scholarly journals Investigating Automobile Passengers’ Comfort and Safety on Scenic Road Using Sideway Force Coefficient

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Ronghua Wang ◽  
Xingliang Liu ◽  
Feijie Han
Keyword(s):  
Numerical Simulation ◽  
Large Scale ◽  
Lateral Acceleration ◽  
Driving Safety ◽  
Horizontal Curve ◽  
Force Coefficient ◽  
Safe Driving ◽  
Minimum Radius ◽  
Curve Design ◽  
Naturalistic Driving

To satisfy passengers’ experiential demand in scenic roads, a study on passengers’ comfort in the aspect of horizontal curve design is stated in this study. A new indicator sideway force coefficient (SFC) describing passengers’ comfort is introduced, which differs from lateral acceleration. The mechanism of SFC is provided depending on the dynamic balance condition of the vehicle on horizontal curve and S F C c representing passengers’ comfort tolerance limitation is investigated. A large scale naturalistic driving experiments along a park road are conducted, and the S F C c value from naturalistic driving experiments is verified through numerical simulation of 15 horizontal curves from 5 scenic roads from the perspectives of both passengers’ comfort and driving safety. The statistical analysis on data collected in field tests indicates that age and gender have no effect on S F C c , and the value of S F C c is determined as 0.291. The corresponding minimum radius limits under 20–60 km/h and superelevation 6%, 8%, and 10% are proposed. The numerical simulation denotes, when satisfying the comfort demand of passengers (SFC less than 0.291), the lateral distance path is in a safe range, which could also satisfy the safe driving requirements. Thus, S F C c and minimum radius limits proposed in this study are proved to be credible and appropriate for the curve design of horizontal alignment in scenic roads.

scholarly journals An investigation on the link between driver demographic characteristics and distracted driving by using the SHRP 2 naturalistic driving data

2020 ◽  
Vol 3 (1) ◽  
pp. 1-16
Author(s):  
Haotian Cao ◽  
Zhenghao Zhang ◽  
Xiaolin Song ◽  
Hong Wang ◽  
Mingjun Li ◽  
...  
Keyword(s):  
Cell Phone ◽  
Large Scale ◽  
Population Attributable Risk ◽  
Demographic Characteristics ◽  
Driving Safety ◽  
Crash Risk ◽  
Lower Percentage ◽  
Content Type ◽  
Driving Experience ◽  
Naturalistic Driving

Purpose The purpose of this paper is to investigate the influence of driver demographic characteristics on the driving safety involving cell phone usages. Design/methodology/approach A total of 1,432 crashes and 19,714 baselines were collected for the Strategic Highway Research Program 2 naturalistic driving research. The authors used a case-control approach to estimate the prevalence and the population attributable risk percentage. The mixed logistic regression model is used to evaluate the correlation between different driver demographic characteristics (age, driving experience or their combination) and the crash risk regarding cell phone engagements, as well as the correlation among the likelihood of the cell phone engagement during the driving, multiple driver demographic characteristics (gender, age and driving experience) and environment conditions. Findings Senior drivers face an extremely high crash risk when distracted by cell phone during driving, but they are not involved in crashes at a large scale. On the contrary, cell phone usages account for a far larger percentage of total crashes for young drivers. Similarly, experienced drivers and experienced-middle-aged drivers seem less likely to be impacted by the cell phone while driving, and cell phone engagements are attributed to a lower percentage of total crashes for them. Furthermore, experienced, senior or male drivers are less likely to engage in cell phone-related secondary tasks while driving. Originality/value The results provide support to guide countermeasures and vehicle design.

Framework for Reliability-Based, Safety-Explicit Horizontal Curve Design using Naturalistic Driving Data

2019 ◽  
Vol 2673 (4) ◽  
pp. 605-615
Author(s):  
Bashar Dhahir ◽  
Yasser Hassan
Keyword(s):  
Driver Behavior ◽  
Safety Evaluation ◽  
Safety Performance ◽  
Point Mass ◽  
Horizontal Curve ◽  
Mass Model ◽  
Reliability Indices ◽  
Curve Design ◽  
Naturalistic Driving ◽  
Favorable Weather

The design of horizontal curves is generally based on a deterministic analysis of driver comfort using a point-mass model based on data mostly from the early 1900s and might be outdated. Furthermore, the design lacks quantitative safety evaluation. This paper proposes a new framework for horizontal curve design that provides a quantitative evaluation of safety performance. The framework uses recently collected data from the naturalistic driving study (NDS) to develop models to predict distributions of parameters that reflect contemporary driver behavior, such as speed on curve and comfort threshold in favorable weather and rainy conditions. Statistical models were also developed for more accurate evaluation of vehicle dynamic parameters than the point-mass model. The variability of driver behavior and vehicle dynamics parameters was considered using reliability analysis to develop surrogate safety measures for four design criteria: vehicle stability, comfort threshold, sight distance, and rollover. Safety performance functions were then developed to relate reliability indices to expected safety performance. The results showed that only the driver comfort criterion was not significantly related to expected safety performance. A design example was presented using the proposed framework, which showed the expected change of safety performance of the curve being considered. An optimum radius was then found to minimize the number of expected collisions.

scholarly journals Research on the road linear optimization design of bridge and tunnel connecting segment in the canyon

2019 ◽  
Vol 52 (4) ◽  
pp. 67-79
Author(s):  
Lu Wang ◽  
Yuwen Liu ◽  
Xiaoxin Chen
Keyword(s):  
Traffic Management ◽  
Optimization Design ◽  
Linear Optimization ◽  
Lateral Acceleration ◽  
Speed Limit ◽  
Force Coefficient ◽  
Minimum Radius ◽  
The Road ◽  
On The Road ◽  
Circular Curve

It is easy to skid and roll by centrifugal force and wind, which affects the safety of the vehicle. At the same time, the special location of bridge and tunnel connecting segment in the canyon will accelerate the wind, and make the transverse wind play a more important role in driving vehicles. Based on the acceleration effect of canyons on wind, the vehicle model is simulated by Carsim software, and the road and wind models are established. It is studied that the vehicle has different radius of circular curve under different wind levels, corresponding to different superelevation. The lateral acceleration, lateral deflection and transverse force coefficient are selected as the running state of the vehicle at different speeds to research the linear optimization design of bridge and tunnel connecting segment in the canyon. The result shows that when the wind force exceeds the fifth grade, it is possible for the vehicle to overturn under the limit minimum radius required by the standard value. In order to ensure the stability and safety of the vehicle, this paper considers the geographical position of bridge and tunnel connecting segment in the canyon and the relationship between the radius of the superelevation and circular curve. What’s more, it puts forward the optimal limit minimum radius of the circular curve with different wind grades of 5-9 grades. At the same time, when the road alignment cannot be optimized under the condition, this paper puts forward the speed limit that the vehicle safety can be guaranteed under different wind speed conditions. The speed limit can provide reference for traffic management and safety guarantee of mountain expressway.

Development and Adoption of Early AASHO Design Criteria

1998 ◽  
Vol 1612 (1) ◽  
pp. 26-33 ◽  
Author(s):  
Jerome Hall ◽  
Daniel Turner
Keyword(s):  
Design Parameters ◽  
Design Criteria ◽  
Adoption Process ◽  
Horizontal Curve ◽  
Highway Design ◽  
Initial Development ◽  
Design Processes ◽  
Blue Book ◽  
Curve Design ◽  
Independent Design

The conception, development, and adoption of early AASHO highway design criteria are documented. Examining the early efforts states used to select a design vehicle and develop horizontal curve design criteria illustrates why AASHO’s leadership was necessary. AASHO’s slow and somewhat haphazard criteria development, and the disparity from state to state, demonstrated the need for a national consensus in highway design parameters. AASHO’s role in providing these criteria is outlined through its initial development of policy booklets, followed by its 1954 publication of the landmark Blue Book. The processes by which nine states adopted the AASHO guidance are briefly reviewed. In several cases, the AASHO policy was embraced immediately, and in others it was accepted slowly as states clung to their independent design processes and only gradually updated their design criteria. A few simple conclusions are drawn about the development and adoption process, particularly as it may relate to tomorrow’s highway design criteria.

scholarly journals Numerical Simulation of EPB Shield Tunnelling with TBM Operational Condition Control Using Coupled DEM–FDM

2021 ◽  
Vol 11 (6) ◽  
pp. 2551
Author(s):  
Hyobum Lee ◽  
Hangseok Choi ◽  
Soon-Wook Choi ◽  
Soo-Ho Chang ◽  
Tae-Ho Kang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Large Scale ◽  
Tunnel Boring Machine ◽  
Chamber Pressure ◽  
Screw Conveyor ◽  
Shield Tunnel ◽  
Pressure Balance ◽  
Operational Conditions ◽  
Shield Tunnelling ◽  
Epb Shield

This study demonstrates a three-dimensional numerical simulation of earth pressure balance (EPB) shield tunnelling using a coupled discrete element method (DEM) and a finite difference method (FDM). The analysis adopted the actual size of a spoke-type EPB shield tunnel boring machine (TBM) consisting of a cutter head with cutting tools, working chamber, screw conveyor, and shield. For the coupled model to reproduce the in situ ground condition, the ground formation was generated partially using the DEM (for the limited domain influenced by excavation), with the rest of the domain being composed of FDM grids. In the DEM domain, contact parameters of particles were calibrated via a series of large-scale triaxial test analyses. The model simulated tunnelling as the TBM operational conditions were controlled. The penetration rate and the rotational speed of the screw conveyor were automatically adjusted as the TBM advanced to prevent the generation of excessive or insufficient torque, thrust force, or chamber pressure. Accordingly, these parameters were maintained consistently around their set operational ranges during excavation. The simulation results show that the proposed numerical model based on DEM–FDM coupling could reasonably simulate EPB driving while considering the TBM operational conditions.

scholarly journals Optimal Design of Slit Impeller for Low Specific Speed Centrifugal Pump Based on Orthogonal Test

2021 ◽  
Vol 9 (2) ◽  
pp. 121
Author(s):  
Yang Yang ◽  
Ling Zhou ◽  
Hongtao Zhou ◽  
Wanning Lv ◽  
Jian Wang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Centrifugal Pump ◽  
Large Scale ◽  
Internal Flow ◽  
Orthogonal Test ◽  
Centrifugal Pumps ◽  
Initial Model ◽  
Low Specific Speed ◽  
Specific Speed ◽  
Four Levels

Marine centrifugal pumps are mostly used on board ship, for transferring liquid from one point to another. Based on the combination of orthogonal testing and numerical simulation, this paper optimizes the structure of a drainage trough for a typical low-specific speed centrifugal pump, determines the priority of the various geometric factors of the drainage trough on the pump performance, and obtains the optimal impeller drainage trough scheme. The influence of drainage tank structure on the internal flow of a low-specific speed centrifugal pump is also analyzed. First, based on the experimental validation of the initial model, it is determined that the numerical simulation method used in this paper is highly accurate in predicting the performance of low-specific speed centrifugal pumps. Secondly, based on the three factors and four levels of the impeller drainage trough in the orthogonal test, the orthogonal test plan is determined and the orthogonal test results are analyzed. This work found that slit diameter and slit width have a large impact on the performance of low-specific speed centrifugal pumps, while long and short vane lap lengths have less impact. Finally, we compared the internal flow distribution between the initial model and the optimized model, and found that the slit structure could effectively reduce the pressure difference between the suction side and the pressure side of the blade. By weakening the large-scale vortex in the flow path and reducing the hydraulic losses, the drainage trough impellers obtained based on orthogonal tests can significantly improve the hydraulic efficiency of low-specific speed centrifugal pumps.

Modeling Safety Effects of Horizontal Curve Design on Injury Severity of Single-Motorcycle Crashes with Mixed-Effects Logistic Model

2017 ◽  
Vol 2637 (1) ◽  
pp. 38-46 ◽  
Author(s):  
Chunfu Xin ◽  
Zhenyu Wang ◽  
Chanyoung Lee ◽  
Pei-Sung Lin
Keyword(s):  
Logistic Model ◽  
Injury Severity ◽  
Unobserved Heterogeneity ◽  
Mixed Effects ◽  
Severe Injury ◽  
Horizontal Curve ◽  
Random Parameters ◽  
Horizontal Curves ◽  
Curve Design ◽  
Motorcycle Crashes

Horizontal curves have been of great interest to transportation researchers because of expected safety hazards for motorcyclists. The impacts of horizontal curve design on motorcycle crash injuries are not well documented in previous studies. The current study aimed to investigate and to quantify the effects of horizontal curve design and associated factors on the injury severity of single-motorcycle crashes with consideration of the issue of unobserved heterogeneity. A mixed-effects logistic model was developed on the basis of 2,168 single-motorcycle crashes, which were collected on 8,597 horizontal curves in Florida for a period of 11 years (2005 to 2015). Four normally distributed random parameters (moderate curves, reverse curves, older riders, and male riders) were identified. The modeling results showed that sharp curves (radius <1,500 ft) compared with flat curves (radius ≥4,000 ft) tended to increase significantly the probability of severe injury (fatal or incapacitating injury) by 7.7%. In total, 63.8% of single-motorcycle crashes occurring on reverse curves are more likely to result in severe injury, and the remaining 26.2% are less likely to result in severe injury. Motorcyclist safety compensation behaviors (psychologically feeling safe, and then riding aggressively, or vice versa) may result in counterintuitive effects (e.g., vegetation and paved medians, full-access-controlled roads, and pavement conditions) or random parameters (e.g., moderate curve and reverse curve). Other significant factors include lighting conditions (darkness and darkness with lights), weekends, speed or speeding, collision type, alcohol or drug impairment, rider age, and helmet use.

Prognostic criteria for Polar Lows

2021 ◽  
Author(s):  
Natalia Vazaeva ◽  
Otto Chkhetiani ◽  
Michael Kurgansky
Keyword(s):  
Numerical Simulation ◽  
Wind Velocity ◽  
Large Scale ◽  
Satellite Image ◽  
Development Stage ◽  
Mature Stage ◽  
Initial Development ◽  
Polar Lows ◽  
Prognostic Criteria ◽  
Main Challenge

&lt;p&gt;Polar lows (PLs) are important mesoscale (horizontal diameter up to 1000 km) maritime weather systems at high latitudes, forming pole ward from the polar front. We consider the possible prognostic criteria of PLs, in particular, the kinematic helicity as a quadratic characteristic related to the integral vortex formations and the kinematic vorticity number (KVN). To calculate such characteristics we use reanalysis data and the results of numerical simulation with the WRF-ARW model (Version 4.1.) for the PLs over the Nordic (Norwegian and Barents) seas. For comparison, experimental data are used.&lt;/p&gt;&lt;p&gt;Our estimate of helicity is based on the connection of an integral helicity (IH) in the Ekman layer with the geostrophic wind velocity, due to the good correlation between IH and half the sum of the wind velocity squared. We have chosen IH averaged over preselected area covering the locality of PLs genesis. This area was moving along with the centre of PL during the numerical simulation.&lt;/p&gt;&lt;p&gt;The genesis of PLs can be divided into three stages: (i) an initial development stage, in which a number of small vortices appear in a shear zone; (ii) a late development stage, characterized by the merger of vortices; (iii) a mature stage, in which only a single PL is present. Approximately one day before PL formation, a significant increase in helicity was observed. The average helicity bulk density of large-scale motions has values of 0.3 &amp;#8211; 0.4 ms&lt;sup&gt;-2&lt;/sup&gt;. The local changes in helicity are adjacent to the front side of the PLs. The IH criterion described facilitates the identification of the PLs genesis area. For a more detailed analysis of the PL genesis, it is recommended to apply KVN, which is the additional indicator of PL size and intensity. At the moment of maximum intensity of PLs KVN can reach values of 12 &amp;#8211; 14 units. The advantage of using KVN is also in its clear change directly in the centre of the emerging PLs, which allows to precisely indicates the limits of the most intense part of PLs.&lt;/p&gt;&lt;p&gt;The main challenge is to make the operational forecast of PLs possible through the selection of the prognostic integral characteristics of PLs, sufficient for PLs identification and for analysis of their size and intensity in a convenient, usable and understandable way. The criteria associated with vorticity and helicity are reflected in the PLs genesis and development quite clearly. At this time, such a claim is only a hypothesis, which must be tested using a larger set of cases. Future work will need to extend these analyses to other active PL basins. Also, it would be interesting to compare the representation of PLs by using any other criteria. It is intended to use our combined criteria as a precursor to machine learning-based PLs identification procedure where satellite image analysis and capture of particular cloud patterns are currently applied in most of the cases. It would eliminate the time consuming first stage of collecting data sets.&lt;/p&gt;&lt;p&gt;This work was supported by the Russian Science Foundation (project No. 19-17-00248).&lt;/p&gt;

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