Crash Warning System Research Articles

Modeling the lagged impacts of hourly weather and speed variation factors on the segment crash risk of rural interstate freeways: Applying a space–time-stratified case-crossover design

In the realm of traditional roadway crash studies, cross-sectional modeling methods have been commonly employed to investigate the intricate relationship between the crash risk of roadway segments and variables including roadway geometrics, weather conditions, and speed distribution. However, these methodologies assume that the explanatory variables and target variable are only associated within the same time period. Although this assumption is well-founded for static factors like roadway geometrics, it proves inadequate when dealing with highly time-varying variables related to weather conditions and speed variation. Recent investigations have unveiled that these time-varying variables may exhibit lagged impacts on segment crash risk, necessitating the adoption of more comprehensive time-series modeling methods. This study employs two interpretable statistical methods, namely the distributed lag model (DLM) and the distributed lag nonlinear model (DLNM), to elucidate meaningful and interpretable patterns of the lagged impacts of weather and speed variation factors on segment crash risk. Empirical evidence based on crash data collected from rural interstate freeways in the state of Texas demonstrates coherent and interpretable lagged impact patterns of these variables. This study's results serve as strong support for the existence of lagged impacts on roadway segment-level crash risk, emphasizing the need for considering time-series effects in future crash modeling research. Furthermore, these findings could offer practical implications for the design of real-time crash warning systems and the effective implementation of variable speed limits to enhance road safety.

Evaluation of an Advanced Driver-Assistance System to Reduce Pedestrian and Rear-End Crashes of Transit Vehicles

This paper reports on the results of an evaluation of a rear-end and pedestrian crash warning system installed on transit agency buses with the goal of collecting and providing information to help agencies make decisions about investing in such systems. The results from this evaluation indicate that the tested crash warning system had a positive effect on improving the reaction times to rear-end and pedestrian conflicts and on increasing the yield of drivers to pedestrians. The results from the evaluation also indicate improvement in driver behavior as reflected by the increase in the time headway between vehicles, reduction in the number of alerts for both rear-end and pedestrian crashes, and the reduction in the number of hard brake events. However, bus operators’ acceptance of the system seems to be low, pointing to the need for additional outreach and education of the drivers on the system and its effectiveness. The results from the return-on-investment analysis show that although installing the system on every bus of the transit agency may not be cost-effective, installing the devices on only the buses that operate on the high-crash bus routes is cost-effective.

Development and initial testing of a time-related road safety analysis structure

The increasing availability and implementation of in-vehicle data recorder (IVDR) technologies has resulted in an increased number of safety applications based on the behavior of drivers during actual driving. The objective of this study is to formulate a flexible framework for IVDR data analysis that has the capability to include roadway geometric attributes, driver characteristics, environmental factors and time-dependencies. This research uses the concept of a homogeneous trip segment (HTS), applied with a survival model to estimate the risk of an event occurrence (e.g. crash or warning from on-board monitoring system). The University of Michigan Transportation Research Institute (UMTRI) provided data from the Road Departure Crash Warning System Field Operational Test. The survival-based model allowed the assessment of event hazard for individual drivers on specific routes as well as individual drivers compared to their peers, while controlling for travel in different routes and under different conditions. The authors believe this capability offers opportunities to safety researchers that were not available from existing methods.

NOMA-Aided Probabilistic Cooperative Transmission for PC5-Based Cellular V2X Mode 4 for Crash Warning

This paper proposes a probabilistic cooperative transmission scheme with non-orthogonal multiple access (NOMA), named NO-ProbReM, for the PC5-based cellular-vehicle-to-everything (C-V2X) mode 4 in the crash warning system (CWS). In the proposed method, each node probabilistically selects a packet based on its cooperation ability under a limited cooperation power level, which is assigned within the total transmission power limit; then, the node superposes its own packet signal and the selected packet signal on a NOMA basis. The proposed probabilistic mechanism autonomously improves the link reliability within a specific range by the limited-assigned cooperation power while guaranteeing that the direct link is sufficiently similar reliability to mode 4. Our simulation results demonstrated that with suitable parameters, the proposed method mitigated the potential channel congestion of the current mode 4; in particular, the proposed method provided 50% better performance than the current mode 4 in the fundamental node density model. These results highlight that the proposed method advanced the infrastructure-less C-V2X in the CWS.

An examination of teen drivers’ car-following behavior under naturalistic driving conditions: With and without an advanced driving assistance system

Teen drivers are overrepresented in motor vehicle crashes, and most studies concluded it was mainly due to their lack of experiences and tendencies of risk-taking. The design of advanced driving assistance systems (ADAS) aims to provide assistance in multiple stages in human information processing during driving, including environmental sensing, information processing, decision making, and vehicle controlling, in order to improve driving safety. It is expected that novice drivers may benefit more from using ADAS than adult drivers as such technologies can compensate for their frequent errors. This study examined whether and how an integrated crash warning system impacted on drivers’ following behavior, and what were the corresponding age-related differences through an analysis of two unique naturalistic driving study datasets. Significant age-related differences in car-following behavior were found. Results showed potential negative effects of ADAS on teen drivers’ following behavior that teen drivers tended to have less controlled pedal use during treatment weeks with ADAS than during baseline weeks without ADAS, while such behavior was not observed in adult drivers. All adult drivers tended to keep longer headways when driving at night than during daytime to compensate for poor vision conditions, but no such compensation behavior was observed in the teens. In addition, teen and young-adult drivers had more aggressive following behavior (with shorter mean time headway) than middle-aged and older drivers. One limitation of this study is that the findings of this study are only addressing the short-term effect of ADAS exposure, and future studies are needed to examine the longitudinal effect. The findings of this study suggest that the design of future ADAS should consider minimizing potential negative impacts on teen driver behavior.

Performance Evaluations of PC5-based Cellular-V2X Mode 4 for Feasibility Analysis of Driver Assistance Systems with Crash Warning.

This paper presents the communication performance of PC5-based Cellular-Vehicle-to-Everything mode 4 (called mode 4) to measure the feasibility of a Crash Warning System (called CWS). The CWS requires nodes (e.g., cars or pedestrians) to update its location information ten times per second. This requirement provides us with a channel congestion problem. To investigate feasibility in terms of channel congestion, we evaluated communication performance in various crash scenarios by computer simulation. One of the serious scenarios is a crowded environment like large intersections. In the uniform node distribution, in which we evaluated average performance, mode 4 accommodated 26% fewer nodes than the expected one; in a realistic node distribution, mode 4 achieved 55% worse performance than the CWS requirements. Our results highlighted the need for performance improvements of mode 4 for CWS in practical uses.

Developing a Crash Warning System for the Bike Lane Area at Intersections with Connected Vehicle Technology

A common type of bike lane at intersections is between the through lane and the right lane. With such design, right-turning drivers need to cross the bike lane to merge into the right lane, which could cause conflicts with bicycles on the keyhole bike lane. This study aims to develop a warning system for drivers to avoid vehicle–bicycle crashes in the bike lane area under a connected vehicle environment. To propose a reasonable warning system, 118 right-turning vehicle trajectories were collected by an unmanned aerial vehicle. Drivers’ right-turning behaviors are investigated based on the trajectory data. Then, a vehicle–bicycle crash warning algorithm is proposed to calculate the post-encroachment time (PET) under different situations. By comparing the threshold value and the PET value, potential vehicle–bicycle crash locations in the bike lane area could be identified. The proposed algorithm is designed to be displayed on front windshields with an augmented reality display. The results suggested that the proposed algorithm could provide high prediction accuracy. Moreover, vehicle speed, vehicle location, bicycle speed, and bicycle location were found to have significant impact on the locations of dangerous areas. It is expected that the proposed warning system could be used to identify the dangerous areas and deliver warning information for right-turning drivers when they are approaching an intersection. The warning system could help drivers be more prepared for the upcoming right-turning maneuver, and thus improve traffic safety for both drivers and cyclists at intersections.

Effects of crash warning systems on rear-end crash avoidance behavior under fog conditions

Reduced visibility conditions increase both the probability of rear-end crash occurrences and their severity. Crash warning systems that employ data from connected vehicles have potential to improve vehicle safety by assisting drivers to be aware of the imminent situations ahead in advance and then taking timely crash avoidance action(s). This study provides a driving simulator study to evaluate the effectiveness of the Head-up Display warning system and the audio warning system on drivers’ crash avoidance performance when the leading vehicle makes an emergency stop under fog conditions. Drivers’ throttle release time, brake transition time, perception response time, brake reaction time, minimum modified time-to-collision, and maximum brake pedal pressure are assessed for the analysis. According to the results, the crash warning system can help decrease drivers’ reaction time and reduce the probability of rear-end crashes. In addition, the effects of fog level and drivers’ characteristics including gender and age are also investigated in this study. The findings of this study are helpful to car manufacturers in designing rear-end crash warning systems that enhance the effectiveness of the system’s application under fog conditions.

Collision Avoidance Via Emergency Steering Warning System: A Driving Simulator Approach

This study analyzes the viability of an Emergency Steering Warning System (ESWS) to improve the safety of vehicles on highways traveling in the same direction. The proposed system evaluates the vehicle’s physical limits, driver’s reaction and assists in making the most logical decision to avoid a crash using a sound or a similar stimulus. Typical driving simulator events were designed in MATLAB/Simulink and IPG/CarMaker co-simulation environment. In the predetermined scenario, the leading vehicles suddenly move into the host vehicle’s lane and the driver is expected to avoid crash by either steering or braking. The ESWS system generates a sound stimulus when it is determined that the crash is unavoidable with the use of service brakes and the only way to avoid the obstacle is steering. The simulation events were performed by a group of participants using a driver simulator with and without the ESWS system. The proposed ESWS encouraged participants to do an earlier and smoother steering maneuver which can be advantageous in some certain critical traffic situations. The statistical results showed that the sound stimulus reduced the drivers’ reaction time significantly and a number of accidents can be avoided by the suggested crash warning system.

An on-road evaluation of connected motorcycle crash warning interface with different motorcycle types

Crash warning systems have been deployed in the high-end vehicle market segment for some time and are trickling down to additional motor vehicle industry segments each year. The motorcycle segment, however, has no deployed crash warning system to date. With the active development of next generation crash warning systems based on connected vehicle technologies, this study explored possible interface designs for motorcycle crash warning systems and evaluated their rider acceptance and effectiveness in a connected vehicle context. Four prototype warning interface displays covering three warning mode alternatives (auditory, visual, and haptic) were designed and developed for motorcycles. They were tested on-road with three connected vehicle safety applications - intersection movement assist, forward collision warning, and lane departure warning - which were selected according to the most impactful crash types identified for motorcycles. Combined auditory and haptic displays showed considerable promise for implementation. Auditory display is easily implemented given the adoption rate of in-helmet auditory systems. Its weakness of presenting directional information in this study may be remedied by using simple speech or with the help of haptic design, which performed well at providing such information and was also found to be attractive to riders. The findings revealed both opportunities and challenges of visual displays for motorcycle crash warning systems. More importantly, differences among riders of three major motorcycle types (cruiser, sport, and touring) in terms of rider acceptance of a motorcycle crash warning system were revealed. Based on the results, recommendations were provided for an appropriate crash warning interface design for motorcycles and riders in a connected vehicle environment.

Develop right‐turn real‐time crash warning system at arterial access considering driver behaviour

To help drivers safely enter the arterial road from the access road, the authors develop a crash warning system for vehicles in right-turn scenario based on DSRC (dedicated short range communications). Drivers’ right-turn behaviours from an access road to an arterial highway are considered in the system. Warning algorithms were tested with field data and DSRC on-board and roadside equipment. Corresponding outliers filter shows a reliable performance. In this system, right-turn process is divided into three phases: turn-in, keep-steady, and turn-out. Based on the field data, they establish regression models for each phase. Model results show that: (i) the overall duration of the three phases of the right-turn manoeuvre increases with the amount of cars coming from left on main artery; (ii) the amount of cars that are influenced by the arterial traffic increases the duration of first two phases, but decreases the last phase duration; (iii) the longer the first two phases last, the shorter the last phase would be; and (iv) drivers tend to decelerate before turning right when there are more than two cars coming from left.

Longitudinal Driving Behavior with Integrated Crash-Warning System

This study created the most extensive set of naturalistic data that has ever been gathered on the following behavior of drivers when interacting with a forward crash-warning system. For the purposes of this paper, data from the naturalistic driving study of the Integrated Vehicle-Based Safety System (IVBSS) program were used. IVBSS data collected from a total of 108 drivers, representing 81,163 steady state following events and 20,096 forward conflict events were extracted and compared. Drivers were from three age groups (younger, middle-aged, and older) and balanced between two gender groups. Three objective measures were used in this study: mean time headway, minimum time to collision, and proportion of time drivers spent in time headway of 1 s or less. Drivers used the research vehicles for 40 days, with the system not activated for the first 12 days and activated for the following 28 days. A linear mixed model was used for the data analysis. Results of this study show that drivers have a tendency to follow more closely when the warning system is activated. It is recommended that a visual display for feedback on real-time safe following distance may help drivers keep a safer distance. This study also observed age-related self-regulation behavior when other vehicles were being followed and showed that older drivers tended to follow farther away from the leading vehicle.

Heavy-Truck Drivers’ Following Behavior With Intervention of an Integrated, In-Vehicle Crash Warning System

This study is designed to evaluate heavy-truck drivers' following behavior and how a crash warning system influences their headway maintenance. Rear-end crashes are one of the major crash types involving heavy trucks and are more likely than other crash types to result in fatalities. Previous studies have observed positive effects of in-vehicle crash warning systems in passenger car drivers. Although heavy-truck drivers are generally more experienced, driver-related errors are still the leading factors contributing to heavy-truck-related rear-end crashes. Data from a 10-month naturalistic driving study were used. Participants were 18 professional heavy-truck drivers who received warnings during the last 8 months of the study (treatment period) but not during the first 2 months (baseline period). Time headway and driver's brake reaction time were extracted and compared with condition variables, including one between-subjects variable (driver shift) and five within-subjects variables (treatment condition, roadway types, traffic density, wiper state, and trailer configuration). The presence of warnings resulted in a 0.28-s increase of mean time headway with dense on-road traffic and a 0.20-s increase with wipers on. Drivers also responded to the forward conflicts significantly faster (by 0.26 s, a 15% enhancement) in the treatment condition compared with responses in the baseline condition. Positive effects on heavy-truck drivers' following performance were observed with the warning system. The installation of such in-vehicle crash warning systems can help heavy-truck drivers keep longer headway distances in challenging situations and respond quicker to potential traffic conflicts, therefore possibly increasing heavy-truck longitudinal driving safety.

Design and Validation of Safety Cruise Control System for Automobiles

In light of the recent humongous growth of the human population worldwide, there has also been a voluminous and uncontrolled growth of vehicles, which has consequently increased the number of road accidents to a large extent. In lieu of a solution to the above mentioned issue, our system is an attempt to mitigate the same using synchronous programming language. The aim is to develop a safety crash warning system that will address the rear end crashes and also take over the controlling of the vehicle when the threat is at a very high level. Adapting according to the environmental conditions is also a prominent feature of the system. Safety System provides warnings to drivers to assist in avoiding rear-end crashes with other vehicles. Initially the system provides a low level alarm and as the severity of the threat increases the level of warnings or alerts also rises. At the highest level of threat, the system enters in a Cruise Control Mode, wherein the system controls the speed of the vehicle by controlling the engine throttle and if permitted, the brake system of the vehicle. We focus on this crash area as it has a very high percentage of the crash-related fatalities. To prove the feasibility, robustness and reliability of the system, we have also proved some of the properties of the system using temporal logic along with a reference implementation in ESTEREL. To bolster the same, we have formally verified various properties of the system along with their proofs.

DESIGN AND VALIDATION OF SAFETY CRUISE CONTROL SYSTEM FOR AUTOMOBILES

In light of the recent humongous growth of the human population worldwide, there has also been a voluminous and uncontrolled growth of vehicles, which has consequently increased the number of road accidents to a large extent. In lieu of a solution to the above mentioned issue, our system is an attempt to mitigate the same using synchronous programming language. The aim is to develop a safety crash warning system that will address the rear end crashes and also take over the controlling of the vehicle when the threat is at a very high level. Adapting according to the environmental conditions is also a prominent feature of the system. Safety System provides warnings to drivers to assist in avoiding rear-end crashes with other vehicles. Initially the system provides a low level alarm and as the severity of the threat increases the level of warnings or alerts also rises. At the highest level of threat, the system enters in a Cruise Control Mode, wherein the system controls the speed of the vehicle by controlling the engine throttle and if permitted, the brake system of the vehicle. We focus on this crash area as it has a very high percentage of the crash-related fatalities. To prove the feasibility, robustness and reliability of the system, we have also proved some of the properties of the system using temporal logic along with a reference implementation in ESTEREL. To bolster the same, we have formally verified various properties of the system along with their proofs.

Investigation Into the Effect of an Intersection Crash Warning System on Driving Performance in a Simulator

Objective: The objective of this research was to examine the effects on driving performance of a prototype intersection collision warning system (ICWS) that is based on the dedicated short-range communication (DSRC) technology concept. Methods: An experimental study with 32 participants using a driving simulator was conducted to examine the effects of ICWS on the driving performance of different drivers sorted by gender (male, female) and experience (experienced, novice) compared across 3 warning conditions: no warning, audio warning, and visual warning. Each participant completed 3 test, drives with each drive comprising 3 events. Each event contained a combination of scenario type (cross-traffic from left/right scenario, right turn against scenario) and warning condition. Results: The results showed that an ICWS, in general, could reduce the number of intersection crashes by approximately 40 to 50 percent and shorten drivers’ reaction times to brake in response to emergent events occurring at intersections. Moreover, drivers’ reaction times to brake in response to the audio warning system were significantly shorter than in response to the visual warning system in the cross-traffic from right scenario. In addition, speeds were reduced in all 3 scenarios and deceleration rates increased in the cross-traffic from left and right turn against scenario under the influence of ICWS. Conclusions: In general, the results provide overall support for ICWSs based on the DSRC technology concept. The broader implications of the research are discussed.

Real-World Frequency of Use of Automotive Lighting Equipment

This study provides information about average annual use of the following automotive lighting equipment by U.S. drivers: low- and high-beam headlamps, turn signals, and stop, back-up, parking, sidemarker, and tail lamps. The data were collected as part of a naturalistic field study of crash warning systems. Eighty-seven randomly selected drivers from southeastern Michigan were provided with instrumented research vehicles (11 identical 2003 Nissan Altimas) for periods averaging 26 days and instructed to drive the vehicles as their personal vehicles.The results are presented for each lamp type in terms of the average annual hours of use and minutes used per 100 km driven. These findings are discussed in relation to the rated life of various lamps and the average life of vehicles in the U.S.License plate, parking, sidemarker, and tail lamps were the most frequently used automotive lighting equipment, averaging just over 100 hours per year. The least used lamps were back-up lamps, which were used less than five hours per year. Average annual hours of lamp use decreased with increasing driver age. While rates of use for stop, turn signal, and back-up lamps were similar for females and males, male drivers accrued 34 percent more hours of nighttime driving than female drivers, while using their high beams about half as often.

Method for Identifying Vehicle Movements for Analysis of Field Operational Test Data

The independent evaluation of a roadway-departure crash-warning system will involve identifying and classifying conflicts and near-collisions from a vast quantity of field data. The classification of these events includes identifying vehicle movements such as negotiating a curve, making a turn, changing lanes, and merging. A unified algorithm that relies solely on vehicle kinematic data is developed for identifying such movements. The method works reliably for various types of road surfaces, road types, speeds, and conditions. The algorithm relies on metrics such as heading angle, lateral position, radius of curvature, and peak yaw rate—calculated from yaw rate and vehicle speed data—to classify vehicle-movement events from a large file of vehicle data. Tuning parameters for the algorithm, set both analytically and empirically, are provided. The results of the tests show that the algorithm makes correct identifications of vehicle movement about 80% of the time. The highest success is for turns, followed by curves and lane changes. Although these numbers improve on previous methods, there is additional room for improvement that gives impetus for future work.

Injury Severity in Multivehicle Rear-End Crashes

Rear-end crashes constitute a substantial portion of the total crashes in the United States. They are also amenable to reduction through emerging intelligent transportation systems technologies such as crash warning systems. A specific objective was to analyze the effect of information and vehicle technology on injury severity in rear-end crashes, while controlling for the effects of driver, vehicle, and roadway factors. The study is based on real-life data from the Highway Safety Information System for North Carolina access-controlled roadways. The results show that in two-vehicle crashes the leading driver is more severely injured, whereas in three-vehicle crashes the driver in the middle is more severely injured. To analyze injury severity on the KABCO scale, three separate ordered probit models were estimated for Drivers 1 (leading), 2 (striking), and 3 (striking, in a three-vehicle crash). A vehicle age variable was used in the model specification to capture the effect of vehicle age and to serve as a proxy for safety improvements, in particular the center high-mounted stoplight (CHMSL). The modeling results show that being in a newer vehicle protects the driver in rear-end collisions. Similarly, being in a newer vehicle protects Driver 2. Interestingly, striking a newer Vehicle 1 can reduce the chance of both Driver 2 and Driver 3 injuries, partly as a result of CHMSL on Vehicle 1. Also examined is whether drivers of vans, pickup trucks, and station wagon cars/trucks sustain less-severe injuries because of their larger vehicle mass or more-severe injuries because of their information-blocking effect. The results show that technological improvements have a quantifiable beneficial effect on safety.

Rear-End Collision–Warning System: Design and Evaluation via Simulation

The design of an innovative rear-end collision-warning system was evaluated for effectiveness. The crash scenario involves a lead vehicle not moving (LVNM) in one lane of a straight, dry, paved arterial road and a following vehicle approaching in the same lane. The LVNM has a rearfacing sensor and is equipped with the rear crash-warning system, which allows the LVNM to flash its brake lights or its center high-mounted stop lamp, warning the following vehicle that it is approaching too rapidly. Because this problem is complex, the scope was narrowed, and it was assumed that the driver of the following vehicle always detected the warning after a response time lag and then applied hard braking. The warning algorithm (i.e., selecting the most appropriate warning distance for each approaching vehicle speed) was designed based on trade-offs to maximize the capability of preventing crashes, reduce the frequency of nuisance alarms, and minimize the severity of crashes. The overall measures of effectiveness of the warning design were then evaluated for a vehicle speed distribution that represented a suburban arterial road. The findings suggest that the warning system should be very effective in preventing crashes. The expected number of nuisance alarms was small, and for the very small percentage of vehicles that would crash, the expected crash severity was negligible. Experimental studies and field operational tests would be required to obtain more accurate numerical values for the design parameters.