability ◽  
Quartic Equation ◽  
Horizontal Curves ◽  
Rainy Weather ◽  
Adverse Weather ◽  
Road Friction ◽  
Lateral Friction

Under adverse weather conditions, visibility and the available pavement friction are reduced. The improper selection of speed on curved road sections leads to an unreasonable distribution of longitudinal and lateral friction, which is likely to cause rear-end collisions and lateral instability accidents. This study considers the combined braking and turning maneuvers to obtain the permitted vehicle speed under rainy conditions. First, a braking distance computation model was established by simplifying the relationship curve between brake pedal force, vehicle braking deceleration, and braking time. Different from the visibility commonly used in the meteorological field, this paper defines "driver’s sight distance based on real road scenarios" as a threshold to measure the longitudinal safety of the vehicle. Furthermore, the lateral friction and rollover margin is defined to characterize the vehicle’s lateral stability. The corresponding relationship between rainfall intensity-water film thickness-road friction is established to better predict the safe speed based on the information issued by the weather station. It should be noted that since the road friction factor of the wet pavement not only determined the safe vehicle speed but also be determined by the vehicle speed, so we adopt Ferrari’s method to solve the quartic equation about permitted vehicle speed. Finally, the braking and turning maneuvers are considered comprehensively based on the principle of friction ellipse. The results of the TruckSim simulation show that for a single-unit truck, running at the computed permitted speed, both lateral and longitudinal stability meet the requirements. The proposed permitted vehicle speed model on horizontal curves can provide driving guidance for drivers on curves under rainy weather or as a decision-making basis for road managers.

Steering Strategy for a Multi-Axle Wheeled Vehicles

2018 ◽  
Author(s):  
Waqar Ahmed ◽  
Raja Amer Azim ◽  
Sana Fatima
Keyword(s):  
Mathematical Model ◽  
Single Unit ◽  
Steering System ◽  
Vehicle Speed ◽  
Wheel Slip ◽  
Turn Radius ◽  
Heavy Loads ◽  
The Mathematical Model ◽  
Wheeled Vehicles ◽  
Good Vehicle

This paper presents a mathematical model for multi-axle steering vehicles operating on level ground. For transporting heavy loads vehicles with multiple axles are required. Apart from added complexity steering of multiple axle for turning is a big challenge. Due to type of load being carried a single unit vehicle is sometimes preferred. The mathematical model of a six axle vehicle with 4-axle steering system is developed. Simulations at various track radii, vehicle speeds and steering ratios (ratio between the first, second, fifth and sixth steering axle) are performed. Axle steering angles and wheel slip angles are evaluated. The steering ratio requirements vary with vehicle speed and turn radius. A configuration is selected for better performance for a wider range. The resulting steering ratios show good vehicle maneuverability, stability and steering efficiency.

Active Front Steering LTV MPC for Varying Friction Conditions

2014 ◽  
Author(s):  
Nicola De Val ◽  
Andrea Fuso ◽  
Francesco Braghin ◽  
Edoardo Sabbioni
Keyword(s):  
Model Predictive Control ◽  
Predictive Control ◽  
Linear Time ◽  
Path Following ◽  
Vehicle Speed ◽  
Optimal Parameters ◽  
Active Front Steering ◽  
Road Friction ◽  
Nonlinear Vehicle Model ◽  
Road Friction Coefficient

The developed Active Front Steering (AFS) Linear Time Variant (LTV) Model Predictive Control (MPC) is a linear model predictive control based on linearization of the nonlinear vehicle model. A sensitivity analysis of the parameters of the controller is carried out on a simple path following test. Once the optimal parameters are found, both in terms of trajectory following and real-time performances, the LTV-MPC is used for determining the requirements for the necessary sensors (in terms of minimum obstacle distance detection) as a function of the vehicle speed. Then, the same analysis is carried out considering wet road conditions (i.e. the tyre-road friction coefficient is different from that accounted for by the controller).

scholarly journals Foraging opportunism and feeding frequency in the red-footed falcon (Falco vespertinus) in Slovakia: case study from 2017

2017 ◽  
Vol 11 (1) ◽  
pp. 31-41 ◽  
Author(s):  
Jozef Chavko ◽  
Anton Krištín
Keyword(s):  
Bird Species ◽  
Weather Conditions ◽  
Food Composition ◽  
Feeding Frequency ◽  
Adverse Weather Conditions ◽  
Rainy Weather ◽  
Adverse Weather ◽  
Negative Effect ◽  
Unfavourable Weather ◽  
Falco Vespertinus

Abstract Foraging opportunism and feeding frequency are less studied parameters of behaviour in insectivorous falcons, many of which are endangered bird species. In this short study, prey composition and feeding frequency of red-footed falcon (Falco vespertinus) nestlings were studied using the method of camera recordings during seven days in July 2017 in southwestern Slovakia. Camera recording analyses of 2–3 chicks (14–26 days old) in three nests revealed a significant preference for insects (97%, n = 305 prey items), of which the Italian locust (Calliptamus italicus) was highly predominant (54%). We also found very high average chick feeding frequency (9.9 feedings per hour, n = 29 hours 22 min of regular observations), whereby the females fed their young ones more frequently (64.9%, n = 305 feedings) than the males (35.1%). Analyses of food composition in adverse weather conditions showed that unfavourable weather had a negative effect on chick feeding frequency, and in rainy weather the males fed significantly less than the females.

Driver tolerance of lateral accelerations on horizontal curves

2010 ◽  
Vol 37 (3) ◽  
pp. 413-419 ◽  
Author(s):  
Eric D. Hildebrand ◽  
Jonathan Lewis
Keyword(s):  
Lateral Acceleration ◽  
Vehicle Speed ◽  
Design Standards ◽  
Driver Behaviour ◽  
Threshold Levels ◽  
Horizontal Curves ◽  
Unique Method ◽  
Short And Long Term ◽  
Digital Video Analysis

There are many roadways where existing horizontal curves fail to meet minimum geometric design standards for financial or geographic reasons. Advisory speeds, typically set with a ball-bank indicator, are posted on these curves to ensure that drivers are not subjected to uncomfortable levels of lateral accelerations as they negotiate the curve. The threshold levels of lateral acceleration as estimated by ball-bank indicators vary considerably between jurisdictions with many still basing their guidelines on studies dating back to the 1930s and 1940s. This study investigated present day ball-bank indicator tolerance levels by analyzing actual driver behaviour on 30 curves posted with advisory speeds in New Brunswick. A unique method of data collection involving digital video analysis enabled the development of vehicle speed profiles approaching and throughout the curves. The results indicated that drivers tolerate higher levels of discomfort as they navigate curves than currently assumed. This finding justifies raising the ball-bank indicator threshold levels used for posting advisory speeds. Inconsistencies between actual posted advisory speeds, policy guidelines, and jurisdictional implementation have also been identified. Recommendations address both short and long-term goals of updating ball-bank indicator thresholds used for signing to levels that better represent driver behaviour. Longer-term recommendations address the development of uniform signing standards across Canada so that driver expectation will not be violated between jurisdictions.

scholarly journals Risk Factors Affecting Traffic Accidents at Urban Weaving Sections: Evidence from China

2019 ◽  
Vol 16 (9) ◽  
pp. 1542 ◽  
Author(s):  
Xinhua Mao ◽  
Changwei Yuan ◽  
Jiahua Gan ◽  
Shiqing Zhang
Keyword(s):  
Risk Factors ◽  
Traffic Accidents ◽  
Multinomial Logistic Regression ◽  
Weather Condition ◽  
Weather Conditions ◽  
Traffic Density ◽  
Vehicle Speed ◽  
Factors Affecting ◽  
Traffic Characteristics ◽  
Rainy Weather

As a critical configuration of interchanges, the weaving section is inclined to be involved in more traffic accidents, which may bring about severe casualties. To identify the factors associated with traffic accidents at the weaving section, we employed the multinomial logistic regression approach to identify the correlation between six categories of risk factors (drivers’ attributes, weather conditions, traffic characteristics, driving behavior, vehicle types and temporal-spatial distribution) and four types of traffic accidents (rear-end, side wipe, collision with fixtures and rollover) based on 768 accident samples of an observed weaving section from 2016 to 2018. The modeling results show that drivers’ gender and age, weather condition, traffic density, weaving ratio, vehicle speed, lane change behavior, private cars, season, time period, day of week and accident location are important factors affecting traffic accidents at the weaving section, but they have different contributions to the four traffic accident types. The results also show that traffic density of ≥31 vehicle/100 m has the highest risk of causing rear-end accidents, weaving ration of ≥41% has the highest possibility to bring about a side wipe incident, collision with fixtures is the most likely to happen in snowy weather, and rollover is the most likely incident to occur in rainy weather.

Research on the Method of Dynamic Speed Limit on Expressway under Complex Climate Based on Pavement Skid-Resistant Performance

2013 ◽  
Vol 723 ◽  
pp. 189-195
Author(s):  
Yong Fang ◽  
Zhong Yin Guo
Keyword(s):  
Traffic Safety ◽  
Water Film ◽  
Calculation Model ◽  
Climatic Conditions ◽  
Driving Safety ◽  
Maximum Speed ◽  
Speed Limit ◽  
Vehicle Speed ◽  
Climate Conditions ◽  
Pavement Condition

To solve the problems in the current deterministic method of a maximum speed limit for expressway, a method of dynamic speed limit on expressway under complex climate was presented which was based on pavement skid-resistant performance. Firstly, the variation of pavement skid-resistant performance under complex climate conditions was analysed based on research results and certain experimental statistic data. By analysing the influence rule of AC-16 and SMA-16 pavement texture, pavement temperature, water film thickness, ice thickness, vehicle speed to pavement Skid-Resistant Performance, pavement actual friction coefficient calculation model and reference standard were established under different pavement condition Then, by analysing the geometry line indexes, pavement conditions and vehicle dynamics, the critical sideslip speed and critical longitudinal-driving safety speed was formulated; therefore, with critical speed as a constraint of safety driving and interval classification of complex climatic conditions, the dynamic speed calculate method and safety speed control standard were proposed under various pavements conditions, visibilities and traffic environments. This method for overcoming the weakness of a maximum speed limit of expressway operation and improving traffic safety is helpful.

Road wetness quantification via tyre spray

2018 ◽  
Vol 233 (1) ◽  
pp. 28-37 ◽  
Author(s):  
Bernhard Schmiedel ◽  
Frank Gauterin ◽  
Hans-Joachim Unrau
Keyword(s):  
Vehicle Dynamics ◽  
Autonomous Vehicles ◽  
Water Film ◽  
Significant Loss ◽  
Vehicle Speed ◽  
The Road ◽  
Acceleration Sensors ◽  
On The Road ◽  
Wheel Arch

Road wetness can lead to a significant loss in tyre traction. Although a driver can easily distinguish between dry and wet roads, the thickness of a water film on the road (wetness) and its impact on the vehicle dynamics are more difficult for a driver to classify. Furthermore, autonomous vehicles also need a graded classification of road conditions. There are known sensors, which are able to classify road conditions, but these are either not able to quantify the road wetness or are not suitable for mass production. Therefore, this work analyses a method to measure the road wetness by analysing tyre spray with plain acceleration sensors at positions like wheel arch liner or side skirt. It discusses influences of vehicle speed, road wetness, tyres, road structure and sensor positioning. The results show that a quantification of road wetness is possible, but it relies on the sum of all boundary conditions.

Tire–road friction coefficient estimation based on designed braking pressure pulse

2021 ◽  
pp. 095440702098358
Author(s):  
Juqi Hu ◽  
Subhash Rakheja ◽  
Youmin Zhang
Keyword(s):  
Friction Coefficient ◽  
Unscented Kalman Filter ◽  
Estimation Accuracy ◽  
Accurate Estimation ◽  
Vehicle Speed ◽  
Two Stage ◽  
Slip Ratio ◽  
Road Friction ◽  
Vehicle Motion ◽  
Road Friction Coefficient

Knowledge of tire–road friction coefficient (TRFC) is valuable for autonomous vehicle control and design of active safety systems. This paper investigates TRFC estimation on the basis of longitudinal vehicle dynamics. A two-stage TRFC estimation scheme is proposed that limits the disturbances to the vehicle motion. A sequence of braking pressure pulses is designed in the first stage to identify desired minimal pulse pressure for reliable estimation of TRFC with minimal interference with the vehicle motion. This stage also provides a qualitative estimate of TRFC. In the second stage, tire normal force and slip ratio are directly calculated from the measured signals, a modified force observer based on the wheel rotational dynamics is developed for estimating the tire braking force. A constrained unscented Kalman filter (CUKF) algorithm is subsequently proposed to identify the TRFC for achieving rapid convergence and enhanced estimation accuracy. The effectiveness of the proposed methodology is evaluated through CarSim™-MATLAB/Simulink™ co-simulations considering vehicle motions on high-, medium-, and low-friction roads at different speeds. The results suggest that the proposed two-stage methodology can yield an accurate estimation of the road friction with a relatively lower effect on the vehicle speed.

Automobiles on Horizontal Curves: Experiments and Observations

1998 ◽  
Vol 1628 (1) ◽  
pp. 50-56 ◽  
Author(s):  
Emmanuel Felipe ◽  
Francis Navin
Keyword(s):  
Latin Square ◽  
Lateral Position ◽  
Comfort Level ◽  
Lateral Acceleration ◽  
Small Radius ◽  
Vehicle Speed ◽  
Large Radius ◽  
Horizontal Curves ◽  
Upper Limits ◽  
Curve Radius

Statistical information on the basic variables involved in driving through a horizontal curve was obtained using a 4×4 Latin square design experiment to measure the action of automobile drivers in test track horizontal curves. The independent variables used in the test curves were speed (comfortable, fast); pavement surface (dry, wet); driver (male, female); and curve radius (16 m, 26 m, 60 m, 100 m). The measured output was the driver’s selected speed and corresponding lateral acceleration. In addition, the passengers indicated their comfort level on a four-point semantic scale. Expert drivers also drove the test curves to establish the upper limits of the driver-vehicle-tire system. Field observations of four curves along a two-lane rural mountain highway measured driver vehicle speed, lateral acceleration, and lateral position. The results indicate that, for a comfortable ride, drivers are limited by their comfortable lateral acceleration on small radius curves and seek the “environmental speed” on large radius curves.

Pavement Friction Degradation Based on Pennsylvania Field Test Data

2017 ◽  
Vol 2639 (1) ◽  
pp. 11-19 ◽  
Author(s):  
Lingyu Li ◽  
S. Ilgin Guler ◽  
Eric T. Donnell
Keyword(s):  
Skid Resistance ◽  
Pavement Maintenance ◽  
Horizontal Curves ◽  
Pavement Surface ◽  
Lane Departure ◽  
Roadway Design ◽  
Tire Friction ◽  
Pavement Friction ◽  
Lateral Friction ◽  
Over Time

Pavement surface–tire friction is a critical safety element associated with roadway design, construction, and maintenance practices. The skid resistance of pavements generally declines over time and increases the risk of skidding-related crashes. On horizontal curves, lateral friction may be associated with lane-departure incidents, particularly as the pavement ages and drivers demand more lateral friction than the pavement surface–tire interaction can supply. On tangent roadway sections, longitudinal friction affects braking distances. As the skid-resistance properties of a pavement surface decline over time, braking distances increase, and may increase risks to driver safety. A comprehensive understanding of the process of pavement friction degradation could help highway agencies identify roadway segments that need maintenance to reduce the probability of skid-related incidents. This paper presents a survival analysis of friction degradation for asphalt pavement surfaces. Duration models were estimated with data collected annually along an Interstate highway in Pennsylvania to investigate the degradation of friction over time. These models consider traffic volume and roadway features to determine the probability that friction levels will remain above various friction thresholds. The resulting statistical models can help transportation agencies make better decisions about pavement maintenance to reduce safety risk.

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