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56 A p p e n d i x B priority 1 Global Research Question 1: How Do Dynamic Driver Characteristics, as Observed Through Driver Performance Measures, Influence Crash Likelihood? These questions relate to how driver states (e.g., aggressive- ness, drowsiness, willingness to engage in distracting activ- ities) influence specific driver performance measures and subsequent crash likelihoods. This global research question represents 12 individual research questions: ⢠Can driving control performance for various states be catego- rized more simply (i.e., good and bad, or risky and nonrisky)? ⢠Can various driver states (e.g., drowsy, aggressive, distracted, engaged) be identified from naturalistic driving data? ⢠How do driver behavior and response influence subse- quent events and outcomes after a vehicle initially leaves the roadway? ⢠What is the relationship between measures obtained from pretest assessment batteries (e.g., a life stress test) and the frequency of engagement in distracting behaviors while driving? ⢠Does there appear to be any correlation between willingness to engage in distracting behaviors and life stress sources, per- sonality characteristics, or ability to focus attention? ⢠How often and under what circumstances do drivers drive while fatigued? ⢠What are the individual differences, both between and within drivers, related to fatigue? Fatigue sensors? ⢠How often and under what circumstances do drivers drive while under the influence of alcohol? ⢠What are the individual differences, both between and within drivers, related to alcohol use? Passive alcohol sensors? ⢠What are the differences in demographic data, test battery results, and performance-based measures between atten- tive and inattentive drivers? ⢠How might knowledge of demographic differences in atten- tive and inattentive drivers be used to mitigate the potential negative consequences of inattentive driving behaviors? ⢠Could information concerning demographic differences in attentive and inattentive drivers be used to improve driver education courses or traffic schools? Global Research Question 2: What Impacts Do Roadway Countermeasures Have on Lane-Keeping Performance? These questions relate to the effectiveness of roadway- based crash countermeasures on lane maintenance. This global research question represents 13 individual research questions: ⢠Are drivers more likely to lane keep on roadways with edge- line rumble strips? ⢠How do lane-edge markings affect lane keeping? ⢠What is the influence of rumble strips in measured lane- keeping performance? ⢠Are centerline rumble strips beneficial in improving lane- keeping performance? ⢠Would centerline rumble strips be effective in preventing head-on collisions? ⢠What is the influence of special curve warning markings (e.g., on-pavement markings)? ⢠What are the potential impacts of rumble strips on non- freeways? ⢠Would rumble strips be effective without the paved shoulder? ⢠Does rumble strip noise reduce the deviation from the lane, or does it function as an alarm to improve subse- quent alertness and lane keeping after encountering the rumble strip? ⢠Do rumble strips reduce the frequency and duration of lane deviations, making successful recovery more likely, Global Research Question Priorities
57 and/or does a lane departure over a rumble strip improve subsequent lane keeping and decrease the frequency of lane departures? ⢠How does the driverâs positioning of the vehicle affect lane keeping, and how is this related to the efficacy of edge marking and rumble strips? ⢠Are drivers less likely to pass with centerline rumble strips? ⢠How likely are drivers to overcorrect or countersteer away from edge rumble strips so that they avoid a road departure but encroach into an adjacent lane? Global Research Question 3: How Does Driver Distraction Influence Crash Likelihood? These questions relate to how driver distraction influences the likelihood of a driver being involved in a specific crash type (e.g., run-off-road (ROR), pedestrian, object, animal, and head-on crashes). This global research question repre- sents nine individual research questions: ⢠Is driving-control-performance pattern different for the same driver when distracted or not distracted (e.g., on cell phone or not on cell phone)? ⢠How do driver distractions affect involvement in ROR collisions? ⢠What is the role of inattention in collision risk at inter- sections? ⢠What is the role of driver inattention in rear-end crashes (i.e., striking a vehicle in the travel lane)? ⢠To what degree does the lead vehicle driver (i.e., the driver in the instrumented vehicle) contribute to the crash as a result of driver inattention? ⢠What is the role of driver inattention as it relates to crashes involving pedestrians, objects, or animals in the travel lane? ⢠What is the role of inattention (i.e., as a result of focusing on a secondary task) in lane-change or merge crashes? ⢠What is the role of inattention in head-on crashes? ⢠What is the role of inattention (i.e., as a result of focusing on a secondary task) in backing crashes? Global Research Question 4: How Do Aggressive Driving Behaviors Influence Crash Likelihood? These questions relate to the specific driver state of aggression and how this state leads to crash likelihood for specific crash types (e.g., ROR, backing, or rear-end crashes). This global research question represents 13 individual research questions: ⢠What is the relative contribution of aggressive driving to inappropriate gap acceptance? ⢠What is the relative contribution of aggressive driving to red light running? ⢠What is the role of aggressive driving in rear-end crashes (i.e., striking a vehicle in the travel lane)? ⢠To what degree does the lead vehicle driver (i.e., the driver in the instrumented vehicle) contribute to the crash as a result of aggressive driving? ⢠What is the role of aggressive driving as it relates to crashes involving pedestrians, objects, or animals in the travel lane? ⢠What is the role of aggressive driving (e.g., approach speed, gap with lead vehicle when change is initiated) in lane- change or merge crashes? ⢠What is the role of aggressive driving (e.g., speeding, being in a hurry) in backing crashes? ⢠What is the influence of aggression or aggressive driving on lane keeping? ⢠What is the influence of aggression or aggressive driving on ROR events? ⢠How does aggressive driving behavior affect crash risks? ⢠What is the role of aggressive driving in passing-maneuver errors? ⢠How does aggressive driving behavior affect near-crash risks? ⢠Why do aggressive driving behaviors occur, and how do they relate to ROR crashes and near crashes? Global Research Question 5: How Does Driver Fatigue Influence the Likelihood and Type of Crashes? This global research question represents six individual research questions related to fatigued drivers: ⢠What is the role of driver fatigue in rear-end crashes (i.e., striking a vehicle in the travel lane)? ⢠To what degree does the lead vehicle driver (i.e., the driver in the instrumented vehicle) contribute to the crash as a result of driver fatigue? ⢠What is the role of driver fatigue as it relates to crashes involv- ing pedestrians, objects, or animals in the travel lane? ⢠What is the role of driver fatigue in head-on crashes? ⢠What is the role of driver fatigue in lane-change or merge crashes? ⢠What is the role of driver fatigue in backing crashes? Global Research Question 6: How Do Advanced Driver Support Systems Influence Crash Likelihood? These questions relate to how advanced driver support systems (e.g., antilock braking system [ABS], adaptive cruise control [ACC], and collision-warning system [CWS]) influence the
58 likelihood of crash surrogate events. This global research ques- tion represents 23 individual research questions: ⢠Are drivers less likely to lose control with antilock braking systems? ⢠How do drivers react in a ROR crash or near crash in terms of precrash maneuvers (with or without a crash-warning system)? ⢠How do crash-avoidance systems, including electronic sta- bility control ESC, affect driver behavior in ROR or rear- end crash scenarios? ⢠Can ACC help reduce ROR crashes? ⢠What are the benefits of a CWS deployed in the fleet when a striking vehicle is in the travel lane? ⢠What are the benefits of other vehicle countermeasures (e.g., brake assist) in the fleet? ⢠Does vehicle CWS contribute to crashes? ⢠Do other types of vehicle countermeasures, such as brake assist, lead to struck secondary crashes? ⢠Given that most objects, pedestrians, and animals produce no radar signature, is there any indication that reliance on a CWS is a detriment? ⢠Are there benefits to enhanced vision systems at night (e.g., infrared headlamps or differing types of head lighting) in determining the presence of pedestrians or objects in the travel lane? ⢠Are there any forward CWS benefits related to head-on crashes? ⢠What are the potential benefits of other vehicle counter- measures (e.g., brake assist) in the fleet related to head-on crashes? ⢠What are the benefits of lane-change aids and a CWS? ⢠How does ACC use (compared with cruise control) affect speed compliance? ⢠How does ACC use affect eyes-off-the-road time (i.e., drivers allowing themselves to be more distracted)? ⢠Where do drivers look when they receive these alerts or activate these systems? ⢠How and how fast do drivers respond when they receive these alerts or activate these systems? ⢠Do these alerts and/or systems offer a safety benefit for impaired or drowsy drivers? ⢠What are the potential benefits of radar and ABS in reduc- ing the incidence and severity of automobile accidents? ⢠How do crash-avoidance systems, including ESC, affect driver behavior in ROR or rear-end crash scenarios? ⢠How can the effectiveness of back-up warning algorithms be tested? ⢠Are back-up warning systems of different types (e.g., cameras) beneficial? What aspects make them beneficial or detrimental? ⢠What is the driver response, in terms of immediate control input and subsequent speed selection, to in-vehicle CWS warnings? Global Research Question 7: What Is the Influence of Driver Impairment on Crashes and Driver Errors? These questions focus on the effect of the driver being in an impaired state on crash types and driving errors. This global research question represents eight individual research questions: ⢠What is the relative contribution of impairment to inap- propriate gap acceptance? ⢠What is the relative contribution of impairment to red light running? ⢠What is the role of driver impairment in rear-end crashes (i.e., striking a vehicle in the travel lane)? ⢠To what degree does the lead vehicle driver (i.e., the driver in the instrumented vehicle) contribute to the crash as a result of other driver impairment? ⢠What is the role of other driver impairment as it relates to crashes involving pedestrians, objects, or animals in the travel lane? ⢠What is the role of other driver impairment in head-on crashes? ⢠What is the role of other driver impairment in lane-change or merge crashes? ⢠What is the role of other driver impairment in backing crashes? Global Research Question 8: How Does the Turn-Lane Configuration Influence Behavior and Crash Risks? These questions relate to how intersection negotiation per- formance is influenced by roadway (specifically intersection) traits. This global research question represents seven indi- vidual research questions: ⢠What are the safety effects of protected and unprotected turn lanes? ⢠How do turn lanes change the pattern of conflict at inter- sections? ⢠Do offset left-turn lanes (bays) affect turn behavior (e.g., gap acceptance and the decision to turn)? ⢠How much do left-turn lanes and/or signal phases reduce collision risk? ⢠How much do left-turn lanes reduce collision risk, with and without left-turn signal phases? ⢠How much do right-turn lanes reduce collision risk, with and without right-turn signal phases? ⢠How much do right-turn lanes and/or signal phases reduce collision risk?
59 Global Research Question 9a: What Variables or Pre-Event Factors Are the Most Effective Crash Surrogate Measures? These questions relate to different factors or events that can be used as crash surrogate measures most effectively. This global research question represents eight individual research questions: ⢠For a given crash type, are any conflicts directly informa- tive about crashes in the sense that they are generated from similar sets of background conditions? ⢠Which noncrash incidents can be used as crash surrogates to assess risk for road-departure crashes? ⢠Do naturalistic driving data contain measurable episodes of disturbed control? (Broad research question.) ⢠Do objective measures of disturbed control from natural- istic driving data, together with highway geometric factors, off-highway factors, and environmental factors, satisfy cri- teria for crash surrogates, that is, are they related to actual crashes? (Broad research question.) ⢠If so, are these conflicts more frequent, as frequent, or less frequent than actual crashes? ⢠Once a road departure occurs, what is the next most com- mon sequence of incidents and outcomes (e.g., safe recov- ery and return to roadway, minor conflict with safe return, near miss with safe return, property damage accident, or injury accident)? ⢠Once a road departure occurs, what kinematic variables can be used to define the different outcomes (e.g., road- departure crash, near crash, conflict, or incident)? ⢠What measures exist in naturalistic driving data that directly measure disturbed control? Global Research Question 9b: What Explanatory Factors Are Associated with Crashes or Crash Surrogates, and What Analytical Models Can Be Developed to Predict Crashes or Crash Surrogates? These questions relate to different factors that can be effec- tively associated with crashes and crash surrogates. This global research question represents 14 individual research questions: ⢠What kinematic measures of driving control performance are available in the naturalistic driving data, and what are the levels of accuracy in those measures? ⢠What kinematic variables can be used to determine when a road departure is likely or imminent? ⢠How can severity-related factors conditioned on an event having occurred be most effectively examined? ⢠Are other driving control metrics necessary (in addition to vehicle kinematic measures) to identify disturbed control? ⢠Are there measures of driving control performance in existing FOT data that depend on highway factors in a way that is consistent with single-vehicle road-departure crash frequencies? ⢠What factors are associated with unconditional event occurrences? ⢠What is the nature of the relationship between crashes, near crashes, incidents, and pre-event maneuvers and pre- cipitating factors, driver factors, contributing factors, and environmental factors? ⢠For a given crash type and data source, is it possible to identify a plausible structural model? If so, is the data source sufficiently rich to support estimation of the values taken on by the model variables for crashes and interesting noncrashes? ⢠If it is not possible to identify and validate plausible models, what additional data would be needed to support the esti- mation of values for crashes and interesting noncrashes? ⢠What hierarchical structure (statistically speaking), if any, exists in the manner in which these relationships need to be explored? ⢠Do single-vehicle road-departure crashes occur only under conditions of disturbed control? (Broad research question.) ⢠Can satisfactory crash risk predictions be made based on vehicle, driver, and highway factors available from natu- ralistic driving data (e.g., via extreme value theory), or do additional roadside and environmental factors need to be introduced? ⢠Does coupling roadside factors to naturalistic driving data improve correlation with actual crashes? ⢠What kinds of elucidative evidence emerge from the analy- sis of roadway departure crashes in terms of the relationship between crashes, near crashes, and incidents with situational factors, and what (statistical) hierarchical structure exists within these relationships? priority 2 Global Research Question 10: How Do Roadway Features Influence Crash Likelihood? These questions are similar to those in Question 14, except that this set of questions relates roadway features to crash surrogates. This global research question represents 15 indi- vidual research questions: ⢠What statistical tests are available to determine if measures of driving control performance in naturalistic data and single-vehicle crashes depend on geometric features in a consistent way?
60 ⢠What key driver, roadway, and environmental factors affect lane keeping that may result in a road departure? ⢠What is the influence of life events and factors on ROR events? ⢠What combination of driver, vehicle, traffic, environmen- tal, and roadway factors leads to rear-end crashes (i.e., striking a vehicle in the travel lane)? ⢠What environmental factors influence whether a vehicle actually departs the roadway once a road departure is precipitated? ⢠To what extent do roadway features influence whether a vehicle actually departs the roadway once a roadway depar- ture is precipitated? ⢠How frequently do road departures occur given a specific set of roadway variables? ⢠Are any specific highway features (e.g., isolated horizontal curves, sharp horizontal curves, sequences of horizontal curves, and combinations of horizontal and vertical curves) associated with single-vehicle road-departure crashes and specific driving control performance measures? ⢠How is the occurrence of ROR events under different driv- ing conditions and roadway geometries related to ROR causal factors and driver inputs during ROR maneuvers? ⢠How are ROR crashes affected by different roadway geom- etries (e.g., shoulder width)? ⢠How are ROR crashes and near crashes affected by differ- ent roadway features (e.g., shoulder width, signage, and delineators)? ⢠What is the influence of roundabouts on pedestrian crashes? ⢠Are there methods of identifying potentially dangerous intersections before the occurrence of high collision rates? ⢠What is the role of curves and grades in lane-change or merge crashes? ⢠What is the role of length and type of ramps (e.g., weave) in lane-change or merge crashes? Global Research Question 11: How Do Signage, Lighting Conditions, and Other Traffic ControlâRelated Countermeasures Influence Crash Likelihood and Driver Performance? These questions relate to the effect that pavement markings, signage, reflectors, and other traffic control devices have on both driver performance variables and on the likelihood of crash surrogate events. This global research question repre- sents 26 research questions. Traffic Control SignalâRelated Questions ⢠Would there be any safety benefits of alternative signal- control strategies? Adaptive signal-control timing? Alter- native signal timing? ⢠How do traffic control variables influence braking behav- ior at intersections? ⢠How do traffic control variables influence speed behavior at intersections? ⢠How do traffic control variables influence compliance with traffic controls at intersections? ⢠What is the influence of closed-loop signal systems? ⢠What is the safety effect of offset, split, and cycle time for fixed-time signals? ⢠What is the safety effect of detector placement and signal- timing parameters for semiactuated signals? ⢠What are the safety effects of different-sized signal heads (8 in. versus 12 in.), number of signals per approach lane (is one necessary for each lane?), and signal placement (over- head versus nearside)? ⢠How does operating speed affect deceleration for traffic signals? ⢠How do drivers react to different intersection signal instal- lations (phasing and timing operations)? Do certain types appear better? ⢠What are the effects of protected left-turn phasing at high- speed rural intersections? ⢠What is the prevalence of straight crossing path traffic sig- nal violations? ⢠Do traffic control devices countermeasures (e.g., signal phase related) lead to struck secondary crashes? Other Questions ⢠How does signage influence braking behavior at intersec- tions? ⢠Are road departures less likely when pavement markings are more visible? ⢠Does roadway lighting result in fewer nighttime road departures? ⢠Does signage have any impact on frequency of road depar- tures (e.g., large chevrons may alert drivers to an adverse horizontal curve)? ⢠What are the effects of in-pavement warning lights at pedestrian crossings? ⢠What is the effectiveness of various countermeasures (e.g., strobe lights to red lights) to reduce intersection-related crashes? ⢠Could new technology, such as automated all-red signal extension systems, infrastructure to inform drivers of acceptable gaps in traffic, or dilemma-zone detection at high-speed intersections, reduce intersection crashes? ⢠How do traffic control variables influence gap acceptance at intersections? ⢠How does signage influence gap acceptance at intersections? ⢠What are the benefits of roadway lighting, and under what circumstances does roadway lighting increase driversâ
61 ability to see pedestrians, animals, or objects in the travel lane? ⢠What are the benefits of reflectors and reflective clothing, and under what circumstances do these items improve driversâ ability to see pedestrians, animals, or objects in the travel lane? ⢠How long does it take for drivers to respond to speed limit reductions? ⢠Are drivers influenced by speed reduction signs, and if so, how? Do drivers travel at higher speeds on secondary streets and highways after long-distance travel on freeways? priority 3 Global Research Question 12: How Do Static Driver Characteristics Influence Crash Likelihood? These questions relate to individual driver traits (e.g., age, gender, and personality) and how they influence crash likeli- hoods. They also address the ability to distinguish between safe and unsafe drivers. This global research question repre- sents seven individual research questions: ⢠What can be done to reduce the number of crashes and fatalities for older drivers? ⢠What is the influence of gender on ROR crashes? ⢠What is the influence of age on ROR crashes? ⢠What is the influence of personality (as measured by MyersâBriggs or other assessment) on ROR crashes? ⢠What is the influence of driving confidence (self-report) on ROR crashes? ⢠What is the influence of useful field of view on ROR crashes? ⢠Do demographics play a role in ROR crashes? priority 4 Global Research Question 13: How Do Static Driver Characteristics, as Observed Through Driver Performance Measures, Influence Crash Likelihood? These questions relate to individual driver traits (e.g., age, gen- der, and personality) and how they influence specific driver performance measures and subsequent crash likelihoods. These questions also address the ability to distinguish between safe and unsafe drivers. This global research question represents 41 individual research questions: Age and Gender ⢠Does the relative risk of different intersection maneuvers vary with driver age and gender? ⢠Do older drivers make fewer left turns or accept larger gaps? ⢠Do older drivers make fewer right turns or accept larger gaps? ⢠How do drivers of various age categories judge and select a gap in traffic flow to enter or cross a street or highway? ⢠How do differences in age, gender, and other driver traits influence variations in driving behavior? ⢠How do drivers of various age categories use the available acceleration lanes when entering freeways? ⢠What is the level of compliance by drivers of various age categories to stop signs, traffic signals, advisory speeds on curves, speed limits, and stopping for pedestrians? ⢠What is the relationship between driversâ involvement in crashes, near crashes, and incidents and driversâ age, driv- ing knowledge, vision, driving experience, and vehicle familiarity? ⢠What are exposure differences in terms of road types, speed selection, and miles traveled across driver age and gender subgroups? ⢠What are the behavioral characteristics, especially in terms of driving style and visual search, which distinguish the young- est and oldest drivers from drivers aged 25 to 65 years? ⢠What is the influence of gender on lane keeping? ⢠What is the influence of age on lane keeping? Other Questions ⢠In terms of elucidative evidence, what types of behavioral correlates emerge? For example, are attitudinal measure- ments indicative of revealed behavior in terms of headway maintenance and speed reductions? ⢠Are attitudinal (e.g., predisposing) measurements indica- tive of revealed behavior in terms of headway distance and speed reduction? ⢠Is there a difference in the driving control performance of good and bad drivers (or risky and nonrisky drivers) at locations with geometric features associated with high single-vehicle crash frequency? ⢠How does within- and between-subject variation in lane keeping compare (i.e., to what extent does one driver con- sistently perform better than another driver)? ⢠How can performance differences be quantified (e.g., as differences in the frequency and amplitude of steering and braking actions; or in terms of the frequency, dura- tion, or amount of lane departure, time to departure, or other measures)? ⢠Are all drivers equally exposed to road departures? ⢠How do driver testing scores serve as predictors to driving performance, in particular, to lane keeping? ⢠What is the role of driver factors in the risk associated with inappropriate gap acceptance with crossing traffic? ⢠What is the role of driver factors in the risk associated with red light running and inappropriate gap acceptance situations?
62 ⢠What are the intra- and interindividual differences in braking and crash-avoidance skill? ⢠What are the intra- and interindividual differences in will- ingness to pass and skill in passing? ⢠What are the intra- and interindividual differences in lane- change or merge behavior and skill? ⢠What are the intra- and interindividual differences in backing behavior and skill? ⢠What is the influence of personality (as measured by MyersâBriggs or other assessment) on lane keeping? ⢠What is the influence of driving confidence (self report) on lane keeping? ⢠What is the influence of risk-taking propensity on lane keeping? ⢠What is the influence of experience and previous motor vehicle accidents on lane keeping? ⢠What is the influence of life events and factors on lane keeping? ⢠What is the influence of experience and previous motor vehicle accidents on ROR crashes? ⢠Do demographics influence lane keeping? ⢠How do drivers adjust their behavior (relative to expected adjustments) in response to high-risk situations? Such situations may be environmental (e.g., night, slick roads from rain and snow, or fog) or personal (e.g., fatigue or alcohol intoxication). ⢠How do exposure differences across subgroups vary in terms of amount of travel and environment? ⢠How does the driving experience vary in different regions of the country and for different drivers? ⢠What driving styles exist across the country and within dif- ferent driving conditions? ⢠How often, for what length of time, and in what pattern do drivers look away from the forward roadway? What are the individual differences among and between drivers? ⢠Can attitudes toward risk taking (or other behaviors or beliefs) versus driving style (i.e., errors, inattention, or dis- traction) be characterized demographically? ⢠How are a specific driving behavior and crash risk affected by both permanent descriptors (e.g., age, gen- der, driving experience, and crash record) and transi- tory descriptors (e.g., fatigue, other impairment, and distraction)? ⢠How do safe and unsafe drivers differ in demographic data, test battery results, and performance-based mea- sures? What are the crash rate and history of violations before the study for these safe and unsafe drivers? (Some drivers may not be honest in reporting this driving his- tory information.) ⢠What is the relationship between various risky driving behaviors and combinations of risky driving behaviors between low-risk and high-risk drivers? Global Research Question 14: What Are the Relationships Between Driver Behavior, Performance, Crash Types, Crash Likelihood, and Population-Attributable Risk for Each Factor Contributing to Crashes? These questions relate to how driver behavior, driving perfor- mance, and population-attributable risk contribute to crashes and crash likelihoods. This global research question represents 62 individual research questions: ⢠In order to use conflict data to predict crash probability, it is necessary to know how the selected evasive action varies as a function of background conditions. For a given crash type and data set, is it possible to identify and validate plausible models for this relationship? ⢠In terms of elucidative evidence, what types of behavioral correlates emerge? ⢠What exposure variables are available and which are the best measures to use in the analytical models? Possible exposure variables include traffic volume, traffic density, driver subpopulations (i.e., crash risk for teenage drivers compared with older drivers), and miles of travel. ⢠What driver actions and behaviors are present in the sec- onds preceding and during ROR crashes? ⢠Can ROR countermeasures be effectively designed to reduce crashes? ⢠At what point can the intersection safety effectiveness of automated speed enforcement on roads with posted speed limits be considered credible? ⢠What is the role of illegal maneuvers in collision risk at intersections? ⢠What driver actions occur in the seconds preceding and during intersection crashes and near crashes? ⢠What is driversâ situational awareness just before crashes (e.g., at multiple-vehicle accidents at intersections)? ⢠What is the role of driver factors in the risk associated with red light running and inappropriate gap acceptance situations? ⢠What is the relative risk of different maneuvers at inter- sections? ⢠Having defined appropriate exposure measures for each intersection maneuver, what is the relative risk of the dif- ferent maneuvers? ⢠How does risk assessment vary based on driver behavior and intersection design? ⢠What effect does the intersection environment have on the driverâs decision-making processes? ⢠How does the public perception of the attitude of law enforcement on highway safety affect intersection crashes? ⢠Is there greater risk for left turns?
63 ⢠What is the role of driver factors in the risk associated with inappropriate gap acceptance with opposing traffic on left turns? ⢠What is the role of driver factors in the risk associated with inappropriate gap acceptance with opposing traffic on right turns? ⢠What is the relative contribution of decision errors to inappropriate gap acceptance? ⢠What is the relative contribution of illegal maneuvers to inappropriate gap acceptance? ⢠What is the relative contribution of decision errors to red light running? ⢠What is the role of driver factors in the risk associated with red light running? ⢠What is the relative contribution of illegal maneuvers to red light running? ⢠For willful straight crossing path signal violations, what is the nature (e.g., position and speed) of the crossing traffic? ⢠What is the role of following distance in rear-end crashes (i.e., striking a vehicle in the travel lane)? ⢠To what degree does the lead vehicle driver (i.e., the driver in the instrumented vehicle) contribute to the crash as a result of the following distance? ⢠What is the role of following distance as it relates to crashes involving pedestrians, objects, or animals in the travel lane? ⢠What is the role of sight distance in passing maneuver errors? ⢠How many times do drivers pass against road markings (e.g., double yellow)? ⢠How many times do drivers misjudge the speed or gap of approaching vehicles? ⢠How many times do drivers misjudge car acceleration or time available? ⢠What is the role of inadequate mirror check in lane-change or merge crashes? ⢠What is the role of no blind-spot check in lane-change or merge crashes? ⢠What is the role of inadequate gap in lane-change or merge crashes? ⢠What is the role of failure to match speed in lane-change or merge crashes? ⢠What is the role of failure to recognize speed differential in lane-change or merge crashes? ⢠What is the role of sight distance in lane-change or merge crashes? ⢠What is the role of failure to visually verify (i.e., over-the- shoulder check)? ⢠What is the role of inadequate mirror check in backing crashes? ⢠What is the role of failure to clear windows or improve visibility in backing crashes? ⢠What is the influence of factors such as backing while turning? ⢠What mechanisms of occupant injury exist that have been unrecognized or underemphasized? ⢠What baselines can be measured in frequencies, risk expo- sure, or behaviors against which design improvements can be compared? ⢠How does driver interaction with vehicle systems change over extended periods (e.g., 1 year)? ⢠What steering and brake inputs occur in the seconds pre- ceding collisions? ⢠What is the influence of useful field of view on lane keeping? ⢠What is the driver reaction time and control input selec- tion for safety-critical events? ⢠What is the error/accident involvement in crashes, near crashes, and incidents, and how can the driver behavior that contributed to the involvement be assessed? ⢠What are the response times, deceleration, braking behav- ior, and turn-signal use of following drivers in response to vehicles that enter the forward driving path? ⢠How can braking and signaling behaviors with respect to striking and struck drivers be assessed and analyzed? ⢠How can potential patterns in the driving performanceâ based measures (e.g., high longitudinal decelerations, high lateral accelerations) be assessed and analyzed? ⢠What new methodologies for assessing the role of human factors in accident causation can be developed? ⢠What driver behaviors (e.g., bracing, postural adjust- ments) arise immediately before a crash? ⢠What is the role of following distance in lane-change or merge crashes? ⢠What types of accidents occur when drivers are paying attention? ⢠In what circumstances do distracted drivers have acci- dents (e.g., are these more likely within the influence area of intersections or in stop-and-go traffic, but less likely on freeways)? ⢠How can differences between struck and striking vehicles with regard to sampling behavior for rear-view and side- view mirrors be assessed and analyzed? ⢠Does a driverâs familiarity with a road influence his or her driving behavior? ⢠How do differences in vehicle types influence variations in driving behavior? ⢠What factors initiate or influence the sequence of events resulting in a motor vehicle accident? ⢠How does the availability or lack of sight distance affect how a driver travels over a crest, around a horizontal curve, or through an intersection? ⢠In a crash or near crash did the driver perceive but mis- judge the available gap, or did the driver not perceive the oncoming vehicle?
64 Global Research Question 15: How Do Individual Differences (e.g., Age, Gender, or Speed Selection) Influence Lane-Keeping Performance? These questions relate to the influence of individual differ- ences on lane maintenance. This global research question represents five individual research questions: ⢠What are the individual differences in lane-keeping per- formance? ⢠What is the role of speed relative to the posted speed limit in lane-keeping performance? ⢠Does lane keeping vary with vehicle type or driver age and gender? ⢠How do driver age and gender, grade, curve, speed, rumble strips, and other factors relate to lane-keeping performance? ⢠How does driver behavior (speeding) affect lane keeping? Global Research Question 16: How Do Traffic and Traffic Volume Influence Intersection Negotiation, Lane-Keeping Performance, and Crashes? These questions relate to how different crash surrogate events and driving maneuvers are influenced by the traffic volume and specific vehicles (potentially conflict vehicles) within proximity of the instrumented vehicle. This global research question represents 16 individual research questions: ⢠Is the illustrative hierarchy of relationships generalizable to other nonintersection crash types such as leading vehi- cle crashes? ⢠Does risk of lane departure vary by road type and traffic volume? ⢠How will increased traffic volume on U.S. roadways affect driver involvement in ROR crashes? ⢠What is the influence of surrounding traffic on lane keeping? ⢠Does opposing traffic affect lane position or lane-keeping performance? ⢠What is the influence of adjacent traffic or opposing traffic on lane keeping? ⢠What is the influence of leading vehicles on lane keeping? ⢠What lane-changing behavior of nearby vehicles may con- tribute to crash and near-crash events? ⢠How can a consideration of traffic volume for each of the turning maneuvers, which may play a role in all aspects of intersection risk, be incorporated into the analysis? ⢠What is the relationship of traffic density and type of traffic- control devices to crash occurrence at intersections? ⢠How does the pattern of conflicts and collision risk vary with traffic volume? ⢠How does traffic volume influence left-turn maneuvers at intersections? ⢠How does traffic volume influence right-turn maneuvers at intersections? ⢠What is the role of the amount and location of traffic in lane- change or merge crashes? ⢠What combinations of factors (including closure speed) affect left-turn risk? ⢠What combinations of factors (including closure speed) affect right-turn risk? priority 6 Global Research Question 17: Do Vehicle Characteristics Influence Crash Likelihoods or Driver Behaviors? These questions relate to specific vehicle factors (e.g., size, cen- ter of gravity, and kinematic measures) and how they influence crash likelihoods and driver behaviors. This global research question represents eight individual research questions: ⢠Are sport utility vehicles more likely to be involved in an overturn than other passenger vehicles? ⢠Are vehicle kinematic measures sufficient to identify dis- turbed control for risk measures in single-vehicle departure crashes? ⢠How do vehicle characteristics (e.g., size, braking capa- bilities, and center of gravity) affect subsequent events and outcome after a vehicle initially leaves the roadway? ⢠How do circumstances of low friction (e.g., OBD II, trac- tion control, and wheel slip) affect driver behavior and crash or near-crash risk at intersections? ⢠Does driver behavior or performance relate to vehicle design (e.g., weight, center of mass, greenhouse geometry, and instrument panel design)? ⢠What lifestyle or driving behaviors (e.g., gas use, brake behavior, and trip distances) reveal opportunities for fuel economy or alternative-fuel vehicle designs? ⢠What are the kinematic conditions, in terms of range, range rate, vehicle speed, and deceleration, at the onset of a hard braking maneuver? ⢠How does driver behavior change by vehicle type (e.g., truck or SUV)? Global Research Question 18: What Are the Interrelationships of Environmental, Road, and Driver Factors with Nondriving-Related Activities (e.g., Technology, OEM, or Nomadic Devices)? These questions relate to relative risk of specific driving situ- ations or behaviors when drivers are engaged in nondriving-
65 related tasks (e.g., original equipment manufacturer [OEM], technology, or nomadic devices). This global research ques- tion represents 19 individual research questions: ⢠What is the relative risk of an activityâs duration on driver behavior when using technology-related tasks? ⢠What is the relative risk of an activityâs duration on driver behavior when using OEM system tasks? ⢠What is the relative risk of an activityâs duration on driver behavior when using nomadic devices? ⢠What is the relative risk of the road geometry (e.g., curves, straightaways, and hills) on driver behavior when using technology-related tasks? ⢠What is the relative risk of the road geometry on driver behavior when using OEM system tasks? ⢠What is the relative risk of the road geometry on driver behavior when using nomadic devices? ⢠What is the relative risk of time of day on driver behavior when using technology-related tasks? ⢠What is the relative risk of time of day on driver behavior when using OEM system tasks? ⢠What is the relative risk of time of day on driver behavior when using nomadic devices? ⢠What is the relative risk of traffic density on driver behav- ior when using technology-related tasks? ⢠What is the relative risk of traffic density on driver behav- ior when using OEM system tasks? ⢠What is the relative risk of traffic density on driver behav- ior when using nomadic devices? ⢠What is the relative risk of pedestrian or cyclist density on driver behavior when using technology-related tasks? ⢠What is the relative risk of pedestrian or cyclist density on driver behavior when using OEM system tasks? ⢠What is the relative risk of pedestrian or cyclist density on driver behavior when using nomadic devices? ⢠What is the relative risk of weather conditions on driver behavior when using technology-related tasks? ⢠What is the relative risk of weather conditions on driver behavior when using OEM system tasks? ⢠What is the relative risk of weather conditions on driver behavior when using nomadic devices? ⢠What is the relative risk of various sources of currently available and future devices (e.g., nomadic or in-vehicle devices such as iPhones or mobile offices)? Global Research Question 19: How Does Seatbelt Use Vary with Different Levels of Enforcement and in Different Jurisdictions? These questions are specifically related to the use of seatbelts across jurisdictions and how such use changes as the laws related to seatbelt usage change. This global research ques- tion represents two individual research questions: ⢠How does seatbelt use vary between states with and with- out primary seatbelt laws? For example, do different types of seatbelt laws result in variations of seatbelt use in the presence of passengers or during day and night hours? ⢠What is the effect on seatbelt use of a change in seatbelt law from a secondary to a primary source? priority Unranked Global Research Question 20: General or Very High-Level Questions This category of questions represents very high-level (non- specific) research questions. This global research question represents 23 individual research questions: ⢠What driver, vehicle, operational, roadway, and environ- mental factors increase inadvertent lane departures? Spe- cific factors of interest (*denotes highest-priority factors): driver fatigue, speed limit, alcohol level, driver distraction, driver gender, shoulder width, shoulder type (paved or unpaved) clear zone cross slope, weather, day or night, *driver age, *vehicle speed, *lane width, edge drop pres- ence, *lane line presence and nighttime visibility, *rumble strip presence, *curvature. ⢠What percentage of roadway-departure crashes start as rear-end crash scenarios? ⢠What combination of driver, vehicle, traffic, environmen- tal, and roadway factors leads to rear-end crashes in which there is a struck vehicle in the same travel lane? ⢠What combination of driver, vehicle, traffic, environmen- tal, and roadway factors leads to crashes involving pedes- trians, animals, or objects in the travel lane? ⢠What combination of driver, vehicle, traffic, environmen- tal, and roadway factors leads to head-on crashes? ⢠What combination of driver, vehicle, traffic, environmental, and roadway factors leads to lane-change or merge crashes? ⢠What combination of driver, vehicle, traffic, environmen- tal, and roadway factors leads to backing crashes? ⢠How do various factors work together to affect collisions, and how do exposure data for noncrash populations and accurate precrash data weigh into this scenario? ⢠How are a specific driving behavior and crash risk affected by both permanent descriptors (e.g., curvature, road sur- face, lane width, and sight distance) and transitory descrip- tors (e.g., weather, light conditions, traffic flow, and adjacent vehicles)? ⢠What effect do various countermeasures have on crash and near-crash incidents?
66 ⢠Where do drivers position their vehicles in the travel lane on two-lane and two-way roads (using a simply painted centerline and gravel shoulders as baseline), and is this position influenced by factors such as opposing traffic volumes, centerline rumble strips, shoulder treatments, curbs, and weather? ⢠What is the interrelationship of driver factors and behavior with roadway design and traffic conditions on the risk of collision and causalities? ⢠How cost effective are various countermeasures? ⢠What is the relative frequency of these driver factors and their causal contribution within a defined accident and driving population? ⢠What is the feasibility and research potential of linking GIS and GPS data to investigate ROR crashes? ⢠What defined events may be recorded through naturalistic driving studies so that these events may be understood? ⢠For the purpose of accident prediction modeling, how can driversâ failures to perceive oncoming vehicles be classified, and what are the baseline estimates of the frequency of such events? ⢠What opportunities for crash countermeasures exist that have been unrecognized or underemphasized? ⢠How can crash data from the 100-car naturalistic driving study be used to investigate the potential role of specific crash-avoidance systems in preventing near crashes and actual crashes? ⢠How do drivers process multiple sources of information? ⢠How do drivers make decisions? ⢠What types of driver distraction episodes can be identified and understood? ⢠What problems emerge from an examination of naturalistic driving data that would be amendable to countermeasures? Global Research Question 21: How Else Can Naturalistic Driving Data Be Used? These questions relate to how naturalistic driving data can be used to address other questions, including how roadside factors can be integrated with the naturalistic driving data. This global research question represents 10 individual research questions: ⢠Can the analysis of data in southeast Michigan be applied or recreated in another region, such as Virginia? ⢠Can roadside factors (e.g., locations of poles, trees, bridge abutments, and side slopes) be coupled to naturalistic driving data? ⢠Can general descriptors of roadside environments be used in this coupling (e.g., tree density or proportion of side slope steeper than 4:1), or does the location of roadside obstacles need to be more specified? ⢠Could naturalistic driving data be used to validate simulators? ⢠Can a cognitive model be developed that could assess how specific factors influence specific driving tasks or events (e.g., gap acceptance or ROR events)? ⢠How can human factors design standards be implemented in roadway design to minimize errors associated with gap acceptance or other driving behaviors? ⢠What is the incidence of drowsiness and conditions under which drowsiness arises? ⢠How can lane-change events be classified according to sub- ject vehicle, role, event severity, precrash or event maneu- vers, causal or contributing factors, evasive maneuvers, and state variables? ⢠How can taxonomy development and group identification concepts be used to define and identify problem driver types and actions (specifically, alcohol-impaired drivers and the driving performance mistakes made by particu- lar types of alcohol-impaired drivers under certain condi- tions), and how can this process lead to recommendations for dealing with particular classes of drivers? ⢠Can a design driver be defined, and relative to that concept can crash causes be identified? Global Research Question 22: How Does the Speed That Drivers Select Influence Other Driver Behaviors or Actions? These questions relate to speed selection and how a driverâs speed selection is guided by other factors and behaviors and vice versa. This global research question represents nine indi- vidual research questions: ⢠Do drivers adjust their headway distance in response to level of operating speed, traffic volumes, weather condi- tions, road conditions, and visibility? ⢠How does pavement roughness affect speed (i.e., how much will milled pavement slow drivers down)? ⢠Do drivers drive faster and/or wander less in the lane on curves with better delineation (e.g., brighter lane mark- ings, RPMs, chevrons, post-mounted delineators) than on curves with poorer delineation? ⢠How do drivers select speed? ⢠Is a subset of drivers responsible for the majority of speed- ing, or do all drivers speed occasionally? ⢠Do drivers travel at slower speeds and with longer head- ways, and to what degree, in rain, snow, or fog? ⢠Does speed increase with cell phone usage? ⢠Do drivers travel at slower speeds and within what range when pedestrians (especially children) and bicyclists are present? ⢠What factors (e.g., roadway geometry, roadside features, intersections, driveways, weather, traffic volume, or day versus night) influence a driverâs choice of operating speed, and how does the speed change?
67 Global Research Question 23: How Do Roadway Features Influence Driver Performance and Behavior? These questions relate to the effect that specific roadway fea- tures (e.g., rumble strips or glare from lighting) have on driver performance and behavior. This global research question rep- resents 21 individual research questions: ⢠How much impact does pavement surface condition have on driversâ ability to safely recover within their own lane once a road departure is likely? ⢠What is the influence of superelevation on lane keeping and departure? ⢠How do lane keeping and road departure on curves and grades compare with straight and flat road segments? ⢠What are the effects of closely associated versus isolated curves with the same geometric characteristics, such as spi- rals, and other compound curves on lane keeping? ⢠What are the potential effects of improved roadway delin- eation? ⢠How do rumble strips change driver behavior? ⢠Are current design guidelines for roadway design (e.g., cur- vature of roadway) appropriate for the aging population? ⢠How does risk assessment vary based on driver performance and highway design or other features in roadway departure? ⢠How does roadway design influence compliance with traf- fic controls at intersections? ⢠What is the effect of removing access (e.g., commercial driveways) near high-volume signalized intersections? ⢠What effect do access points near the intersection have? ⢠How does sight distance affect safety at intersections? At roundabouts? Of pedestrians? ⢠How does roadway design influence speed behavior at intersections? ⢠How does roadway design influence braking behavior at intersections? ⢠How does roadway design influence gap acceptance at intersections? ⢠What is the influence of factors such as backing on a slope? ⢠How do differences in roadway geometry influence varia- tions in driving behavior? ⢠What road features (e.g., generally gentle curvature with the exception of one curve) and curve features (e.g., tight radius but high posted speed, wide shoulders) result in high lateral acceleration? ⢠What is the effect of glare from opposing vehicles and roadway lighting of differing levels on driver behavior and performance? ⢠How does the length of an acceleration lane and traffic vol- ume affect how long drivers take to merge or change lanes? ⢠At what point on the ramp do drivers typically merge? Global Research Question 24: How Do the Number and Type of Passengers Influence the Driverâs Behavior? These questions relate to investigating how passengers influ- ence driving behavior and the effect of multiple passengers. This global research question represents three individual research questions: ⢠How do driving behavior and crash and near-crash risk change when one or more passengers are present? ⢠How does a driverâs behavior change with and without particular passengers, such as peers, parents, and children, in the vehicle? ⢠Does teen driver behavior change based on the presence of other teens in the vehicle? Global Research Question 25: How Does Driver Fatigue Affect Driver Performance? These questions relate to investigating how driver fatigue affects driving performance. This global research question represents four individual research questions: ⢠How does fatigue influence speed behavior at intersections? ⢠How does fatigue influence braking behavior at inter- sections? ⢠How does fatigue influence compliance with traffic controls at intersections? ⢠How does fatigue influence gap acceptance at intersections? Global Research Question 26: How Does Inattention Affect Driver Behavior and Performance? These questions relate to the specific driver state of being inattentive and how it affects driving behavior, as well as how roadway and environmental factors influence driver inatten- tion. This global research question represents 51 individual research questions: ⢠How do driver factors such as inattention or fatigue affect lane keeping? ⢠How does signage influence inattention at intersections? ⢠How do traffic control variables influence inattention at intersections? ⢠How does roadway design influence inattention at inter- sections? ⢠How does fatigue influence inattention at intersections? ⢠What is the role of inattention in intersection errors and conflicts? ⢠How does distraction influence braking behavior at inter- sections?
68 ⢠How does distraction influence speed behavior at inter- sections? ⢠Does driver distraction influence compliance with traffic controls at intersections? ⢠How does distraction influence compliance with traffic controls at intersections? ⢠To what degree do different types of distractions influence inattention at intersections? ⢠What is the relative contribution of inattention to in- appropriate gap acceptance? ⢠How does distraction influence gap acceptance at inter- sections? ⢠What is the relative contribution of inattention to red light running? ⢠How do drivers come to use and understand advanced in-vehicle safety systems, and are the full benefits of the system being realized by individual drivers? ⢠What is the frequency and type of in-vehicle activity related to the use of OEM system tasks? ⢠What is the level of exposure for OEM system tasks? ⢠What types of technology-related tasks do drivers engage in while driving, and at what frequency? ⢠What nontechnology-related tasks do drivers engage in while driving? ⢠What in-vehicle activities do drivers engage in using nomadic or non-OEM devices? ⢠What external distractions (e.g., billboards, variable mes- saging signs, pedestrians, animals, objects, and other traf- fic) influence driving behavior? ⢠What is the level of exposure for technology-related tasks? ⢠What is the level of exposure for nomadic devices? ⢠What is the level of exposure for external distractions? ⢠How frequently do drivers interact with infotainment or nomadic devices (e.g., iPod)? ⢠Is the frequency of use for infotainment or nomadic devices affected by road type and/or traffic volume? ⢠Is the frequency of use for infotainment or nomadic devices affected by lead vehicles? ⢠How long are the interactions of use for infotainment or nomadic devices? ⢠What are the eyeglance patterns before, during, and after interactions of use for infotainment or nomadic devices? ⢠Is there a difference in frequency or duration of the inter- actions across different infotainment units? ⢠How often are these interactions associated with crash or near-crash events? Is this association dependent on the duration of the interaction? ⢠Does the use of nomadic devices outside of the vehicleâs info- tainment system (e.g., iPod or MP3 player) degrade driving performance more than typical vehicle infotainment system use? If such degradation exists, is it alleviated by integration of the nomadic device with the infotainment system? ⢠To what extent does the use of vehicle-based or nomadic devices reduce drowsy driving (e.g., listening to music ver- sus listening to talk radio versus driving without listening to anything; or talking on a cell phone versus talking with a passenger versus driving without conversation)? ⢠What are the effects of learning to use new infotainment devices on driving performance? ⢠What percentage of time do drivers look at mirrors, in- vehicle or nomadic devices, signs, and external distractions? ⢠What factors (e.g., age, trying circumstances, traffic vol- ume, or controlled access versus arterial) determine the amount of distracted driving that people engage in? ⢠What types of driver distraction lead to serious consequences? ⢠How well are drivers able to divert their attention from nondriving voluntary distractions (e.g., cell phones, use of the sound system, eating, or conversing with passengers)? ⢠Does driving performance differ between drivers who are engaged in a distraction task and drivers who are attend- ing to driving? Are some safety surrogate measures more sensitive to driving performance differences when driving distracted than other safety surrogate measures? ⢠What percentage of time do drivers spend engaged in dis- tracted behavior, traveling specified speeds over the speed limit, traveling through stop-controlled or signalized inter- sections, driving in various lighting conditions, driving in rain, and driving through construction zones? ⢠What do drivers do to cause distraction and when do they do it? ⢠Do drivers reserve technology-related tasks (e.g., speaking on a cell phone or tuning a radio) for times when the driv- ing situation is relatively simple? ⢠How often and in what circumstances do drivers check speedometer and rearview mirrors? ⢠What is the relative risk of eyes off the forward roadway? ⢠Do eyes off the forward roadway significantly affect safety and/or driving performance? ⢠How do drivers adapt their level of attention and direction of gaze in response to expected and unexpected changes in driving demands? ⢠How can normative driver inattention be characterized? ⢠What is the relative risk of driving while engaging in a task that results in inattention? ⢠Is the relative risk different for different types of secondary tasks? ⢠What are the environmental conditions associated with driver choice of engagement in secondary tasks or driving while fatigued? ⢠What are the relative risks of driving inattention while encountering these environmental conditions?
69 Global Research Question 27: What Nonsafety-Related but Useful Information Can Be Obtained from These Data? These questions relate to other useful information (e.g., how often alerts occur and how drivers respond to them). This global research question represents 18 individual research questions: ⢠What spatially referenced crash and highway data exist in the regions where the driving took place, and what gaps exist in the data? ⢠Can closure data or oncoming vehicle presence (with esti- mate of speed) be obtained? ⢠Can driver interfaces be compared? ⢠Are OnStar data task dependentâe.g., phone vs. wayfinding? ⢠What useful data could be obtained from studies that track driver use and interaction with a given system? ⢠What new infotainment devices are being used in vehicles? ⢠Can new or novel uses for existing (or traditional) info- tainment devices be detected? ⢠How often do drivers activate the antilock braking system (ABS)? ⢠How often do drivers activate predictive brake assist (PBA)? ⢠How often do drivers activate electronic stability control (ESC)? ⢠How often do drivers receive forward collision warning (FCW) alerts? How often are these alerts a nuisance? ⢠How often do drivers receive lane-keeping alerts? How often are those alerts a nuisance? ⢠What are the traffic and environmental characteristics for activation of these systems and alerts? ⢠How often are different alerts presented for the same situation? ⢠What is the driver response to these multiple alerts? ⢠How effective is less-expensive methodology in answer- ing research questions? For example, does showing pho- tographs or videos of curves to drivers and asking them to estimate an appropriate speed effectively predict the speed selected by drivers in the naturalistic study? ⢠How do drivers look but not see? ⢠What are the prevalence, types, and frequency of driver inattention in which drivers engage during their daily commuting?
