Dawn Marshall

Alerts for In-Vehicle Information Systems: Annoyance, Urgency, and Appropriateness

Objective: This study assesses the influence of the auditory characteristics of alerts on perceived urgency and annoyance and whether these perceptions depend on the context in which the alert is received. Background: Alert parameters systematically affect perceived urgency, and mapping the urgency of a situation to the perceived urgency of an alert is a useful design consideration. Annoyance associated with environmental noise has been thoroughly studied, but little research has addressed whether alert parameters differentially affect annoyance and urgency. Method: Three 23 × 3 mixed within/between factorial experiments, with a total of 72 participants, investigated nine alert parameters in three driving contexts. These parameters were formant (similar to harmonic series), pulse duration, interpulse interval, alert onset and offset, burst duty cycle, alert duty cycle, interburst period, and sound type. Imagined collision warning, navigation alert, and E-mail notification scenarios defined the driving context. Results: All parameters influenced both perceived urgency and annoyance (p < .05), with pulse duration, interpulse interval, alert duty cycle, and sound type influencing urgency substantially more than annoyance. There was strong relationship between perceived urgency and rated appropriateness for high-urgency driving scenarios and a strong relationship between annoyance and rated appropriateness for low-urgency driving scenarios. Conclusion: Sound parameters differentially affect annoyance and urgency. Also, urgency and annoyance differentially affect perceived appropriateness of warnings. Application: Annoyance may merit as much attention as urgency in the design of auditory warnings, particularly in systems that alert drivers to relatively low-urgency situations.

Effects of Adaptive Cruise Control and Alert Modality on Driver Performance

This article reports on a study that assessed the ability of automobile drivers to make the transition from adaptive cruise control (ACC) to manual control when warned with alerts of different modalities. The authors compared how drivers maintain headway distance in conditions with and without ACC in mild, moderate, and severe braking situations. The different modalities tested include visual, auditory, seat vibration, brake pulse, and a combination of these methods. The two scenarios studied were a braking lead vehicle and an abrupt lane change of a lead vehicle that reveals a slow-moving vehicle. The study included sixty people aged 30 to 50 years, split evenly by gender and used to using cruise control (defined as at least twice per month). After a demographic questionnaire and pre-drive instruction, participants drove a 6-minute practice drive, followed by a 35-minute experimental drive. The results showed that ACC helped drivers maintain a larger safety margin, as measured by the minimum time-to-collision (TTC). The authors hypothesize that this larger safety margin may have important indirect benefits, affecting other drivers and the overall traffic flow rather than the likelihood of a crash for the driver using the ACC. The various alert modalities performed similarly when considered independently. There was a slightly greater minimum TTC associated with the brake pulse in moderately severe situations. Readers are referred to the full report at www.ntis.gov (access number PB2009-102474). Keywords: Driver distraction;

Enhancing interaction with the driving ecology through haptic interfaces

Technology developments in the areas of sensors, controllers, wireless communication, and low-cost computers dramatically change driving. Concerns about distraction due to a wide array of in-vehicle information systems (e.g., voice-based email systems) coupled with an increasing degree of automatic vehicle control systems (e.g., adaptive cruise control) present important design challenges. This technology may distance drivers from the driving situation and may delay their responses to unanticipated, high-demand situations. One way to address this issue is to provide the driver with additional information and warnings; however, additional auditory information may be annoying and visual displays may be distracting. Haptic interfaces offer a promising alternative. This paper describes how techniques adapted from ecological interface design might help identify how different types of haptic interfaces might best convey driving-related information

Drivers’ Behavior Through a Yellow Light Effects of Distraction and Age

The decision to proceed through an intersection once the traffic signal has changed to yellow may increase the risk for a collision. This study sought to understand how age differences, cell phone use, and time to the stop line affected the likelihood that a driver would continue through a yellow light as observed in a driving simulator study. Four age groups were examined; novice (16 years), younger (18-25 years), middle (30-45 years) and older (50-60 years). The novice drivers were also between four to eight weeks of licensure. The likelihood that a driver would either drive through a yellow phase or stop was examined using a logistic regression model. A significant interaction effect between age groups and cell phone use was observed. More specifically, novice drivers talking on a handheld phone were significantly more likely than middle-aged drivers to proceed through the intersection. This study examines the safety consequences that may result for these novice drivers as they engage in distracting tasks.

Annoyance and Urgency of Auditory Alerts for in-Vehicle Information Systems

The proliferation of in-vehicle information systems and the need for drivers to keep their eyes on the road suggest that auditory alerts will become increasingly common. This study examined how sound parameters affected perceived urgency and annoyance. The sound parameters investigated were overall density of a warning tone, pulse speed and type of burst used to create a warning tone. The context in which the auditory alert is presented was an additional factor. Significant effects were found for all factors. Annoyance and urgency of an alert depend on the context in which it is presented and sound parameters interact with context to affect the perceived urgency of alerts. Like urgency, annoyance displayed systematic variation as a function of warning signal parameters. These results suggest that auditory alert design should go beyond mapping perceived urgency of the alert to the urgency of messages, but should also consider a tradeoff analysis that addresses the costs of increasing annoyance.

Cost of Warning of Unseen Threats

One goal of the connected vehicle program is to raise the situation awareness of drivers to unseen events in the driving environment. Warnings of unseen threats may prompt a directed visual search for that threat at the expense of overlooking other intervening threats along the way. This study assessed the distraction potential of alerts to unseen threats. Twenty-two participants drove an instrumented vehicle on a closed course and encountered threat situations, such as a car entering the road from a side road obstructed from the drivers view. On each pass, there were two sandbags that served as secondary threats, and the driver was instructed to press a response button whenever one was detected. The control condition bags were placed at locations on the course where the driver was undistracted and encountered no primary threats. The threat bags were positioned so that they became visible shortly after the warning of a primary threat appeared on an in-vehicle display but before the primary threat became visible. The results showed that advance warnings improved primary threat detection time. That is, when drivers were given advance warning of the presence of an upcoming threat, the drivers identified the presence of the threat sooner than when no warning was given. Unfortunately, this facilitation came at a cost of reduced detection distance and reaction time to the secondary threats that were present in the roadway. Future research should investigate whether this effect persists for more critical secondary threats.

Factors Affecting Drivers’ Ability to Detect Motorcycles During Daylight in a Simulated Environment

This paper investigates the effect of headlight type (daytime running lights, high beams, and modulating headlights) and rider color (bright yellow, blue denim, and black clothing and helmet) on the visual conspicuity of a motorcycle to younger (25 to 55 years old) and older drivers (65 and older) of a passenger vehicle in simulated urban and rural environments. Thirty-six participants completed two study drives on the National Advanced Driving Simulator-2. During the drives, participants were presented with six oncoming motorcycles and three leading parked motorcycles, each with a different combination of rider color and headlight type. Participants indicated when each motorcycle was first visible to them by pressing a button on the steering wheel of the driving simulator for different combinations of rider colors and headlight types. Detection distances from the motorcycles to the participant vehicles were recorded and analyzed. Repeated measures of analysis of variance indicated significant main effects of headlight types as well as interaction effects between rider color and headlight type for oncoming motorcycles. Results also revealed significant main effects of driving environments and rider color, and interaction effects among the driving environments, rider color, and age groups of the participants for leading motorcycles. The results revealed the importance of using a modulating headlight and wearing a bright helmet and clothing while riding motorcycles to increase motorcycle conspicuity. These findings can be put into practice in the design of motorcycle conspicuity-related campaigns and interventions, such as encouraging riders to use modulating headlights and to wear appropriate clothing.

Use of High-Fidelity Simulation to Evaluate Driver Performance with Vehicle Automation Systems

Automation is an important tool for improving driver safety over the coming decades. Vehicle automation will tend to be implemented in stages with the intent of incrementally increasing the overall safety of driving through the reduction in crashes related to driver error. Driving simulators play a critical role in assessing the effectiveness of these new technologies. This paper discusses vehicle automation and provides several examples of the use of high fidelity simulators to evaluate new automation technologies in several different forms.

How Does Lane Departure Warning Effectiveness Vary by Severity of Departure

Lane departures are a significant traffic safety problem. They can be attributed to a variety of types of impairment including the increasing prevalence of distracted driving. Research to date has focused on how drivers respond to imminent lane departure warnings, often with short time to line crossing at the onset of the alert. This paper examines how this effectiveness changes over a range of severities associated with various times to line crossing. Although warning systems are generally beneficial in reducing the severity of lane departures, time to line crossing had mixed effects on lane departures. Longer time to line crossing was associated with a greater likelihood of departing the lane but with less severe lane departures. Additionally, an active warning that provides steering torque to help correct lane departures showed decreased effectiveness with increasing time to line crossing in terms of likelihood of lane departure and duration and area of lane departure. These results point to the importance of considering the range of situations in which a warning may be issued, not just the most severe cases.

Drivers’ Avoidance Strategies When Using a Forward Collision Warning (FCW) System

Forward collision warning (FCW) systems help prevent rear-end collisions by identifying and alerting drivers of threats ahead. Understanding drivers’ avoidance strategies i.e. the tendency to brake or steer is important for the design and effectiveness of these systems. A driving simulator study was performed across five US locations to examine three driver avoidance maneuvers: braking only, steering only and combined braking and steering. A log-linear analysis was used to investigate the likelihood of an avoidance maneuver given the driver characteristics (age, gender) and study location. Findings showed that drivers aged 40 years and older were more likely to use a combined braking and steering maneuver to avoid a rearend collision. Drivers from two coastal urban areas (Washington, D.C. and Seattle, WA) were less likely to choose braking only in response to FCW alerts. Younger drivers and drivers that live in more rural areas (Clemson, SC and Iowa City, IA) were more likely to select braking only to avoid a crash, which could be due to their experience in less congested traffic environment. The findings of this study provide some insights on the factors associated with various avoidance strategies among drivers. This understanding can help guide the design of future in-vehicle collision warning systems.