Crash risk of ESC-fitted passenger cars

Objective: We examined both fatal and injury at-fault crashes of a population of passenger cars fitted with electronic stability control (ESC). Crash rates were calculated in relation to both registration years and mileage. Crash rates were also calculated for a non-ESC car population and crash rate ratios were calculated to compare the crash risk between ESC-fitted and non-ESC-fitted passenger cars.

Methods: Passenger car models with and without ESC were identified (ESC-equipped cars: 3,352,813 registration years; non-ESC-equipped: 5,839,946 registration years) and their vehicle information for the period 2009–2013, including mileage (ESC-equipped vehicles: 89.3 billion kilometers; non-ESC-equipped: 72.4 billion kilometers), was drawn from the national Vehicular and Driver Data Register.

The registry of Finnish road accident investigation teams was accessed and all fatal at-fault crashes among the cars in the study populations (ESC 97; non-ESC 377) for the period 2009–2013 were analyzed. The motor insurance database includes at-fault crashes leading to injuries and was utilized for analyses (ESC: N?=?8,827, non-ESC: N?=?21,437).

Crash rates and crash rate ratios were calculated to evaluate crash risk of both ESC-equipped and non-ESC-equipped passenger cars. Poisson regression was used to model crash involvement rate ratios both per registration year and per mileage for vehicles with ESC and without ESC, controlling for age and gender of the vehicle owner and vehicle mass.

Results: Passenger cars fitted with ESC showed lower crash rates than non-ESC-equipped cars in all crash types studied. In general, the difference in crash rates between ESC-equipped and non-ESC-equipped vehicles was greater when the crashes were compared to the mileage rather than registration years. The mileage-proportional crash rate of ESC-equipped cars was 64% (95% confidence interval, 61%; 67%) lower in run-off-road crashes resulting in injury and as much as 82% (65%; 91%) lower in fatal run-off-road crashes when suicides and disease attacks were not taken into account.

Conclusions: Our results show that modern passenger cars provide a significant crash risk reduction, which depends on both ESC and passive safety features introduced. Results also show that exposure evaluation in terms of registration years (or vehicle population) instead of true mileage can provide an overly pessimistic view of the crash risk.     

Side impact crashes--factors affecting incidence and severity: review of the literature

Many traffic crashes are side impact collisions resulting in significant death and injury. A review was conducted of the evidence of driver, road, and vehicle characteristics affecting either the risk of occurrence or the severity of injury in such crashes for papers published from 1996 to early 2003. For drivers, evidence was found of increased crash risk or injury severity only for age and age-related medical conditions (e.g., dementia). Traffic roundabouts and other traffic control devices--stop signs, traffic lights, and so on--had mixed results; traffic controls were better than no controls, but their effectiveness varied with circumstance. Most vehicle characteristics have had little or no effect on crash occurrence. Antilock braking systems (ABS) in the striking vehicle had been anticipated to reduce the risk of crashes, but so far have demonstrated little effect. The primary emphasis in vehicle design has been on protective devices to reduce the severity of injury. Disparity in the size of the two vehicles, especially when the struck vehicle is smaller and lighter, is almost a consistent risk factor for occupant injury. The occupants of light trucks, however, when struck by passengers cars on the opposite side, were at higher risk of injury. Wearing seat belts had a consistently protective effect; airbags did not, but there were few studies, and no field studies, of lateral airbags found. Of all the characteristics examined, vehicle design, including occupant restraints, is the most easily modified in the short term, although road design, traffic control, and the monitoring of older drivers may also prove effective in reducing side impact crashes in the longer term.     

Effects of electronic stability control: an update

OBJECTIVE: An earlier study reported that electronic stability control (ESC) in passenger vehicles reduced single-vehicle crash involvement risk by 41% and single-vehicle fatal crash involvement risk by 56%. The purpose of the present study was to update these effectiveness estimates using an additional year of crash data and a larger set of vehicle models. METHODS: The amount of data increased by half, allowing for separate effectiveness estimates for cars and sport utility vehicles (SUVs) and a more detailed examination of multiple-vehicle crash types. Crash involvement rates per registered vehicle were compared for otherwise identical vehicle models with and without ESC. RESULTS: Based on all police-reported crashes in 10 states during three years, ESC reduced single-vehicle crash involvement risk by approximately 41%. Effects were significantly higher for SUVs than for cars. ESC reduced single-vehicle crash involvement risk by 49% for SUVs and 33% for cars. Based on all fatal crashes in the United States during four years, ESC was found to have reduced single-vehicle fatal crash involvement risk by 56%. Again, effectiveness estimates were higher for SUVs than for cars--59% for SUVs and 53% for cars, but these differences were not statistically significant. Multiple-vehicle fatal crash involvement risk was reduced by 32%-37% for SUVs and 25% for cars. CONCLUSIONS: The present study confirms the results of the earlier study. There are significant reductions in single-vehicle crash rates when passenger vehicles are equipped with ESC. In addition, ESC leads to reductions in severe multiple-vehicle crashes.     

Trends in aggressivity and driver risk for cars,SUVs, and pickups: Vehicle incompatibility from 1989 to 2016

Abstract

Objective: When 2 vehicles of different sizes collide, the occupants of the smaller vehicle are more likely to be injured than the occupants of the larger vehicle. The larger vehicle is both more protective of its own occupants and more aggressive toward occupants of the other vehicle. However, larger, heavier vehicles tend to be designed in ways that amplify their incompatibility with smaller, lighter vehicles (by having a higher ride height, for example). A 2012 study by the Insurance Institute for Highway Safety (IIHS) concluded that fatalities caused by design incompatibility have decreased in recent years. The current study was conducted to update the 2012 IIHS analysis and to explore trends in vehicle incompatibility over time.

Methods: Analyses examined deaths in crashes involving 1- to 4-year-old passenger vehicles from 1989 to 2016 collected from the Fatality Analysis Reporting System (FARS). Trends in driver risk were examined by comparing driver death rates per million registered vehicle years across vehicle type and size. Trends in aggressivity were examined by comparing partner driver death rates across vehicle type and size.

Results: Cars and SUVs have continued their trend toward reduced incompatibility. In 1989–1992, SUVs were 132% more likely to kill the driver in a partner car compared with when a car crashed with another car. By 2013–2016, this value had dropped to 28%. Pickups and cars remain just as incompatible in 2013–2016 as they were in 1989–1992, however (159% vs. 158%). Remaining pickup incompatibility may be largely due to excess curb weight rather than to shape or design features, because light pickups were just 23% more likely to kill the driver in a partner car compared with when a car crashed with another car.

Conclusions: The trend toward reduced fleet incompatibility has continued in the latest crash data, particularly for cars and SUVs. Although pickup–car incompatibility has also decreased over time, pickups remain disproportionately aggressive toward other vehicles, possibly due to their greater average curb weight. Reducing the weight of some of the heaviest vehicles and making crash avoidance technology fitment more widespread may be promising means to reduce remaining fleet incompatibility. Identifying the source of remaining incompatibility will be important for safety improvements going forward.     

Rage against the machine? Google's self-driving cars versus human drivers

IntroductionAutomated driving represents both challenges and opportunities in highway safety. Google has been developing self-driving cars and testing them under employee supervision on public roads since 2009. These vehicles have been involved in several crashes, and it is of interest how this testing program compares to human drivers in terms of safety.MethodsGoogle car crashes were coded by type and severity based on narratives released by Google. Crash rates per million vehicle miles traveled (VMT) were computed for crashes deemed severe enough to be reportable to police. These were compared with police-reported crash rates for human drivers. Crash types also were compared.ResultsGoogle cars had a much lower rate of police-reportable crashes per million VMT than human drivers in Mountain View, Calif., during 2009–2015 (2.19 vs 6.06), but the difference was not statistically significant. The most common type of collision involving Google cars was when they got rear-ended by another (human-driven) vehicle. Google cars shared responsibility for only one crash.ConclusionsThese results suggest Google self-driving cars, while a test program, are safer than conventional human-driven passenger vehicles; however, currently there is insufficient information to fully examine the extent to which disengagements affected these results.Practical applicationResults suggest that highly-automated vehicles can perform more safely than human drivers in certain conditions, but will continue to be involved in crashes with conventionally-driven vehicles.     

Effect of vehicle and crash factors on older occupants

PROBLEM: The expected substantial increase in people aged 65 or older is important for those concerned about transportation injuries. However, much of the previous research concentrates on older drivers and overlooks the fact that vehicle and crash factors may provide significant explanations of older occupant injury rates. METHOD: Differences across age groups are explored using two nationwide travel surveys, crash involvement, fatalities, and injuries from crash databases and an ordered probit model of injury severity. RESULTS AND DISCUSSION: Two noticeable differences that help explain injury risk are that older people are more likely to travel in passenger cars than younger people who frequently use light trucks, and that seriously injured older occupants are more likely to be involved in side-impact crashes than their younger counterparts. IMPACT: Increased attention to vehicle engagement in side-impact crashes and to vehicle technologies that can help drivers avoid side collisions would be particularly helpful for older occupants.     

An examination of the increases in pedestrian motor-vehicle crash fatalities during 2009–2016

IntroductionPedestrian fatalities increased 46% in the United States during 2009–2016. This study identified circumstances under which the largest increases in deaths occurred during this period.MethodAnnual counts of U.S. pedestrian fatalities and crash involvements were extracted from the Fatality Analysis Reporting System and General Estimates System. Poisson regression examined if pedestrian fatalities by various roadway, environmental, personal, and vehicle factors changed significantly during 2009–2016. Linear regression examined changes over the study period in pedestrian deaths per 100 crash involvements and in horsepower per 1000 pounds of weight among passenger vehicles involved in fatal single-vehicle pedestrian crashesResultsPedestrian deaths per 100 crash involvements increased 29% from 2010, when they reached their lowest point, to 2015, the most recent year for which crash involvement data were available. The largest increases in pedestrian deaths during 2009–2016 occurred in urban areas (54% increase from 2009 to 2016), on arterials (67% increase), at nonintersections (50% increase), and in dark conditions (56% increase). The rise in the number of SUVs involved in fatal single-vehicle pedestrian crashes (82% increase) was larger than the increases in the number of cars, vans, pickups, or medium/heavy trucks involved in these crashes. The power of passenger vehicles involved in fatal single-vehicle pedestrian crashes increased over the study period, with larger increases in vehicle power among more powerful vehicles.ConclusionsEfforts to turn back the recent increase in pedestrian fatalities should focus on the conditions where the rise has been the greatest.Practical applicationsTransportation agencies can improve urban arterials by investing in proven countermeasures, such as road diets, median crossing islands, pedestrian hybrid beacons, and automated speed enforcement. Better road lighting and vehicle headlights could improve pedestrian visibility at night.     

Land-traffic crash leading to passenger vehicle submersion,drowning and other fatal injuries: A 44-year study based on records from the Finnish Crash Data Institute

Background: Land motor traffic crash (LMTC) -related drownings are an overlooked and preventable cause of injury death. The aim of this study was to analyze the profile of water-related LMTCs involving passenger cars and leading to drowning and fatal injuries in Finland, 1972 through 2015. Materials and methods: The database of the Finnish Crash Data Institute (FCDI) that gathers detailed information on fatal traffic accidents provided records on all LMTCs leading to drowning during the study period and, from 2002 to 2015, on all water-related LMTCs, regardless of the cause of death. For each crash, we considered variables on circumstances, vehicle, and fatality profiles. Results: During the study period, the FCDI investigated 225 water-related LMTCs resulting in 285 fatalities. The majority of crashes involved passenger cars (124), and the cause of death was mostly drowning (167). Only 61 (36.5%) fatalities suffered some–generally mild–injuries. The crashes frequently occurred during fall or summer (63.7%), in a river or ditch (60.5%), and resulted in complete vehicle’s submersion (53.7 %). Half of the crashes occurred in adverse weather conditions and in over 40% of the cases, the driver had exceeded the speed limit. Among drivers, 77 (68.8%) tested positive for alcohol (mean BAC 1.8%). Conclusion: Multidisciplinary investigations of LMTCs have a much higher potential than do exclusive police and medico-legal investigations. The risk factors of water-related LMTCs are similar to those of other traffic crashes. However, generally the fatal event in water-related LMTC is not the crash itself, but drowning. The paucity of severe physical injuries suggests that victims’ functional capacity is usually preserved during vehicle submersion. Practical Applications: In water-related LMTCs, expansion of safety measures is warranted from general traffic-injury prevention to prevention of drowning, including development of safety features for submerged vehicles and simple self-rescue protocols to escape from a sinking vehicle.     

Investigation of injury severities in single-vehicle crashes in North Carolina using mixed logit models

IntroductionRoadway departure (RwD) crashes, comprising run-off-road (ROR) and cross-median/centerline head-on collisions, are one of the most lethal crash types. According to the FHWA, between 2015 and 2017, an average of 52 percent of motor vehicle traffic fatalities occurred each year due to roadway departure crashes. An avoidance maneuver, inattention or fatigue, or traveling too fast with respect to weather or geometric road conditions are among the most common reasons a driver leaves the travel lane. Roadway and roadside geometric design features such as clear zones play a significant role in whether human error results in a crash. Method: In this paper, we used mixed-logit models to investigate the contributing factors on injury severity of single-vehicle ROR crashes. To that end, we obtained five years' (2010–2014) of crash data related to roadway departures (i.e., overturn and fixed-object crashes) from the Federal Highway Administration's Highway Safety Information System Database. Results: The results indicate that factors such as driver conditions (e.g., age), environmental conditions (e.g., weather conditions), roadway geometric design features (e.g., shoulder width), and vehicle conditions significantly contributed to the severity of ROR crashes. Conclusions: Our results provide valuable information for traffic design and management agencies to improve roadside design policies and implementing appropriately forgiving roadsides for errant vehicles. Practical applications: Our results show that increasing shoulder width and keeping fences at the road can reduce ROR crash severity significantly. Also, increasing road friction by innovative materials and raising awareness campaigns for careful driving at daylight can decrease the ROR crash severity.     

The effectiveness of electronic stability control in reducing real-world crashes: a literature review

OBJECTIVE: Electronic stability control (ESC) is designed to help drivers maintain heading control of their vehicles in high-speed or sudden maneuvers and on slippery roads. The wider proliferation of ESC across the vehicle fleet has allowed evaluation of its effects in real-world crashes in many countries, including Japan, Germany, Sweden, France, Great Britain, and the United States. This article provides a summary of the findings. METHODS: Studies that examined the real-world effectiveness of ESC were reviewed. Crash effects have been examined for different roadways, using differing analytic methods, different crash severities, and different make/model vehicles including both cars and SUVs. The review discusses the methodological differences and examines the findings according to vehicle type, crash type and severity, and road conditions. RESULTS: The overwhelming majority of studies find that ESC is highly effective in reducing single-vehicle crashes in cars and SUVs. Fatal single-vehicle crashes involving cars are reduced by about 30-50% and SUVs by 50-70%. Fatal rollover crashes are estimated to be about 70-90% lower with ESC regardless of vehicle type. A number of studies find improved effectiveness in reducing crashes when road conditions are slippery. There is little or no effect of ESC in all multi-vehicle crashes; however, there is a 17-38% reduction in more serious, fatal multi-vehicle crashes. CONCLUSIONS: Given the extraordinary benefits of ESC in preventing crashes, especially those with more serious outcomes, the implementation of ESC should be accelerated to cover the full range of passenger vehicles in both developed and developing markets.     

An evaluation of the association between vehicle type and the source and severity of pedestrian injuries

To evaluate the effect of vehicle type (passenger vehicle vs. light truck vehicle) on crash trajectory and on the consequent source and severity of pedestrian injury, we analyzed data from the Pedestrian Crash Data Study (PCDS), conducted by National Highway Traffic Safety Administration (NHTSA) from 1994 to 1998. While 62% of the adults in PV (passenger vehicle)-related crashes were carried by the vehicle, such pedestrian-vehicle interaction was observed only in 28% of LTV (light truck vehicle)-adult crashes. Being thrown forward or knocked down were the most common (65%) type of pedestrian-vehicle interactions for LTV-adult crashes. For children, 93% of those struck by LTVs and 46% of those struck by PVs were thrown forward or knocked down. For adults, LTVs were more likely than PVs to cause thorax (37% vs. 20%) and abdomen injuries (33% vs. 18%). For children, LTVs were more likely than PVs to cause injuries to the upper extremity (71% vs. 56%) and abdomen (14% vs. 8%). For adults struck by PVs the most common sources of injury were windshield for head injuries (63%), hood surface for thorax (67%), abdomen (58%), spine (30%), and upper extremity (36%) injuries, and bumper for the lower extremity injuries (60%). The leading causes of injury for adult-LTV crashes were ground for head (39%) and upper extremity (37%) injuries, hood edge for thorax (48%) and abdomen (56%) injuries, hood surface for spine injuries (36%), and bumper for lower extremity injuries (45%). For child-PV crashes, ground was the most common source of face (37%) abdomen (83%), spine (43%), and upper extremity injuries (54%). For children hit by LTVs, 52% of face, 67% of abdomen, 100% of spine, and 60% of upper extremity injuries were attributed to ground contacts. Altogether, the major sources of injury were hood surface and windshield for PV-pedestrian crashes and hood surface and hood edge for LTV-pedestrian crashes. Changes in design, such as altering the geometry and stiffness of front-end structures, might be associated with considerable decrease in the frequency and severity of pedestrian injury.     

Characteristics of rear-end crashes involving passenger vehicles with automatic emergency braking

Abstract

Objectives: Automatic emergency braking (AEB) is a proven effective countermeasure for preventing front-to-rear crashes, but it has not yet fully lived up to its estimated potential. This study identified the types of rear-end crashes in which striking vehicles with AEB are overrepresented to determine whether the system is more effective in some situations than in others, so that additional opportunities for increasing AEB effectiveness might be explored.

Methods: Rear-end crash involvements were extracted from 23?U.S. states during 2009–2016 for striking passenger vehicles with and without AEB among models where the system was optional. Logistic regression was used to examine the odds that rear-end crashes with various characteristics involved a striking vehicle with AEB, controlling for driver and vehicle features.

Results: Striking vehicles were significantly more likely to have AEB in crashes where the striking vehicle was turning relative to when it was moving straight (odds ratio [OR]?=?2.35; 95% confidence interval [CI], 1.76, 3.13); when the struck vehicle was turning (OR = 1.66; 95% CI, 1.25, 2.21) or changing lanes (OR = 2.05; 95% CI, 1.13, 3.72) relative to when it was slowing or stopped; when the struck vehicle was not a passenger vehicle or was a special use vehicle relative to a car (OR = 1.61; 95% CI, 1.01, 2.55); on snowy or icy roads relative to dry roads (OR = 1.83; 95% CI, 1.16, 2.86); or on roads with speed limits of 70+ mph relative to those with 40 to 45?mph speed limits (OR = 1.49; 95% CI, 1.10, 2.03). Overall, 25.3% of crashes where the striking vehicle had AEB had at least one of these overrepresented characteristics, compared with 15.9% of strikes by vehicles without AEB.

Conclusions: The typical rear-end crash occurs when 2 passenger vehicles are proceeding in line, on a dry road, and at lower speeds. Because atypical crash circumstances are overrepresented among rear-end crashes by striking vehicles with AEB, it appears that the system is doing a better job of preventing the more typical crash scenario. Consumer information testing programs of AEB use a test configuration that models the typical rear-end crash type. Testing programs promoting good AEB performance in crash circumstances where vehicles with AEB are overrepresented could guide future development of AEB systems that perform well in these additional rear-end collision scenarios.     

Efficacy of side airbags in reducing driver deaths in driver-side car and SUV collisions

OBJECTIVE: To estimate the efficacy of side airbags in preventing driver deaths in passenger vehicles struck on the driver side. METHODS: Risk ratios for driver deaths per driver-side collision were computed for side airbag-equipped cars and SUVs, relative to vehicles without side airbags. Driver fatality ratios also were calculated for the same vehicles in front and rear impacts, and these were used to adjust the side crash risk ratios for differences in fatality risk unrelated to side airbags. Risk ratios were calculated separately for side airbags providing torso-only protection and side airbags with head protection; almost all head protecting airbags also had airbags protecting the torso. RESULTS: Car driver death risk in driver-side crashes was reduced by 37 percent for head protecting airbags and 26 percent for torso-only side airbags. Car driver death risk was reduced for older and younger drivers, males and females, and drivers of small and midsize cars, and when the striking vehicle was an SUV/pickup or a car/minivan. Death risk for drivers of SUVs was reduced by 52 percent with head protecting side airbags and by 30 percent with torso-only airbags. The effectiveness of side airbags could not be assessed for pickups and minivans due to the small number of these vehicles with airbags involved in crashes. CONCLUSION: Side airbags substantially reduce the risk of car and SUV driver death in driver-side collisions. Making side airbags with head protection available to drivers and right front passengers in all passenger vehicles could reduce the number of fatalities in motor vehicle crashes in the United States by about 2,000 each year.     

Vehicles driven by teenagers in their first year of licensure

OBJECTIVE: to determine access to vehicles, vehicle ownership and its correlates, and types of vehicles driven by teenagers during their first year of licensure. METHODS: About 3,500 Connecticut teenagers and their parents recruited at DMV offices participated in a study aimed at persuading parents to impose and maintain driving restrictions on their sons and daughters. Telephone interviews with teens and parents, which included questions on vehicles driven, were conducted upon licensure and at intervals throughout the year. RESULTS: The majority of both male and female teens owned vehicles immediately upon licensure. Family income and number of vehicles in the family were associated with early ownership. A year later 74% owned vehicles. Small cars, which provide inferior crash protection, were the most popular vehicle; the percent driving small cars increased from 36% to 42% over the year. About 25% were driving SUVs, pickups, or sports cars, which may increase crash risk for young beginners. One year after licensure, only 35% of teens were driving midsize or large passenger cars, the types of vehicles recommended for them, and about one-third of these vehicles were 10 or more years old. Owners were more likely than non-owners to drive older and smaller vehicles, to drive more miles, do more risky driving, and to have more traffic violations and crashes. DISCUSSION: Many teenagers in Connecticut were driving vehicles that rank low in crash protection or may increase crash risk. Attention to the young driver problem has been focused primarily on managing driving risks through graduated licensing systems. More attention needs to be given to the vehicles teens drive, and how decisions about vehicle type and ownership are made. Parents exert control over what vehicles their sons and daughters drive, and may benefit from information on how to make choices that better balance cost, safety, and other factors that go into these decisions.     

Effects of lane departure warning on police-reported crash rates

ObjectiveTo evaluate the effects of lane departure warning (LDW) on single-vehicle, sideswipe, and head-on crashes.MethodPolice-reported data for the relevant crash types were obtained from 25 U.S. states for the years 2009–2015. Observed counts of crashes with fatalities, injuries, and of all severities for vehicles with LDW were compared with expected counts based on crash involvement rates for the same passenger vehicles without LDW, with exposure by vehicle series, model year, and lighting system standardized between groups. For relevant crashes of all severities and those with injuries, Poisson regression was used to estimate the benefits of LDW while also controlling for demographic variables; fatal crashes were too infrequent to be modeled.ResultsWithout accounting for driver demographics, vehicles with LDW had significantly lower involvement rates in crashes of all severities (18%), in those with injuries (24%), and in those with fatalities (86%). Adding controls for driver demographics in the Poisson regression reduced the estimated benefit of LDW only modestly in crashes of all severities (11%, p < 0.05) and in crashes with injuries (21%, p < 0.07).ConclusionsLane departure warning is preventing the crash types it is designed to address, even after controlling for driver demographics. Results suggest that thousands of lives each year could be saved if every passenger vehicle in the United States were equipped with a lane departure warning system that performed like the study systems.Practical applicationsPurchase of LDW should be encouraged, and, because drivers do not always keep the systems turned on, future efforts should focus on designing systems to encourage greater use and educating consumers about the benefits of using the systems.     

Rating the Aggressivity of Australian Passenger Vehicles Towards Other Vehicle Occupants and Unprotected Road Users

Two measures of aggressivity of Australian passenger vehicles have been developed. The first measures the aggressivity to occupants of other cars. This type of aggressivity rating is based on two-car crashes between passenger vehicles and measures the injury risk each make/model in the collisions poses to the drivers of the other vehicles. The second measures aggressivity to unprotected road users. These aggressivity ratings reflect the threat of severe injury to pedestrians, bicyclists and motorcyclists by die make/model of vehicle colliding with them. This analysis was based on nearly 102,000 drivers involved in tow-away crashes with the makes/models which were the focus of the study and on nearly 22,000 injured pedestrians, bicyclists, and motorcyclists. The results suggest that crasbworthiness and aggressivity are two different aspects of a vehicle's safety performance, with good performance on one dimension not necessarily being associated with good performance on the other.     

Comparison of Expected Crash and Injury Reduction from Production Forward Collision and Lane Departure Warning Systems

Objectives: The U.S. New Car Assessment Program (NCAP) now tests for forward collision warning (FCW) and lane departure warning (LDW). The design of these warnings differs greatly between vehicles and can result in different real-world field performance in preventing or mitigating the effects of collisions. The objective of this study was to compare the expected number of crashes and injured drivers that could be prevented if all vehicles in the fleet were equipped with the FCW and LDW systems tested under the U.S. NCAP.

Methods: To predict the potential crashes and serious injury that could be prevented, our approach was to computationally model the U.S. crash population. The models simulated all rear-end and single-vehicle road departure collisions that occurred in a nationally representative crash database (NASS-CDS). A sample of 478 single-vehicle crashes from NASS-CDS 2012 was the basis for 24,822 simulations for LDW. A sample of 1,042 rear-end collisions from NASS-CDS years 1997–2013 was the basis for 7,616 simulations for FCW. For each crash, 2 simulations were performed: (1) without the system present and (2) with the system present. Models of each production safety system were based on 54 model year 2010–2014 vehicles that were evaluated under the NCAP confirmation procedure for LDW and/or FCW. NCAP performed 40 LDW and 45 FCW tests of these vehicles.

Results: The design of the FCW systems had a dramatic impact on their potential to prevent crashes and injuries. Between 0 and 67% of crashes and 2 and 69% of moderately to fatally injured drivers in rear-end impacts could have been prevented if all vehicles were equipped with the FCW systems. Earlier warning times resulted in increased benefits. The largest effect on benefits, however, was the lower operating speed threshold of the systems. Systems that only operated at speeds above 20 mph were less than half as effective as those that operated above 5 mph with similar warning times. The production LDW systems could have prevented between 11 and 23% of drift-out-of-lane crashes and 13 and 22% of seriously to fatally injured drivers. A majority of the tested LDW systems delivered warnings near the point when the vehicle first touched the lane line, leading to similar benefits. Minimum operating speed also greatly affected LDW effectiveness.

Conclusions: The results of this study show that the expected field performance of FCW and LDW systems are highly dependent on the design and system limitations. Systems that delivered warnings earlier and operated at lower speeds may prevent far more crashes and injuries than systems that warn late and operate only at high speeds. These results suggest that future FCW and LDW evaluation should prioritize early warnings and full-speed range operation. A limitation of this study is that additional crash avoidance features that may also mitigate collisions—for example, brake assist, automated braking, or lane-keeping assistance—were not evaluated during the NCAP tests or in our benefits models. The potential additional mitigating effects of these systems were not quantified in this study.     

The effect of speed limit reductions in urban areas on cyclists’ injuries in collisions with cars

Abstract

Objective: Impact speed is one of the most important factors explaining the severity of injuries to cyclists when they collide with passenger cars. To reduce injury severity (especially for vulnerable road users), since 2008, Swedish municipalities have the authority to lower the speed limit to 30 or 40?km/h in urban areas as appropriate. The aim of this study was to evaluate how this speed limit reduction has influenced the injury severity for cyclists in this type of collision.

Method: Data from 1,953 collisions between bicycles and passenger cars were collected using information from third-party-liability insurance claims from 2005 to 2017. The change of speed limit distribution, influenced by the reduction of speed limits in urban areas, where car-to-cyclist collisions occurred was studied. Following that, injury severity for cyclists was evaluated regarding collisions occurring in areas with different speed limits.

Results: The results show that, in collisions with cars, cyclists have a significantly lower risk of a moderate-to-fatal (MAIS 2+) injury when the speed limit is 30–40?km/h compared to 50–60?km/h. During the last decade, while the speed-limit has been lowered on many road-sections in urban areas from 50–60?km/h to 30–40?km/h the risk of a cyclist getting a MAIS 2+ injury decreased by 25%. In 2005 to 2011, 16% of the crashes happened on a road with a speed limit of 30–40?km/h; in 2016–2017, this percentage had increased to approximately 50%. Thus, in recent years more crashes occurred on roads with lower speed limits, and in these crashes, there was a lower risk of severe injuries to cyclists. Unfortunately, it was not possible to evaluate the risk of a crash for specific speed limits; since one limitation of this study was the lack of exposure data, nor do we know the impact speed or the actual speed of the vehicles.

Conclusions: This study is an important follow-up on the implementation of measures that can influence bicycle safety. The insurance data used, made it possible to quantify a positive effect on injury severity for cyclists in passenger car-to-cyclist collisions when the speed limit was reduced in urban areas. Insurance claims cover collisions of all crash severity, so they include data covering all types of injuries—not just the most severe/fatal ones. This aspect is especially important in the speed intervals evaluated here, since moderate (MAIS 2) injuries are very frequent in lower-speed crashes and even these injuries can result in long-term consequences.     

Characteristics of vehicle-animal crashes in which vehicle occupants are killed

During the past 10 years almost 1,500 people have been killed in motor vehicle collisions with animals. Police reports on 147 fatal vehicle-animal crashes during 2000-2002 were obtained from nine states. The goal was to determine common crash types, types of animals involved, and steps that could be taken to reduce the crashes and injuries. Seventy-seven percent of the struck animals were deer, but six other types of animals were involved including small ones such as dogs. Eighty percent of the crashes were single-vehicle events. In most of these cases a motorcycle struck an animal and the rider came off the vehicle, or a passenger vehicle struck an animal and then ran off the road; in a few cases the animal went through the windshield. Multiple-vehicle crashes included vehicles striking deer that went through the windshields of oncoming vehicles, vehicles striking animals and then colliding with other vehicles, and vehicles striking animals that subsequently were struck by other vehicles. Crashes occurred primarily in rural areas, on roads with 55 mph or higher speed limits, during evening or nighttime hours, and in darkness. Greater application of deer-vehicle collision countermeasures known to be effective is needed, but it is noteworthy that a majority of fatalities occurred from subsequent collisions with other vehicles or objects, not from animal contacts. Sixty-five percent of motorcyclists killed were not wearing helmets, and 60% of vehicle occupants killed were unbelted; many of these fatalities would not have occurred with proper protection.