Closed Test Track Research Articles

Safety Implications of Variability in Autonomous Driving Assist Alerting

Advanced Driving Assist Systems (ADAS) are on the rise in new cars, including versions that embed artificial intelligence in computer vision systems that leverage deep learning algorithms. Because these systems, at the present time, cannot operate in all operational driving domains, they employ some type of driver monitoring system for assessing driver attention, so that drivers can effectively take control if and when an ADAS system can no longer control the car. To determine the reliability of a driver alerting system when linked to autonomy that leverages deep learning, a set of increasingly complex tests were conducted on three Tesla Model 3 vehicles. Tests were conducted on a highway and a closed test track to test road departure and construction zone detection capabilities. Results revealed significant between- and within-vehicle variation on a number of metrics related to driver monitoring, alerting, and safe operation of the underlying autonomy. In some cases, cars performed better than expected but all cars exhibited both inconsistent and unsafe behaviors as well as poor driver alerting. These results highlight that a post-deployment regulatory process is ill-equipped to flag significant issues in vehicles with embedded artificial intelligence.

Field Assessment of Intersection Performance Enhanced by Traffic Signal Optimization and Vehicle Trajectory Planning

The development of Connected Automated Vehicle (CAV) technology introduces vehicle connectivity and automation into urban intersection management. It offers powerful means for accurate traffic state perception and effective traffic control actuation. This enabled the development of an intersection control algorithm that included an optimal traffic signal control algorithm and a trajectory planning function. The intersection controller aimed to maximize the intersection throughput while improving the vehicle energy efficiency via implementing adaptive signal phasing and time plans and sending reference trajectories to CAVs. Its effectiveness was tested on a closed test track equipped with a real-time traffic simulation platform, a traffic signal controller, and three physical test vehicles. The test results suggest that the intersection control algorithm was able to improve the average speed of the test vehicles by 9%, although the optimal signal controller or the trajectory planning algorithm alone could only provide marginal speed benefits. This demonstrated the advantage of combining multiple advanced traffic management functions for obtaining an elevated performance increase. For the energy efficiency analysis, both traditional gasoline-engine and hybrid vehicles were used. The hybrid test vehicles obtained fuel savings mostly via the optimal traffic signal controller (e.g., 17% fuel consumption reduction). On the other hand, the gasoline-engine test vehicle’s fuel savings could be largely attributed to the trajectory planning (e.g., 21% fuel consumption reduction). Overall, the proposed intersection controller demonstrated significant vehicle mobility and energy efficiency improvements for vehicles with different powertrains in a nearly realistic traffic condition.

Standing balance of vehicle passengers: The effect of vehicle motion, task performance on post-drive balance

BackgroundMotion platforms and driving simulators have been shown to contribute to motion sickness and a short-term increase in standing postural sway. However, no studies to date have investigated how the motion of a passenger vehicle and the performance of a task during a drive on a closed test track affects post-drive standing balance. Research QuestionsWhat are the effects of (1) a continuous, scripted drive on a closed test track, and (2) the performance of a handheld tablet-based task during the scripted drive, on post-drive standing balance? MethodsFifty adults (23 males, 27 females; 40.0 ± 20.6 yr) rode in the front passenger seat of a midsized sedan on a scripted drive. Participants were assigned to one of the acceleration levels (Low, Moderate) and completed both Task and No-Task test conditions, involving a visual-based task on a handheld tablet device. Before and after each scripted drive, participants completed two standing balance exercises: 1) feet tandem, eyes open, on firm support, and 2) feet together, eyes closed, on foam support. An inertial measurement unit (IMU) captured estimates of postural trunk sway. Root-mean-square (RMS) of angular position and velocity in the anteroposterior (A/P) and mediolateral (M/L) directions, and elliptical fit and path length of sway trajectory were computed. A nonparametric analysis was performed on the balance metrics. ResultsExposure to a scripted drive in a vehicle affected participants’ postural sway, especially after using a handheld device during the drive. M/L RMS sway velocity and path length increased for both exercises following the scripted drive with task. Additionally, M/L RMS sway increased for the more challenging balance exercise, during which participants stood with feet together on foam support with eyes closed. SignificanceThis study is the first to explore balance following a scripted drive on a closed test track. Changes in post-drive balance introduces potential risks to vehicle passengers; concurrent performance of a task on a handheld device further increases the likelihood that post-drive balance will be negatively affected.

Impact of Mixed Traffic on the Energy Savings of a Truck Platoon

<div class="section abstract"><div class="htmlview paragraph">A two-truck platoon based on a prototype cooperative adaptive cruise control (CACC) system was tested on a closed test track in a variety of realistic traffic and transient operating scenarios - conditions that truck platoons are likely to face on real highways. The fuel consumption for both trucks in the platoon was measured using the SAE J1321 gravimetric procedure as well as calibrated J1939 instantaneous fuel rate, serving as proxies to evaluate the impact of aerodynamic drag reduction under constant-speed conditions. These measurements demonstrate the effects of: the presence of a multiple-passenger-vehicle pattern ahead of and adjacent to the platoon, cut-in and cut-out manoeuvres by other vehicles, transient traffic, the use of mismatched platooned vehicles (van trailer mixed with flatbed trailer), and the platoon following another truck with adaptive cruise control (ACC). These scenarios are intended to address the possibility of “background aerodynamic platooning” impacting realized savings on public roads. Using calibrated J1939 fuel rate analysis, fuel savings for curved track sections versus straight track sections were also evaluated for these scenarios, highlighting differences in the implementation of the CACC control strategies compared to a stock ACC implementation. The use of different trailer types and the presence of passenger-vehicle traffic patterns showed a measurable impact on platoon performance in some conditions, but the basic fuel savings trends were retained.</div></div>

Comparison across vehicles of passenger head kinematics in abrupt vehicle maneuvers

Objective: Studies of vehicle occupant motions in response to abrupt vehicle maneuvers have demonstrated movements that may result in changes in the level of protection for the occupant if a crash subsequently occurs. The previous studies have typically used a single vehicle. The current study assesses whether the patterns of occupant head movement are different across passenger vehicle types.Method: Data collection was conducted on a closed test track with the same driver for all trials. A passenger sedan, a minivan, and a pickup truck were equipped with inertial measurement units to quantify vehicle dynamics. Head location was tracked using Microsoft Kinect v2 sensor and a novel methodology that fits 3 D head scan data to the depth data acquired in the vehicle. Twelve men and women with a wide range of body size and age were recruited. The primary purpose of the study was obfuscated by telling the participants that the focus was on vehicle ride motion. Participants sat in the right front seat and wore the vehicle belt. The first event during the test track route was a hard brake (approximately 1 g) to a stop from 35 mph (56 kph). Within the space of approximately 5 min the participants also experienced two aggressive, right-going lane changes, a sharp right turn with simultaneous hard braking, and a second hard braking event. The vehicles were presented in random order for each participant. This paper presents comparison across vehicles of head motions in the braking and lane-change maneuvers.Results: Accelerations were similar across the vehicles for both braking and lane-change events. The means (standard deviations) of forward head-CG excursion in the first braking event were 162 (54), 112 (39), and 176 (46) mm for the minivan, passenger car, and truck, respectively. The forward head excursion in the passenger car was found to be significantly smaller than in the other two vehicles using a paired t-test (p < 0.01). Across vehicles, the mean excursion in the second braking exposure was smaller than in the first (p < 0.01). In the first lane change event, the mean (SD) inboard head excursions were 126 (51), 110 (49), and 140 (68) mm; the values were not significantly different across vehicles or in the second lane-change event. A detailed investigation did not reveal an explanation for the smaller head excursions in the passenger car.Discussion: This is the first quantitative occupant kinematics study to compare responses across vehicles. Although a significant difference was found between vehicles, the overall responses are similar to those observed in a previous study.Conclusions: The results confirm previous studies showing large variance in excursions across occupants. Further study is needed to understand the factors that affect responses across vehicles.

Assessment of the effectiveness of a fuel additive to reduce fuel consumption of HDVs highlights the importance of verification programs

Trucks’ fuel consumption translates into large amount of greenhouse gases emissions and accounts for a large portion of the costs of transportation. This situation highlights the need for more fuel-efficient freight vehicles. In this context, several technologies have emerged to enhance heavy-duty vehicles’ (HDV’s) fuel economy. In this paper, the impact on fuel consumption due to the use of a widely used additive was tested under three test conditions using two test procedures: SAE J1321 and NCh 3331. Heavy-duty trucks and urban buses were tested on a closed test track using driving conditions similar to those found in urban operation. Another round of tests (only using trucks) was carried out on a highway. The main objective of those tests was to determine the impact of the use of the selected additive on fuel consumption under different operational conditions and to assess the merits of the additive in an emerging market. The results showed no statistical significant impacts on fuel consumption that could be attributed to the additive tested. These results highlight the need for technology verification programs that, based on rigorous testing protocols, provide policy makers in emerging countries with the technical information to determine if a fuel additive is indeed as effective as stated by the manufacturer.

On-road vehicle measurements of brake wear particle emissions

Brake wear emissions are investigated during on-road driving with a midsize passenger car on a closed test track. A novel sampling system is designed that aims at monitoring the entire aspiration of brake wear particles. The wear particles are collected by a cone-shaped sampler, which is attached at the outer side of the wheel rim. Thus, the air flow direction penetrating the brake assembly from the vehicle underbody to the vehicle outside is preserved. For analysis, the wear aerosol is routed to the trunk of the car. In addition to the emission measurements, the setup flow is monitored, which enables quantification of the acquired emission data. A 3 h subsection of the Los Angeles City Traffic (LACT) cycle, representative for realistic driving behavior, is used as test cycle. For two different brake materials, PM10 emission factors are ranging from 1.4 mg km−1 brake−1 to 2.1 mg km−1 brake−1, while one material is found to be 18% less emissive. Due to high brake disc temperatures exceeding 170 °C, high particle number emissions occur through ultrafine particle generation. The unrealistic temperatures are caused by the limited brake cooling in the semi-closed measurement setup. In contrast, the reference brake temperature does not exceed 153 °C during the same test, thus ultrafine brake particle emissions are not expected during normal driving. Furthermore, well run-in brake material shows emission factors near the lower measurement limit at the unrealistic temperatures, suggesting that ultrafine particle emissions are characteristic for brand-new materials in combination with high brake temperatures observed due to the semi-closed housing of the measurement setup.

Motion sickness in passenger vehicles during test track operations

As automation transforms drivers into passengers, the deployment of automated vehicles (AVs) has the potential to greatly increase the incidence of motion sickness. A study was conducted to quantify motion sickness response of front-seat passengers performing ecologically relevant passenger activities during conditions consistent with driving on public roadways. Fifty-two adults with a large range of self-reported levels of motion sickness susceptibility and age participated in data collection on a closed test track in a passenger sedan. Motion sickness ratings increased with task vs. no-task and moderate vs. low acceleration test conditions. Increased motion sickness susceptibility was associated with higher motion sickness ratings. In comparison to older participants (age > 60), younger participants (age < 60) experienced increased motion sickness. This is the first in-vehicle study that systematically compared normative passenger activities and acceleration magnitudes typical of normative driving conditions on motion sickness response for a large, diverse sample of passengers, enabling the exploration of the effects of covariates. Practitioner summary: The data demonstrate that a relatively large range of motion sickness response can be expected to result from passengers performing visual tasks in passenger vehicles. Measurement and modelling efforts should seek to elucidate relationships among the factors contributing to motion sickness for the purpose of informing and prioritising future countermeasures for automated vehicles (AVs). Abbreviations: AV(S): automated vehicles; BMI: body mass index; BVP: blood volume pulse; EDA: electrodermal activity; FMS: fast motion sickness scale; GPS: global positioning system; IMU: inertial measurement unit; ISO: International Organization for Standardization; MISC: misery scale; MSDV: motion sickness dose value; NDS: naturalistic driving study; SAE: Society of Automotive Engineers International; UMTRI: The University of Michigan Transportation Research Institute Key Aspect of Research: Motion sickness may be an important barrier to widespread adoption of automated vehicles @UMTRI.

Truck CACC Implementation and Test to Verify Control Performance

This paper presents quantitative driving performance results for a cooperative adaptive cruise control (CACC) system tested on Class-8 trucks. It focuses on the vehicle following control performance measured on a closed test track and in mixed traffic on public freeways. The speed and distance tracking errors are reported for the string of three trucks driven under CACC control.

Passenger head kinematics in abrupt braking and lane change events

Objective: A test track study was conducted to quantify patterns of adult front seat passenger head motion during abrupt vehicle maneuvers.Method: Eighty-seven men and women with a wide range of body sizes and ages participated in data collection on a closed test track in a passenger sedan under manual control by a test driver. Because a primary goal of the study was to gather “unaware” data, the participants were instructed that the study was concerned with vehicle dynamics and they were required to read from a questionnaire taped to the top of their thighs as the drive began. The first event was a hard brake (approximately 1 g) to a stop from 35 mph (56 kph). Within the space of approximately 5 min the participants also experienced an aggressive lane change, a sharp right turn with simultaneous hard braking, and a second hard braking event. A Microsoft Kinect v2 sensor was positioned to view the area around the front passenger seat. Head location was tracked using the Kinect data with a novel methodology that fit 3D head scan data to the depth data acquired in the vehicle.Result: The mean (standard deviation) forward excursion of the estimated head center of gravity (CG) location in the first braking event was 135 (62) mm. The forward head CG excursion in the second braking event of 115 (51) mm was significantly less than that in the first, but the difference was small relative to the within-condition variance. Head excursion on the second braking trial was less than that on the first trial for 69% of participants. The mean maximum inboard head excursion in lane-change maneuvers was 118 (40) mm. Forward head excursions in braking were significantly smaller for older passengers and those with higher body mass index, but the combined factors accounted for less than 25% of the variance. Inboard head excursion in the lane-change event was significantly related to stature, but only about 7% of variance was related to body size. Head excursions for men and women did not differ significantly after accounting for body size.Discussion: This is the first quantitative occupant dynamics study to use a large, diverse sample of passengers, enabling the exploration of the effects of covariates such as age and body size.Conclusions: The data demonstrate that a relatively large range of head positions can be expected to result from abrupt vehicle maneuvers. The data do not support simple scaling of excursions based on body size.

Using Low-cost Smartphone Sensor Data for Locating Crash Risk Spots in a Road Network

This paper investigates the use of smartphones in vehicle fleets for identifying high-risk locations in a road network, before a crash may have happened. A novel method is proposed on how to use smartphone GPS and motion sensor data to automatically recognize critical car driving situations and near-misses such as emergency braking, evasion manoeuvres or sudden driving speed changes. In the area of Vienna, Austria, approximately 200hours of driving data were collected with a dedicated smartphone app, from about 100 drivers covering more than 8,000km. Additionally, various near-miss manoeuvres were measured on a closed test track under controlled conditions. In post-processing, this data was analysed in terms of driver-specific thresholds for critical driving situations. Results show that by using this modelling approach, critical situations can be accurately identified and geographically located with smartphones. An interface to traffic management would allow near-miss information to be used along accident data in the improvement of safety and efficiency of a traffic system. A combination of the proposed method with digital maps enables future applications for traffic and fleet managers, such as a “road safety hazard map”.

Effects of License Plate Attributes on Automatic License Plate Recognition

This paper describes an experiment designed to develop a comprehensive and thorough understanding of the readability of North Carolina's license plates with an automatic license plate recognition system. This research focused on law enforcement applications and used two infrared camera systems for data collection in a controlled environment involving more than 900 license plates. The field test was conducted in a controlled environment under the following settings and conditions: a test vehicle traveling at 25 mph, nighttime evaluation, closed test track, 40 ft of spacing of license plates, 9 ft of lateral offset between the license plates and camera, standard issue and specialty plate types, standard syntax and personalized plates, and various license plate ages and conditions. The key finding of this research project is that the current, standard issue license plate with characters in blue ink has the highest capture and read rates among the plates tested in this study. Factors that decreased the capture and read rates were personalized syntax, specialty license plates, and the presence of stacked characters on a specialty license plate.

Outbound Texting

A speech-based system was evaluated to assess general task and on-road performance across vehicular control and subjective measures. The system under evaluation enabled users to send text messages and obtain route guidance through destination entry while driving. A brief introduction to the speech-based system and its capabilities was provided to participants before they were asked to complete three practice tasks. General observations of these initial uninformed interactions (i.e., absent assistance by the experimenter) with the system indicated that the system was intuitive and easy to use. Errors, when observed, were commonly related to word recognition. Participants were then instructed to navigate a closed test track at 72 km/h (45 mph) while engaging in nine secondary tasks: three manual modality texting tasks, three equivalent voice modality texting tasks, and three voice modality destination-entry tasks. As expected, driving performance measures, glance behavior, and subjective ratings were all significantly degraded during manual texting tasks as compared with similar tasks completed using voice commands. Performance during speech-based destination tasks was similar to that observed during speech-based texting. Subjectively, participants generally believed that tasks requiring the use of the speech-based interface could be accomplished safely. The majority of participants (83%) expressed a desire to have this speech-based interface available on their next vehicle.

Effects of a Computer-Based Training Module on Drivers’ Willingness to Engage in Distracting Activities

This study examines the effect of a computer-based training module on drivers' attitudes and behaviors with respect to in-vehicle distraction. Research findings on the negative performance implications of distraction call for the need to mitigate these adverse effects. Forty drivers (ages 18 to 20 yrs) were divided into two groups: a training group that completed the module and a control group that viewed an unrelated video. The training promoted enhanced metacognitive skills (e.g., planning, monitoring) and strategies to deal with distraction. Measures of willingness to perform in-vehicle activities while driving (involving the use of short videos) were assessed before and after the intervention. Drivers also performed in-vehicle tasks while driving an instrumented vehicle on a closed test track. Following the training, drivers in the training group showed a decline in their ratings of willingness to engage in distracting activities along with a corresponding increase in perceived risk. In contrast, ratings from drivers in the control group did not change on any measures. Drivers in the training group were also more likely to perform in-vehicle tasks while the vehicle was parked compared with the control group-an obvious safety benefit. However, there was no observable benefit of training for drivers who performed the distracting tasks while the vehicle was in motion. There may be some promise to such a training approach. The implications for distraction and training are discussed. Training general skills in dealing with potentially distracting in-vehicle tasks may help offset some of the negative outcomes associated with their use.

Relationship of Vertical Illuminance to Pedestrian Visibility in Crosswalks

Twenty-six participants evaluated a series of crosswalk lighting designs by visually detecting objects at each crosswalk location while traveling in a moving vehicle. The research was performed on a closed test track under nighttime conditions while the participants were driving an SUV with regular halogen headlamps. The conditions included several vertical illuminance levels (6, 10, 20, and 30 lux), varied luminaire types [high-pressure sodium (HPS) and metal halide (MH)], and various target object types (pedestrian and surrogate objects). Only one age group of participants (66 years and older) was used for the study, with equal representation of males and females. The participants were asked to detect objects at each crosswalk location when they were confident an object was present. The results indicated that object detection distances changed on the basis of vertical illuminance level, luminaire type, and object type. Object detection distance for HPS was greatest at 30 vertical lux and for MH at 20 vertical lux. However, these results were moderated by the clothing color of the target object. When object color was considered, pedestrians in white clothing were identified earlier under the HPS lighting condition at 20 lux. Under the MH configuration, denim-clothed objects were detected earlier than black-clothed objects, especially at the 20-lux lighting level. The results suggest that a vertical illuminance level of 20 lux at crosswalk locations provides adequate levels for target object detection. In addition to benefiting from vertical illuminance, target objects that wore white clothing had detection distances superior to other object types of different clothing colors. Recommendations for crosswalk lighting configurations are further discussed.

Wet Night Visibility of Pavement Markings

Fifty-three participants evaluated the visibility of four different pavement marking materials under a simulated rain system operating at 0.8 in. (20 mm) of rain per hour at night while driving a vehicle on a closed test track. The conditions tested include a variable lighting condition, glare, pavement types, and two different vehicle types. The evaluation consisted of determining the detection distance of a start or an end point of a white 4-in. edge line. Results showed that lighting improved visibility and mitigated the effects of glare. Results also showed that the wet retroreflective tape provided the longest visibility distance, followed by equivalent performance of profile thermoplastic; large glass beads with standard paint provided the shortest visibility distance. The detection distance was compared with the retroreflective performance of the pavement marking technology. It was found that a log-linear relationship exists between the retroreflectivity and the detection distance. It was also found that the level of retroreflectivity provided by the materials tested did not provide adequate visibility distance for a sedan with a 2-s visibility time at speeds greater than 45 mph.

Effects of Voice Technology on Test Track Driving Performance: Implications for Driver Distraction

This work compares the degradation in driving performance associated with secondary tasks performed with voice-based and visual/manual interfaces, including radio tuning, phone dialing, and more complex tasks involving a sequence of interactions with an in-vehicle computer system. Twenty-one participants drove an instrumented vehicle while performing a combination of car-following, peripheral target detection, and secondary tasks on a closed test track. Drivers compensated for increased task demands associated with secondary tasks by increasing their following distance. Performing secondary tasks also resulted in significant decrements to vehicle control, target detection, and car-following performance. The voice-based interface helped reduce the distracting effects of secondary task performance. Modest improvements were observed for measures of vehicle control and target detection but not for car following. The results indicated that performing in-vehicle tasks required diversion of both peripheral (visual and manual) and attentional (cognitive) resources from driving. The voice-based interface reduced the peripheral impairment but did not appreciably reduce the attentional impairment. Actual or potential applications of this research include improvements to the design of invehicle information systems and the development of evaluation protocols to assess their distraction potential.

A Demonstration of a Vision Enhancement System for State Patrol Vehicles

In conditions of poor weather and restricted visibility, it is necessary that emergency vehicles (e.g., police, ambulance, snowplows) are still able to operate and respond to critical events in the road environment. This report presents the result of a pilot study designed to evaluate a prototype Vision Enhancement System (VES) intended for use by state patrol vehicles. For this study, visibility was artificially restricted using smoked headlight covers during nighttime driving on a closed test track. The study examined the effect of preview distance and the presence of motion cues in a Head Up Display (HUD). Driving speed and self-reported data were the dependent measures related to safety and vehicle control. Despite the lack of a valid baseline, drivers reported that they felt their driving would be safer with the system than in the (imagined) case of unassisted driving in poor visibility. As a result of the apparent improvement in safety, all officers had a positive attitude toward the system.

Experimental evaluation of a co-operative driving setup based on inter-vehicle communication

This paper discusses field experiments conducted to evaluate a co-operative longitudinal controller for a cluster of vehicles with inter-vehicle communication (IVC). The controller can activelycontrol throttle, brake and gears of the used vehicles in order to realize a smooth traffic flow. For this purpose it uses two loops; the outer loop computes a desired acceleration, which the inner loop uses as a reference. The outer loop uses acceleration, velocity and position information from the own vehicle and preceding vehicles. This information is obtained by a DGPS-based Extended Kalman Filter (EKF). Real-life experiments have been performed on a closed test track. These experiments involved three vehicles of which the two rear vehicles had to anticipate automatically on the longitudinal manoeuvres of the front vehicle.

Human Factors Issues Related to Use of Vision Enhancement Systems

Vision enhancement systems (VESs) are being developed to improve nighttime driving safety by providing enhanced contrast to drivers. To determine how to evaluate the potential benefits or limitations of such systems, a small-scale investigation of driver performance and behavior with a mockup VES was conducted. To maximize external validity and minimize safety risks, a field experiment was designed and conducted on a closed test track. Four younger observers (ages 26 to 36 years) and four older observers (ages 56 to 70 years) drove an instrumented vehicle and verbally reported the detection and recognition of targets while performing speed monitoring and navigation tasks. Targets near the edges of the lane of travel were detected with and without a mock-up VES and with and without headlight glare. Video recordings of the VES, road scene, driver, and data acquisition screen were obtained. Time code, distance traveled, verbal reports, and gas pedal, brake pedal, and steering wheel measurements were recorded. Results suggested that although the mockup VES provided target contrast at longer preview distances than low-beam headlights alone, the VES enhancements were not always detected by drivers because of the visual, scanning, and cognitive demands of the driving tasks. Also, older drivers were less willing to use the mock-up VES. On the basis of verbal reports, the consensus among all observers was that the VES increased curve detection distances relative to those achieved with low-beam headlights alone. The implications of the study findings for VES use, design, and evaluation are discussed.