California Drivers Research Articles

Organizing at the Digital Water Cooler: Social Media, Platform Organizing, and the Fight against Surveillance Capitalism

This article explores how Rideshare Drivers United (RDU), a fledgling union of app-based drivers in California, works in dialectical relationship to processes of surveillance capitalism. First, the article gives a brief history of RDU's organizing strategy in the lead-up to two strikes in the spring of 2019. RDU capitalized on social media's advertising platforms, as well as on a purpose-built app called Solidarity, to bring together a disparate workforce. Next, drawing on Vincent Mosco's framework for the political economy of communication, the article describes how this strategy emerged in response to, and intervened in, the processes of commodification, spatialization, and structuration that constitute surveillance capitalism. Interviews with Los Angeles– and San Diego–area driver-organizers suggest that this use of digital tools has become a mundane feature of the contemporary labor and social life. The refusal to fetishize platforms opens space for app-based workers to challenge surveillance capitalism's logics through platform organizing.

High-resolution mapping of wildfire drivers in California based on machine learning

Wildfires are important natural disturbances of ecosystems; however, they threaten the sustainability of ecosystems, climate and humans worldwide. It is vital to quantify and map the controlling drivers of wildfires for effective wildfire prediction and risk management. However, high-resolution mapping of wildfire drivers remains challenging. Here we established machine-learning (Random Forests) models using 23 climate and land surface variables as model inputs to reconstruct the spatial variability and seasonality of wildfire occurrence and extent in California. The importance of individual drivers was then quantified based on the Shapley value method. Thus, we provided spatially resolved maps of wildfire drivers at high resolutions up to 0.004° × 0.004°. The results indicated that precipitation and soil moisture are the major drivers dominating 37% of the total burnt area for large and extreme wildfires in summer and 63% in autumn, while elevation plays a major role for 15–58% of burnt areas in small wildfires in all seasons. Winds are also an important contributor to summer wildfires, accounting for 41% of large and extreme burnt areas. This study enhanced our knowledge of spatial variability of wildfire drivers across diverse landscapes in a fine-scale mapping, providing valuable perspectives and case studies for other regions of the world with frequently occurred wildfire.

A hydrologic feature detection algorithm to quantify seasonal components of flow regimes

Seasonal flow transitions between wet and dry conditions are a primary control on river conditions, including biogeochemical processes and aquatic life-history strategies. In regions like California with highly seasonal flow patterns and immense interannual variability, a rigorous approach is needed to accurately identify and quantify seasonal flow transitions from the annual flow regime. Drawing on signal processing theory, this study develops a transferable approach to detect the timing of seasonal flow transitions from daily streamflow time series using an iterative smoothing, feature detection, and windowing methodology. The approach is shown to accurately identify and characterize seasonal flows across highly variable natural flow regimes in California. A quantitative error assessment validated the accuracy of the approach, finding that inaccuracies in seasonal timing identification did not exceed 10%, with infrequent exceptions. Results for seasonal timing were also used to highlight the statistically distinct timing found across streams with varying climatic drivers in California. The proposed approach improves understanding of spatial and temporal trends in hydrologic processes and climate conditions across complex landscapes and informs environmental water management efforts by delineating timing of seasonal flows.

Are millennials more multimodal? A latent-class cluster analysis with attitudes and preferences among millennial and Generation X commuters in California

Millennials tend to use a variety of travel modes more often than older birth cohorts. Two potential explanations for this phenomenon prevail in the literature. According to the first explanation, millennials often choose travel multimodality at least in part because of the effects of the economic crisis, which affected young adults more severely than their older counterparts. Another explanation points to the fact that millennials may have fundamentally different preferences from those of older birth cohorts. This paper presents an examination of millennials’ travel behavior as compared to the preceding Generation X, based on a survey of 1069 California commuters. It shows that millennials adopt multimodality more often than Gen Xers, on average. However, the analysis also points to substantial heterogeneity among millennials and indicates that, perhaps contrary to expectations and the stereotype in the media, the majority of millennials are monomodal drivers in California. The paper contributes to the literature on millennials’ mobility in several ways. First, it rigorously classifies various forms of travel multimodality (on a monthly basis and distinctively taking trip purpose into account) through the analysis of a rich dataset that includes individual attitudes and preferences; second, it explores gradual changes of multimodality across age and generation; and third, it analyzes the effects of various demographic, built environment, and attitudinal attributes on the adoption of multimodality.

Drinking and driving and perceptions of arrest risk among California drivers: Relationships with DUI arrests in their city of residence

ABSTRACTObjective: Addressing drinking and driving remains a challenge in the United States. The present study aims to provide feedback on driving under the influence (DUI) in California by assessing whether drinking and driving behavior is associated with the DUI arrest rates in the city in which the driver lives; whether this is due to perceptions that one can get arrested for this behavior; and whether this differed by those drivers who would be most affected by deterrence efforts (those most likely to drink outside the home).Methods: This study consisted of a 2012 roadside survey of 1,147 weekend nighttime drivers in California. City DUI arrest rates for 2009–2011 were used as an indicator of local enforcement efforts. Population average logistic modeling was conducted modeling the odds of perceived high arrest likelihood for DUI and drinking and driving behavior within the past year.Results: As the DUI arrest rates for the city in which the driver lives increased, perceived high risk of DUI arrest increased. There was no significant relationship between either city DUI arrest rates or perceived high risk of DUI arrest with self-reported drinking and driving behavior in the full sample. Among a much smaller sample of those most likely to drink outside the home, self-reported drinking and driving behavior was negatively associated with DUI arrests rates in their city of residence but this was not mediated by perceptions.Conclusion: The results of the present study suggest that perceptions are correlated with one aspect of DUI efforts in one's community. Those who were more likely to drink outside the home could be behaviorally influenced by these efforts.

Customizing driving cycles to support vehicle purchase and use decisions: Fuel economy estimation for alternative fuel vehicle users

Wider deployment of alternative fuel vehicles (AFVs) can help with increasing energy security and transitioning to clean vehicles. Ideally, adopters of AFVs are able to maintain the same level of mobility as users of conventional vehicles while reducing energy use and emissions. Greater knowledge of AFV benefits can support consumers’ vehicle purchase and use choices. The Environmental Protection Agency’s fuel economy ratings are a key source of potential benefits of using AFVs. However, the ratings are based on pre-designed and fixed driving cycles applied in laboratory conditions, neglecting the attributes of drivers and vehicle types. While the EPA ratings using pre-designed and fixed driving cycles may be unbiased they are not necessarily precise, owning to large variations in real-life driving. Thus, to better predict fuel economy for individual consumers targeting specific types of vehicles, it is important to find driving cycles that can better represent consumers’ real-world driving practices instead of using pre-designed standard driving cycles. This paper presents a methodology for customizing driving cycles to provide convincing fuel economy predictions that are based on drivers’ characteristics and contemporary real-world driving, along with validation efforts. The methodology takes into account current micro-driving practices in terms of maintaining speed, acceleration, braking, idling, etc., on trips. Specifically, using a large-scale driving data collected by in-vehicle Global Positioning System as part of a travel survey, a micro-trips (building block) library for California drivers is created using 54million seconds of vehicle trajectories on more than 60,000 trips, made by 3000 drivers. To generate customized driving cycles, a new tool, known as Case Based System for Driving Cycle Design, is developed. These customized cycles can predict fuel economy more precisely for conventional vehicles vis-à-vis AFVs. This is based on a consumer’s similarity in terms of their own and geographical characteristics, with a sample of micro-trips from the case library. The AFV driving cycles, created from real-world driving data, show significant differences from conventional driving cycles currently in use. This further highlights the need to enhance current fuel economy estimations by using customized driving cycles, helping consumers make more informed vehicle purchase and use decisions.

What If? Re-imagined Scenarios and the Re-Virtualisation of History

What If? Re-imagined Scenarios and the Re-Virtualisation of History

Acceptance of drinking and driving and alcohol-involved driving crashes in California

BackgroundAlcohol-impaired driving accounts for substantial proportion of traffic-related fatalities in the U.S. Risk perceptions for drinking and driving have been associated with various measures of drinking and driving behavior. In an effort to understand how to intervene and to better understand how risk perceptions may be shaped, this study explored whether an objective environmental-level measure (proportion of alcohol-involved driving crashes in one’s residential city) were related to individual-level perceptions and behavior. MethodsUsing data from a 2012 cross-sectional roadside survey of 1147 weekend nighttime drivers in California, individual-level self-reported acceptance of drinking and driving and past-year drinking and driving were merged with traffic crash data using respondent ZIP codes. Population average logistic regression modeling was conducted for the odds of acceptance of drinking and driving and self-reported, past-year drinking and driving. ResultsA non-linear relationship between city-level alcohol-involved traffic crashes and individual-level acceptance of drinking and driving was found. Acceptance of drinking and driving did not mediate the relationship between the proportion of alcohol-involved traffic crashes and self-reported drinking and driving behavior. However, it was directly related to behavior among those most likely to drink outside the home. DiscussionThe present study surveys a particularly relevant population and is one of few drinking and driving studies to evaluate the relationship between an objective environmental-level crash risk measure and individual-level risk perceptions. In communities with both low and high proportions of alcohol-involved traffic crashes there was low acceptance of drinking and driving. This may mean that in communities with low proportions of crashes, citizens have less permissive norms around drinking and driving, whereas in communities with a high proportion of crashes, the incidence of these crashes may serve as an environmental cue which informs drinking and driving perceptions. Perceptual information on traffic safety can be used to identify places where people may be at greater risk for drinking and driving. Community-level traffic fatalities may be a salient cue for tailoring risk communication.

The impact of marijuana decriminalization on California drivers

BackgroundThe liberalization of marijuana laws has led to concerns that such changes will increase “drugged driving” and crash-related mortality. California decriminalized marijuana effective January 1, 2011; we examine the impact of this change on marijuana-involved driving. MethodsWe used laboratory testing from roadside surveys and the Fatality Analysis Reporting System (FARS) to assess impacts on weekend nighttime drivers and fatally injured drivers, respectively. We calculated marijuana prevalence (measured by laboratory-confirmed delta-9-tetrahydrocannabinol [THC] in roadside surveys and cannabinoids in FARS) and compared corresponding 95% confidence intervals (CI) to identify statistically significant changes post-decriminalization. We also conducted multiple logistic regression analyses to determine whether the odds of marijuana-involved driving increased significantly after controlling for potential confounders. ResultsThere was no statistically significant change in the prevalence of THC-positive driving among weekend nighttime drivers (n=894) in 2012 (9.2%; 95% CI: 6.3, 12.2) compared to 2010 (11.3%; 95% CI: 8.5, 14.0) or in the adjusted odds of testing positive for THC (adjusted odds ratio [AOR]=0.96; 95% CI: 0.57, 1.60). In contrast, we found a statistically significant increase in the prevalence of cannabinoids among fatally injured drivers in 2012 (17.8%; 95% CI: 14.6, 20.9) compared to the pre-decriminalization period 2008–2010 (11.8%; 95% CI: 10.3, 13.3). The adjusted odds of testing positive for cannabinoids were also significantly higher in 2012 (AOR=1.67; 95% CI: 1.28, 2.18). ConclusionsOur study generated discrepant findings regarding the impact of decriminalization on marijuana-involved driving in California. Factors that may have contributed to these findings, particularly methodological factors, are discussed.

Non-compliance with graduated driver licensing (GDL) requirements: Changes in GDL-related conviction rates over time among 16–17-year-old California drivers

IntroductionSelf-reports by novice teen drivers in California and elsewhere suggest that many violate graduated driver licensing (GDL) nighttime and passenger restrictions, and to a lesser extent, drive on learner permits without being supervised. Is this corroborated by their traffic conviction records? MethodWe examined historical aggregated conviction rates for GDL-related violations before and after GDL, and Poisson regressions of conviction rates over time among 16–17-year-old California novices. ResultsDuring the year before they received their provisional licenses, <1% of 16-year-old novices and <2% of 17-year-old novices were convicted of driving unlicensed or unsupervised on their learner permits. Statewide historical conviction rates for these offenses were not higher after GDL was implemented, despite the longer holding period. Convictions for violating GDL nighttime or passenger restrictions were highest almost immediately after provisional licensure, though only about 3% of 16-year-old novices and 2% of 17-year-old novices were ever convicted of violating either restriction. DiscussionCalifornia 16–17-year-old novice drivers were very rarely convicted of GDL-related violations. The contradictive, large differences between the current findings and self-report surveys are likely due in part to the fact that most self-reports assessed only whether teens had ever violated a GDL-related requirement, which exaggerates prevalence. Our conviction findings are more similar to estimates of non-compliance with GDL-related requirements from naturalistic driving studies that monitor actual driving behavior and take exposure into account, but are lower likely due to issues related to detection, enforcement, and adjudication of violations, as well as limitations of existing naturalistic studies.

Crash and traffic violation rates before and after licensure for novice California drivers subject to different driver licensing requirements

IntroductionHow do crash and traffic violation rates for novice 16–17-year-old drivers change over the months before and after licensure under a graduated driver licensing (GDL) program relative to those for older novices who are not subject to GDL? MethodPlots and Poisson regression comparing overall rates and subtypes of crashes and traffic violations among California novice drivers ages 16 to 35years over time before and after unsupervised licensure. ResultsMajorities of 16-year-olds (57%) and 17-year-olds (73%) actually hold their learner permits longer than the required 6months; majorities (67%–81%) of age 18 or older novices hold their learner permits less than 6months. Crash rates of novice 16- and 17-year-olds—as well as most other age groups—are highest almost immediately after they are licensed to drive unsupervised, after which their rates decline quickly during their first year of licensure and at a slower rate for the second and third years. Novice 16- and 17-year-olds' traffic violation rates reach their zenith long after their total crash rates peak and decline, whereas violation rates for older novices peak during their first year of licensure. Over 70% of 16- and 17-year-old novices are crash-free for the first 3years of licensure. ConclusionsWhile novice 16- and 17-year-olds' highest crash rates occur almost immediately after they are licensed, their peak traffic violation rates are delayed until around the time they turn age 18. Both pre-licensure crash rates and post-licensure crash peaks were more pronounced for some older age groups of novices than was the case for 16–17-year-olds. Practical ApplicationsExtending learner permit holding periods for 16–17-year-old novices appears consistent with their actual behavior; requiring older novices—particularly those ages 18 to 20—to hold permits for minimum periods may reduce their initial crash rates.

Estimating the over-involvement of suspended, revoked, and unlicensed drivers as at-fault drivers in California fatal crashes

Introduction and MethodQuasi-induced exposure analysis was used to estimate annual fatal crash involvement rates for validly licensed, suspended or revoked (S/R), and unlicensed drivers in California from 1987 through 2009 using fatal crash data obtained from the National Highway Traffic Safety Administration's Fatality Analysis Reporting System and crash culpability determinations from the California Highway Patrol's Statewide Integrated Traffic Records System. ResultsAlthough there was some year-to-year fluctuation in the annual estimates, S/R and unlicensed drivers were over-involved as at-fault drivers in fatal crashes during every year of the 23-year time period relative to validly licensed drivers. The fatal crash involvement ratios combined across all years were 0.86 for validly licensed drivers, 2.23 for S/R drivers, and 2.34 for unlicensed drivers. Hence, compared to validly licensed drivers, the odds of being at-fault for a fatal crash were 160% higher for S/R drivers (involvement ratio=2.60) and 173% higher for unlicensed drivers (involvement ratio=2.73). The excess risks of S/R and unlicensed drivers are somewhat lower than estimates found in a prior study using the same technique, but the results nonetheless provide evidence that S/R and unlicensed drivers are much more hazardous on the road than are validly licensed drivers and emphasize the importance of using strong countermeasures—including vehicle impoundment—to reduce their high crash risk. These findings support interventions to help reduce driving among S/R and unlicensed drivers.

Observational Study of use of Cell Phone and Texting among Drivers in California

This methodological report describes survey research and data collection methods used for the second Observational Survey of Cell Phone and Texting Use Among California Drivers study conducted in 2012. This study was conducted by Ewald &amp; Wasserman Research Consultants on behalf of the California Office of Traffic Safety and the Safe Transportation Research and Education Center at the University of California, Berkeley. The goal of the survey was to obtain a statewide statistically representative observational sample of California's cell phone use behaviors, focusing on mobile device use and comparing it with the 2011 survey data. Vehicle drivers were observed at controlled intersections, such as traffic lights and stop signs; a protocol similar to the National Occupancy Protection Use Study methodology published by NHTSA was used. The sample frame included a total of 5,664 vehicle observations from 129 sites. The total percentage of drivers distracted by electronic devices (holding a phone to the ear, manipulating a handheld electronic device while driving, or talking on a handheld device) increased to 6.2% in 2012 from 4.2% in 2011. California's baseline level of cell phone use and driving will be a critical metric over the years as traffic safety stakeholders mobilize to conduct high-visibility enforcement campaigns, explore new policies, expand educational programs, and engineer countermeasures to increase safety on the roads.

RFID, GPS, and 3G: Radio Wave Technologies and Privacy

I recently read an article in Wired magazine1 about the decision to suspend the plan to embed RFID (radio frequency identification) chips in California driver’s licenses. A driver’s license with an RFID tag in it is call ed an Enhanced Driver’s License (EDL).2 The argument in favor of the EDL plan was, of course, convenience. The argument against the plan was, of course, privacy. And like many conversations about convenience versus privacy, a big dose of facts would be helpful.

Observational Survey of Cell Phone Use and Texting by California Drivers, 2011

This methodological report describes survey research and data collection methods employed for the first observational survey of cell phone use and texting by California drivers. This study was conducted by Ewald and Wasserman Research Consultants on behalf of the California Office of Traffic Safety and the Safe Transportation Research and Education Center at the University of California, Berkeley. The goal of the survey was to obtain a statewide, statistically representative observational sample. Vehicle drivers were observed at controlled intersections, such as traffic lights and stop signs, using a protocol similar to the National Occupancy Protection Use Study methodology published by the National Highway Traffic Safety Administration. Seventeen California counties were included in the sample frame, and 5,413 valid observations were made. Overall, 4.2% of drivers observed were using a cell phone while driving (phone to ear, manipulating a handheld device, talking on a handheld device, or talking via a headset or Bluetooth device). Because of the difficulty of observing hands-free use, previously used methods were applied to estimate this use at 4.8%. Therefore, an estimate of overall cell phone use in California during the survey period is 9%. California's baseline level of cell phone use and driving will be a critical metric over the years as traffic safety stakeholders mobilize to conduct high-visibility enforcement campaigns, explore new policies, expand educational programs, and engineer countermeasures to increase safety on the roads.

Driving Under the (Cellular) Influence

Previous research in the laboratory and by epidemiologists has compared the danger of cell phone use while driving to that of illicit levels of alcohol. This paper investigates the causal link between driver cell phone use and crash rates by exploiting a natural experiment -- the discontinuity in marginal pricing at 9pm on weekdays from 2002 to 2005 when cellular plans transitioned from peak to off-peak pricing. We first documented that the pricing threshold induced a 7.2% jump on Mondays to Thursdays in call likelihood for a large and proprietary sample of drivers in California from 2005. Two additional datasets of calls, drawn from drivers and non-drivers nationwide, affirm the price sensitivity of cell phone users. We next document the corresponding change in the crash rate for California as well as the eight additional states for which we have the universe of crash data. Using a period prior to the prevalence of 9pm plans as a comparison group, we found no evidence for a relative rise in crashes after 9pm on Mondays to Thursdays in 2005, or during an extended period from 2002 to 2005. These results are robust to alternative estimation strategies and controls. Our preferred estimates imply an upper bound in the odds ratio of crash risk associated with cell phone use of 3.0, which rejects the findings of most existing research including the 4.3 asserted in the influential paper by Redelmeier and Tibshirani (1997). A panel analysis of regional trends in cell phone ownership and legislation banning driver cell phone use confirms our basic result. We present possible explanations for this counterintuitive finding, and discuss implications for policy.

Traffic Crash Victimizations of California Children and Teenagers by Drinking Over-21 Drivers

Underaged drinking‖ by Californians younger than 21 generates perpetual concern, but the toll ―overaged drinkers‖ 21 and older inflict on children and teenagers has not been quantified. This study extracts Fatality Analysis Reporting System crash cases involving California drivers testing positive for alcohol use along with those of the other drivers, passengers, and nonoccupants in the same crashes for 1998-2007 and arranges them in cross tabulations showing the ages of drinking drivers in fatal crashes by ages, injury severity, and types of victims. National Highway Traffic Safety Administration estimates are used to project all alcohol-related traffic victimizations. Californians age 21 and older who drank and drove caused approximately 235,000 crashes from 1998-2007 victimizing persons under age 20, killing more than 400 children under age 16 and 400 teens age 16-19 and injuring nearly 80,000 children and teens. Drinking over-21 drivers caused most alcohol-related victimizations of teenage vehicle passengers and nonoccupants and victimized more sober teenage drivers than drinking teen drivers victimized sober over-21 drivers. If tabulated as a separate mortality cause, ―overaged drinking and driving‖ would be the fifth leading cause of death to California teens age 16-19 and the sixth leading cause for children ages 1- 15. The findings suggest ―overaged drinking‖ represents as severe a hazard to teenagers as ―underaged drinking.‖

Role of Poverty in California Teenagers’ Fatal Traffic Crash Risk

Teenagers’ high rates of motor vehicle crashes, accounting for 40% of external deaths among 16-19 yearolds, have been ascribed largely to inherent “adolescent risk-taking” and developmental hazards. However, the fact that compared to adults 25 and older, teenagers are twice as likely to live in poverty and low-income areas, risk factors for many types of violent death, has not been assessed. This paper uses Fatality Analysis Reporting System data on 65,173 fatal motor vehicle crashes by drivers in California’s 35 most populous counties for 1994-2007 to analyze fatal crash involvements per 100 million miles driven by driver age, county, poverty status, and 15 other traffic safety-related variables. Fatal crash rates were substantially higher for every driver age group in poorer counties than in richer ones. Multivariate regression found socioeconomic factors, led by the low levels of licensing and high unemployment rates prevalent in low-income areas, were associated with nearly 60% of the variance in motor vehicle crash risks, compared to 3% associated with driver age. The strong association between fatal crash risk and poverty, especially for young drivers who are concentrated in high-poverty brackets and low-income areas, suggests that factors related to poorer environments constitute a major traffic safety risk requiring serious attention.

Assessing the Link Between Environmental Concerns and Consumers’ Decisions to Use Clean-Air Vehicles

A consulting contract with the California Air Resources Board led to a project examining how California drivers’ and fleet managers’ perceptions, attitudes, and consumer behavior regarding Clean Vehicle Technologies influenced their own energy choices when it came to purchasing vehicles. The consultants examined archival research, conducted focus groups, and collected survey data to analyze participant attitudes and behaviors. Key to the success of the project was the use of instructional communication theory and practice, which enabled the consultants to work productively with the client in carrying out valid research and to evoke meaningful responses from the participants.

Survey explores teen driving behavior in Central Valley, Los Angeles high schools

Teenage drivers, particularly new drivers, have higher crash rates than adults. We surveyed 2,144 teenage drivers in California about their driving practices, factors influencing driving behavior, and views on driver education and resources. Teens wanted updated driver education courses and more behind-the-wheel training while learning to drive. They identified parents as their most important resource when learning to drive and also reported that parents were less likely to enforce the rule prohibiting driving with teen passengers than other driving rules. Teens described behavior by teen passengers that distracted them while driving. The findings indicate that new drivers benefit greatly from graduated driver licensing laws.