Optimization of Lateral Wandering of Automated Vehicles to Reduce Hydroplaning Potential and to Improve Pavement Life

2019 ◽  
Vol 2673 (11) ◽  
pp. 81-89 ◽  
Author(s):  
Fujie Zhou ◽  
Sheng Hu ◽  
Susan T. Chrysler ◽  
Yangwoo Kim ◽  
Ivan Damnjanovic ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Standard Deviation ◽  
Water Film ◽  
Flexible Pavement ◽  
Lateral Position ◽  
Design System ◽  
Automated Vehicles ◽  
Water Films ◽  
Potential Benefits ◽  
Over Time

The deployment of automated vehicles (AVs) has many potential benefits, such as reductions in congestion and emissions, and safety improvements. However, two notable aspects of AVs are their impact on roadway hydroplaning and pavement life. Since most AVs are programmed to follow a set path and maintain a lateral position in the center of the lane, over time, significant rutting will occur in asphalt surfaced pavements. This study measured AV lateral wandering patterns and compared them with human driven vehicles. Both wandering patterns could be modeled with a normal distribution but have significantly different standard deviations. AVs have a standard deviation for the lateral traffic wander pattern at least three times smaller than human driven vehicles. The influences of AVs with smaller lateral wandering on pavement rutting and fatigue life were analyzed with the Texas Mechanistic-Empirical Flexible Pavement Design system. The research discovered that AVs would shorten pavement fatigue life by 20%. Additionally, pavement rut depths (RD) increased by 13% and reached critical values of the RD 30% earlier. Deeper ruts formed more quickly leading to thicker water films on wet roads, and consequently, a much higher risk of hydroplaning. The research also calculated maximum tolerable RDs at different hydroplaning speeds. AVs have a much smaller tolerable RD human driven vehicles because of a greater water film in the rutted wheel path. This research thus proposed an optimal AV lateral wandering pattern: a uniform distribution. A uniformly distributed lateral wandering pattern for AVs prolongs pavement fatigue life, reduces pavement RD, and decreases hydroplaning potential.

First encounter effects in testing of highly automated vehicles during two experimental occasions – The need for recurrent testing

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jonas Andersson ◽  
Azra Habibovic ◽  
Daban Rizgary
Keyword(s):  
Driver Behavior ◽  
Added Value ◽  
Future Research ◽  
Gaze Behavior ◽  
Repeated Testing ◽  
Automated Vehicles ◽  
Automated Driving ◽  
Perceived Safety ◽  
Repeated Interaction ◽  
Over Time

Abstract To explore driver behavior in highly automated vehicles (HAVs), independent researchers are mainly conducting short experiments. This limits the ability to explore drivers’ behavioral changes over time, which is crucial when research has the intention to reveal human behavior beyond the first-time use. The current paper shows the methodological importance of repeated testing in experience and behavior related studies of HAVs. The study combined quantitative and qualitative data to capture effects of repeated interaction between drivers and HAVs. Each driver ( n = 8 n=8 ) participated in the experiment on two different occasions (∼90 minutes) with one-week interval. On both occasions, the drivers traveled approximately 40 km on a rural road at AstaZero proving grounds in Sweden and encountered various traffic situations. The participants could use automated driving (SAE level 4) or choose to drive manually. Examples of data collected include gaze behavior, perceived safety, as well as interviews and questionnaires capturing general impressions, trust and acceptance. The analysis shows that habituation effects were attenuated over time. The drivers went from being exhilarated on the first occasion, to a more neutral behavior on the second occasion. Furthermore, there were smaller variations in drivers’ self-assessed perceived safety on the second occasion, and drivers were faster to engage in non-driving related activities and become relaxed (e. g., they spent more time glancing off road and could focus more on non-driving related activities such as reading). These findings suggest that exposing drivers to HAVs on two (or more) successive occasions may provide more informative and realistic insights into driver behavior and experience as compared to only one occasion. Repeating an experiment on several occasions is of course a balance between the cost and added value, and future research should investigate in more detail which studies need to be repeated on several occasions and to what extent.

scholarly journals Thin-film-induced morphological instabilities over calcite surfaces

2015 ◽  
Vol 471 (2176) ◽  
pp. 20150031 ◽  
Author(s):  
R. Vesipa ◽  
C. Camporeale ◽  
L. Ridolfi
Keyword(s):  
Morphological Evolution ◽  
Water Film ◽  
Environmental Parameters ◽  
Climatic Conditions ◽  
Point Of View ◽  
Theoretical Point ◽  
Carbon Dioxide Transport ◽  
Physical Mechanisms ◽  
Water Films ◽  
Dissolved Ions

Precipitation of calcium carbonate from water films generates fascinating calcite morphologies that have attracted scientific interest over past centuries. Nowadays, speleothems are no longer known only for their beauty but they are also recognized to be precious records of past climatic conditions, and research aims to unveil and understand the mechanisms responsible for their morphological evolution. In this paper, we focus on crenulations, a widely observed ripple-like instability of the the calcite–water interface that develops orthogonally to the film flow. We expand a previous work providing new insights about the chemical and physical mechanisms that drive the formation of crenulations. In particular, we demonstrate the marginal role played by carbon dioxide transport in generating crenulation patterns, which are indeed induced by the hydrodynamic response of the free surface of the water film. Furthermore, we investigate the role of different environmental parameters, such as temperature, concentration of dissolved ions and wall slope. We also assess the convective/absolute nature of the crenulation instability. Finally, the possibility of using crenulation wavelength as a proxy of past flows is briefly discussed from a theoretical point of view.

scholarly journals Effect of hydraulic and mechanical characteristics of sediment layers on water film formation in submarine landslides

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Shogo Kawakita ◽  
Daisuke Asahina ◽  
Takato Takemura ◽  
Hinako Hosono ◽  
Keiji Kitajima
Keyword(s):  
Tensile Strength ◽  
Pore Pressure ◽  
Mechanical Characteristics ◽  
Film Formation ◽  
Mass Movement ◽  
Water Film ◽  
Submarine Landslides ◽  
Overburden Pressure ◽  
Water Films ◽  
Sediment Layers

Abstract Through two lab-scale experiments, we investigated the hydraulic and mechanical characteristics of sediment layers during water film formation, induced by elevated pore pressure—considered one of the triggers of submarine landslides. These involved (1) sandbox experiments to prove the effect of water films on mass movement in low slope gradients and (2) experiments to observe the effect of the tensile strength of semi-consolidated sediment layers on water film formation. Portland cement was used to mimic the degree of sediment cementation. We observed a clear relationship between the amount of cement and pore pressure during water film formation; pressure evolution and sediment deformation demonstrated the hydraulic and mechanical characteristics. Based on the results of these experiments, conditions of the sediment layers during water film formation are discussed in terms of pore pressure, permeability, tensile strength, overburden pressure, and tectonic stresses. The results indicate that the tensile strength of the sediment interface provides critical information on the lower limit of the water film formation depth, which is related to the scale of potential submarine landslides.

Take-Over Time in Highly Automated Vehicles

2018 ◽  
pp. 52-74
Author(s):  
Alexander Eriksson ◽  
Neville A. Stanton
Keyword(s):  
Automated Vehicles ◽  
Over Time

Abstract P084: Neighborhood Characteristics and Changes in Systolic Blood Pressure Over Time: The Multi-Ethnic Study of Atherosclerosis

Circulation ◽  
2015 ◽  
Vol 131 (suppl_1) ◽  
Author(s):  
Paulina Kaiser ◽  
Lynda Lisabeth ◽  
Philippa Clarke ◽  
Sara Adar ◽  
Mahasin Mujahid ◽  
...  
Keyword(s):  
Physical Activity ◽  
Blood Pressure ◽  
Standard Deviation ◽  
Systolic Blood Pressure ◽  
Social Environment ◽  
Social Environments ◽  
Lower Baseline ◽  
Neighborhood Environments ◽  
Physical Activity Environments ◽  
Over Time

Introduction: Research on the association between neighborhood environments and systolic blood pressure (SBP) is limited, predominantly cross-sectional, and has produced mixed results. Investigating specific aspects of neighborhood environments in relation to changes in SBP may help to identify the most important interventions for reducing the population burden of hypertension. Hypothesis: Better neighborhood food, physical activity, and social environments will be associated with lower baseline levels of SBP and smaller increases in SBP over time. Methods: The Multi-Ethnic Study of Atherosclerosis recruited participants from six sites in the U.S., aged 45-84 (mean 59) and free of clinical cardiovascular disease at baseline. Those with non-missing data for key variables were included (N=5,997); the analytic sample was 52.5% female, 39.1% White, 27.3% Hispanic, 11.9% Black, and 21.7% Chinese, with median follow-up time of 9.2 years (IQR 4.5) and SBP measured at three or more exams for 91.3% of participants. SBP in subjects taking anti-hypertensive medication were replaced with multiply imputed estimates of unmedicated SBP, imputed at each exam. Summary measures of neighborhood food and physical activity environments incorporated survey-based scales (healthy food availability and walking environment) and GIS-based measures (density of favorable food stores and recreational resources). The summary measure of the social environment combined survey-based measures of social cohesion and safety. Neighborhoods were defined by a one-mile buffer around each participant’s home address. Linear mixed models were used to model associations of time-varying cumulative average neighborhood environmental summary measures with SBP over time, adjusting for individual-level covariates (demographics, individual- and neighborhood-level SES); models with and without adjustment for baseline SBP were used to evaluate associations of neighborhood environments with SBP trajectories. Results: In models mutually adjusted for all three neighborhood domains and covariates, living in a better physical activity environment was associated with lower SBP at baseline (-1.34 mmHg [95% CI: -2.24, -0.45] per standard deviation higher cumulative average physical activity summary score), while living in a better social environment was associated with higher SBP at baseline (1.00 mmHg [0.39, 1.63] per standard deviation higher); food environment scores were not associated with baseline SBP. After adjustment for baseline SBP, there was no association between any neighborhood environments and trajectories of SBP. Conclusions: Better food and physical activity environments were associated with lower baseline SBP, while better social environments were associated with higher baseline SBP. Neighborhood environments appear to have minimal direct effect on SBP trajectories.

Testing the Theory in Latin America

2020 ◽  
pp. 121-148
Author(s):  
Nicole Baerg
Keyword(s):  
Latin America ◽  
Standard Deviation ◽  
Developed Countries ◽  
Inflation Expectations ◽  
Theoretical Argument ◽  
Instrumental Variable Analysis ◽  
Economic Output ◽  
Information Precision ◽  
The Mean ◽  
Over Time

This chapter moves from studying developed countries to a sample of countries in Latin America over time. The chapter presents evidence that an increase in the information environment, in terms of its level of precision, exerts an attenuating and significant effect on the mean and standard deviation of forecasters’ inflation expectations, ultimately lowering inflation outcomes. The finding is robust to the inclusion of policy credibility, persistence in inflation, economic output, and month and country effects. When conducting instrumental variable analysis, similarly signed results hold. The main results imply that an increase in information precision helps to lower aggregate levels of inflation and that the channel that this works through is by lowering the weight of prior expectations, as predicted by the theoretical argument. Importantly, the results persist even when considering a sample of countries with relatively variable inflation outcomes and less established (and therefore less credible) economic institutions.

Propaganda and Protest in Autocracies

2020 ◽  
pp. 002200272097509
Author(s):  
Erin Baggott Carter ◽  
Brett L. Carter
Keyword(s):  
Standard Deviation ◽  
Half Life ◽  
Popular Protest ◽  
Original Dataset ◽  
Initial Effect ◽  
Temporal Persistence ◽  
Over Time

Does propaganda reduce the rate of popular protest in autocracies? To answer this question, we draw on an original dataset of state-run newspapers from thirty countries, encompassing six languages and over four million articles. We find that propaganda diminishes the rate of protest, and that its effects persist over time. By increasing the level of pro-regime propaganda by one standard deviation, autocrats have reduced the odds of protest the following day by 15%. The half-life of this effect is between five and ten days, and very little of the initial effect persists after one month. This temporal persistence is remarkably consistent with campaign advertisements in democracies.

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