September 2017

  1. What does automation mean when it comes to driving?

    Automation is the use of a machine or technology to perform a task or function that was previously carried out by a human. Parasuraman, R. and Riley, V. 1997. Humans and automation: use, misuse, disuse, abuse. Human Factors 39:230-53. In driving, automation involves using radar, camera, and other sensors to perform parts or all of the driving task on a sustained basis instead of the driver. One example is adaptive cruise control, which continually adjusts the vehicle's speed to maintain a set minimum following distance. Features such as automatic braking, which acts as a back-up if the human driver fails to brake, or blind spot detection, which provides additional information to the driver, aren't considered automation under this definition.

  2. Will I still need to pay attention when using automation to drive my car?

    For the foreseeable future, yes. Driving automation is not limited to vehicles that drive themselves without human interaction, but includes technologies that vary in technical capability.

    The National Highway Traffic Safety Administration released policy guidelines in September 2016 for automated vehicles to clarify the technical differences between different levels of automation based on definitions developed by SAE International. National Highway Traffic Safety Administration. 2016. Federal automated vehicles policy: accelerating the next revolution in roadway safety. Washington, DC: U.S. Department of Transportation. SAE International. 2016. Surface vehicle recommended practice J3016; Taxonomy and definitions for terms related to on-road motor vehicle automated driving systems. Warrenton, PA. The levels of driving automation range from none, or Level 0, to full driving automation, or Level 5. The levels are differentiated by whether a human is required to monitor the driving environment and whether, if things go wrong, the human is expected to take control or the automated system can bring the vehicle safely to a stop.

    Levels of driving automation:

    • Level 0: The human driver does everything.
    • Level 1: An automated system can assist the human driver in conducting some parts of the driving task.
    • Level 2: An automated system can assist the driver with multiple parts of the driving task. The driver must continue to monitor the driving environment and be actively engaged.
    • Level 3: An automated system conducts some parts of the driving task without driver engagement and monitors the driving environment, but the human driver must stand by to intervene.
    • Level 4: An automated system can conduct the driving task and monitor the driving environment but would be limited to operating in certain environments and under certain conditions. If something goes wrong with the system or the vehicle reaches the limits of its operating environment or conditions, the vehicle would stop itself safely if the human driver is unable to take over.
    • Level 5: An automated system can perform the entire driving task without driver input under all conditions.

    In vehicles in which only some parts of the driving task, such as steering, controlling speed or following distance, or braking, are automated (Levels 1-2), drivers are still expected to be actively engaged and to continuously monitor the driving environment. Adaptive cruise control and Tesla's Autopilot software are examples of Level 1 and Level 2 systems.

    In contrast, drivers aren't expected to be actively engaged when using automated systems that monitor the environment in addition to performing some or all parts of the driving task (levels 3-5). However, some of these systems may rely on the driver to intervene if something goes wrong (Level 3) while others may stop the vehicle safely if the driver is unable to take over (levels 4 and 5).

    So far, all of this technology is constrained to specific road and environmental conditions, so drivers will be expected to bridge the gap until full driving automation is developed that can perform the entire driving task without driver input under all conditions (Level 5).

  3. Will automation reduce motor vehicle deaths and injuries?

    The potential injury and fatality reductions associated with driving automation are huge. An in-depth study of police-reported crashes occurring during 2005-07 where at least one vehicle was towed from the scene concluded that a driver's error or physical state led to 94 percent of the crashes. Singh, S. 2015. Critical reasons for crashes investigated in the National Motor Vehicle Crash Causation Survey. Traffic Safety Facts, Report no. DOT HS 812 115. Washington, DC: National Highway Traffic Safety Administration. If automation can eliminate all crashes involving driver-related factors, then thousands of lives could be saved each year — but that's a big "if."

    Already, crash avoidance features that use some of the same sensing and control technologies that underpin automation, are preventing crashes. Automatic braking, lane departure warning, blind spot detection and electronic stability control, for example, have been shown to prevent crashes. Cicchino, J.B. 2016. Effects of blind spot monitoring systems on police-reported crash rates. Arlington, VA: Insurance Institute for Highway Safety. Cicchino, J.B. 2016. Effects of lane departure warning on police-reported crash rates. Arlington, VA: Insurance Institute for Highway Safety. Cicchino, J.B. 2017. Effectiveness of forward collision warning and autonomous emergency braking systems in reducing front-to-rear crash rates. Accident Analysis and Prevention, 99, 142-152. Farmer, C.M. 2010. The effect of electronic stability control on fatal crash risk. Arlington, VA: Insurance Institute for Highway Safety. Highway Loss Data Institute. 2012. Summary of ESC’s effectiveness in cars, SUVs, and pickups. HLDI Bulletin 29(24). Arlington, VA. Highway Loss Data Institute. 2014. Electronic stability control and the vehicle fleet. HLDI Bulletin 31(13). Arlington, VA. Highway Loss Data Institute. 2015a. Volvo City Safety loss experience: along-term update. HLDI Bulletin 32(1). Arlington, VA. Highway Loss Data Institute. 2015b. 2013-2015 Honda Accord collision avoidance features. HLDI Bulletin 32(33). Arlington, VA. Highway Loss Data Institute. 2016a. Mercedes-Benz collision avoidance features: a 2016 update. HLDI Bulletin 33(23). Arlington, VA. Highway Loss Data Institute. 2016b. Acura collision avoidance features: a 2016 update. HLDI Bulletin 33(19). Arlington, VA. Highway Loss Data Institute. 2016c. Subaru collision avoidance features: an update. HLDI Bulletin 33(6). Arlington, VA.

    Much of the automation available in current vehicles such as adaptive cruise control and lane-keeping support, typically works only on higher speed roadways where crashes are relatively infrequent. Even if all interstate miles were logged by vehicles driven entirely by automation that did not crash, the maximum overall benefit would be 17 percent fewer crash deaths and 9 percent fewer crash injuries, based on an Institute estimate using 2014 crash data. Insurance Institute for Highway Safety. 2016. Special issue: autonomous vehicles. Status Report 51(8). Arlington, VA. More advanced forms of automation that operate more broadly could potentially prevent far more crashes, but it is still too early to tell if these technologies will live up to expectations.

    An Institute analysis compared crash rates for Google's prototype vehicles with high levels of driving automation with police-reported crash rates in the same geographic location, specifically Mountain View before 2016. Teoh, E.R. & Kidd, D.G. (in press). Rage against the machine? Google’s self-driving cars versus human drivers. Journal of Safety Research. Of 10 crashes Google reported to California officials, three were severe enough that they would have been reported to police had they involved only human drivers. That yielded a crash rate of 2.19 crashes per million miles traveled while automation was being used. This is considerably lower than the police-reported crash rate in Mountain View, (6.06 per million vehicle miles traveled), where Google cars operate, and comparable to the statewide rate in California (1.92 per million vehicle miles traveled). Two other studies that attempted to determine if Google's vehicles had lower crash rates than conventional vehicles found mixed results. Schoettle, B. and Sivak, M. 2015. A preliminary analysis of real-world crashes involving self-driving vehicles. Report no. UMTRI-2015-34. Ann Arbor, MI: University of Michigan Transportation Research Institute.  Blanco, M.; Atwood, J.; Russel, S.; Trimble, T.; McClafferty, J.; and Perez, M. 2016. Automated vehicle crash rate comparison using naturalistic data. Blacksburg, VA: Virginia Tech Transportation Institute.

  4. Are there laws or regulations governing the use or deployment of driving automation?

    Yes. Regulatory frameworks for testing and deploying self-driving cars are being developed in the United States and abroad. Council of the European Union. 2016. Declaration of Amsterdam; Cooperation in the field of connected and automated driving. Amsterdam, Netherlands. National Highway Traffic Safety Administration. 2016. Federal automated vehicles policy: accelerating the next revolution in roadway safety. Washington, DC: U.S. Department of Transportation.

    In 2011, Nevada became the first state to enact legislation specifically permitting research and testing of limited and full self-driving autonomous vehicles on public roads. Today, 22 states and the District of Columbia have enacted legislation or issued executive orders addressing driving automation. The laws in six of those states (Alabama, Louisiana, North Dakota, Pennsylvania, Vermont and Wisconsin) simply authorize a study, define key terms or authorize funding. Six states authorize testing, while 10 states and D.C. authorize full deployment.

    More information on Automation Laws

    By executive order, Arizona authorizes pilot programs on campuses of selected universities. Massachusetts has formed a working group to develop legislation and approve companies who wish to test autonomous technology. Tennessee prohibits barring the use of vehicles equipped with autonomous technology if the vehicle otherwise complies with safety standards. Four additional states (Alabama, Louisiana, North Dakota and Utah) have enacted study requirements or autonomous definitions within the state code.  

    Other states are forming working groups to develop policies on autonomous vehicles, enacting study requirements or inserting driving automation definitions into the state code. Still others have openly welcomed testing on public roads without legislation or regulatory action.

    In September 2016, the National Highway Traffic Administration released model policy guidance to help state lawmakers address testing and deployment of automated vehicle technology and encourage a consistent legislative approach nationwide. National Highway Traffic Safety Administration. 2016. Federal automated vehicles policy: accelerating the next revolution in roadway safety. Washington, DC: U.S. Department of Transportation.

  5. When will my car drive itself?

    Vehicles that drive themselves without human involvement will first be available as part of taxi and ride-sharing services. In August 2016, the world's first taxi service featuring high levels of driving automation debuted in Singapore. Watts, J.M. 2016. World's first self-driving taxis hit the road in Singapore. The Wall Street Journal, August 25. New York, NY: News Corp. Uber allows select customers in Pittsburgh and Tempe, Ariz., to hail a vehicle that drives itself with a human supervisor, marking the first time the public can ride in this type of vehicle in the United States. Hawkins, A.J. 2017. Uber’s self-driving cars are now picking up passengers in Arizona. The Verge, February 21. Retrieved March 23, 2017 from http://www.theverge.com/2017/2/21/14687346/uber-self-driving-car-arizona-pilot-ducey-california Ford and Lyft separately plan on introducing vehicles with high levels of automation for ride sharing in 2021. Ford Motor Company Media Center. 2016. Ford targets fully autonomous vehicle for ride sharing in 2021; Invests in new tech companies, doubles Silicon Valley team. Dearborn, MI: Ford Motor Company. Covert, J. 2016. Lyft predicts mostly self-driving cars by 2021. New York Post, September 19. New York, NY: News Corp.

    Automakers have provided different target dates for when highly automated vehicles will be available for purchase by consumers. Some companies have claimed high or full driving automation will be available in 2020 Woodyard, C. 2016. Two auto suppliers join for self-driving cars by 2019. USA Today, August 23. McLean, VA: Gannett Company. or 2021 Mobileye. 2016. BMW Group, Intel and Mobileye team up to bring fully autonomous driving to streets by 2021. News Release, July 1. Jerusalem, Israel. while others promise this level of automation by 2030. Martinez, M. 2016. Kia plans fully driverless cars by 2030. The Detroit News, January 5. Detroit, MI; Digital First Media.

    Regardless of when vehicles equipped with high levels of automation become available for purchase, it will be decades before most vehicles on the road drive themselves. It takes a long time for new vehicle features to penetrate the vehicle fleet. For example, electronic stability control was introduced in the United States in 1995 model year vehicles, but it was not until nearly 20 years later in the 2012 model year that it became standard in over 95 percent of new vehicle models. Highway Loss Data Institute. 2016d. Predicted availability of safety features on registered vehicles: a 2016 update. HLDI Bulletin 33(15). Arlington, VA. More recent crash avoidance technologies like front crash prevention and lane departure warning are not expected to be in nearly all registered vehicles on the nation's roadways until after 2040. Highway Loss Data Institute. 2016d. Predicted availability of safety features on registered vehicles: a 2016 update. HLDI Bulletin 33(15). Arlington, VA. It will be even longer before most registered vehicles in the U.S. are equipped with Level 2 automation that is just now becoming available in vehicles today. Highway Loss Data Institute. 2016d. Predicted availability of safety features on registered vehicles: a 2016 update. HLDI Bulletin 33(15). Arlington, VA.

  6. With all this automation, will it still be necessary to learn how to drive?

    Full automation is still years away, so people will need to know how to drive for now.  The automated systems currently available on vehicles perform only parts of the driving task in certain situations.

    In fact, these recent innovations may require additional training. Drivers need to know when automation is available, how to use it and how to take control when automation is no longer available or if it fails. Experimental studies have shown that drivers can lose sight of what automated systems are doing, fail to notice when something goes wrong, and have trouble taking control again. Endsley, M.R. and Kiris, E.O. 1995. The out-of-the-loop performance problem and level of control in automation. Human Factors 37:381-94. Gold, C.; Körber, M.; Lechner, D.; and Bengler, K. 2016. Taking over control from highly automated vehicles in complex traffic situations: the role of traffic density. Human Factors 58:642-52. German Insurers Accident Research (UDV) 2016. Takeover times in highly automated driving: compact accident research. Berlin, Germany: German Insurance Association (GDV). Haslbeck, A. and Hoermann, H. 2016. Flying the needles: flight deck automation erodes fine-motor flying skills among airline pilots. Human Factors 58:533-45. Lee, J.D. and See, K.A. 2004. Trust in automation: designing for appropriate reliance. Human Factors 45:50-80. Merat, N.; Jamson, A.H.; Lai, F.C.H.; Daly, M.; and Carsten, O.M.J. 2014. Transition to manual: driver behavior when resuming control from a highly automated vehicle. Transportation Research Part F: Traffic Psychology and Behaviour 27:274-82. Wickens, C.D.; Lee, J.D.; Liu, Y.; and Gordon-Becker, S. 2004. An Introduction to Human Factors Engineering (2nd ed.). Upper Saddle River, NJ: Pearson Prentice Hall. Zeeb, K.; Buchner, A.; and Schrauf, M. 2016. Is take-over time all that matters? The impact of visual-cognitive load on driver take-over quality after conditionally automated driving. Accident Analysis and Prevention 92:230-39.  Ruscio, D.; Ciceri, M.R.; and Biassoni, F. 2015. How does a collision warning system shape driver's brake response time? The influence of expectancy and automation complacency on real-life emergency braking. Accident Analysis and Prevention 77:72-81.

    People will not need to learn how to drive vehicles that can drive themselves safely without human involvement (Level 4 or 5), but only how to tell the vehicle where to go or what to do in an emergency.

August 2017

  1. What are crash avoidance technologies?

    The term "crash avoidance" can encompass a wide variety of vehicle features designed to help the driver operate the vehicle safely. Vehicles increasingly offer advanced technologies that assist the driver with warnings or automatic braking to avoid or mitigate a crash. These advanced technologies vary in their function and how they operate. In general, they monitor driver input and the environment around the vehicle and warn the driver when they detect the possibility of a collision. In some cases, they increase braking power or adjust steering response to make the driver’s input more effective. They also may automatically brake or steer the vehicle if the driver does not act to avoid the collision. 

  2. What kinds of crash avoidance technologies are currently available for passenger vehicles?

    This list summarizes some of the most common or promising crash avoidance systems. This is not a comprehensive list of technologies, as more are introduced each year. The descriptions are general and may not capture every variation of a given technology.

    Front crash prevention systems use various types of sensors, such as cameras, radar, or light detection and ranging (LIDAR) to detect when the vehicle is getting too close to one in front of it. Most systems issue a warning and precharge the brakes to maximize their effect if the driver brakes. Many systems brake the vehicle autonomously if the driver doesn't respond. In some cases, automatic braking is activated without a preliminary warning. An autobrake system may not always prevent a crash but may reduce vehicle speed, mitigating the severity of the crash.

    Some front crash prevention systems can recognize pedestrians, cyclists and animals. These systems use advanced algorithms coupled with sensors and cameras to spot nonmotorists who are in or about to enter the vehicle's path.

    Lane departure warning and lane-keeping support systems use cameras to track the vehicle's position within the lane, alerting the driver if the vehicle is in danger of inadvertently straying across lane markings when the turn signal is not activated. Some systems use haptic warnings, such as steering wheel or seat vibration, while others use audible and/or visual warnings. Some systems cause the vehicle to actively resist moving out of the lane or help direct the vehicle back into the lane through light braking or minor steering adjustments.

    Blind spot detection uses sensors to monitor the side of the vehicle for vehicles approaching blind spots. In many systems, a visual alert appears on or near the side mirrors if a vehicle is detected. An audible alert may activate if the driver signals a turn and there is a vehicle in the blind spot. Some systems also may activate the brake or steering controls to keep the vehicle in its lane.

    Park assist and backover prevention systems help drivers park and back up. Rear object detection systems use cameras and sensors to help the driver look for objects behind the vehicle when backing up. Rearview cameras display what is behind the vehicle. Systems that use radar or ultrasonic sensors, as well as some camera systems, warn the driver if there are objects in the way when the vehicle is in reverse. Some systems automatically apply the brakes to keep the vehicle from backing into or over an object. A cross-traffic alert system detects approaching vehicles that may cross the path of a backing vehicle, warns the driver, and may automatically brake to prevent a collision.

    • See the backover crashes Q&A for more information on the use of cameras to prevent backover crashes.

    Fatigue warning systems use sophisticated algorithms that monitor driver steering and other behaviors, such as the driver's eye blink rate or blink duration. A system alerts the driver if it detects inattention or drowsiness.

    Curve-adaptive headlights help drivers see better on dark, curved roads. The headlights pivot in the direction of travel based on steering wheel movement and sometimes the vehicle’s speed to illuminate the road ahead.

    Electronic stability control utilizes sensors and a microcomputer to monitor how well a vehicle responds to a driver's steering input. The system selectively applies the brakes and modulates the engine power to keep the vehicle traveling along the path indicated by the steering wheel position.

    Antilock brakes prevent wheels from locking up and skidding during hard braking by monitoring the speed of each wheel and automatically pulsing the brake pressure on any wheels where skidding is detected.

  3. Do crash avoidance features reduce crashes?

    Many technologies are proving effective in the real world.

    Vehicles equipped with front crash prevention are much less likely to rear-end other vehicles than the same models without the technology. Fildes, B.; Keall, M.; Bos, N.; Lie, A.; Page, Y.; Pastor, C.; Pennisi, L.; Rizzi, M.; Thomas, P.; and Tingcall, V. 2015. Effectiveness of low speed autonomous emergency braking in rear-world rear-end crashes. Accident Analysis & Prevention, 81, 24-29. Isaksson-Hellman, I. and Lindman, M. 2016. Evaluation of the crash mitigation effect of low-speed automated emergency braking systems based on insurance claims data. Traffic Injury Prevention, Sup 1, 42-47. Cicchino, Jessica B. 2017. Effectiveness of forward collision warning and autonomous emergency braking systems in reducing front-to-rear crash rates. Accident Analysis and Prevention, 99: 142-152. An Institute study found that systems with forward collision warning and automatic braking cut rear-end crashes in half, while forward collision warning alone reduces them by 27 percent. The autobrake systems also greatly reduce rear-end crashes involving injury.

    The Highway Loss Data Institute (HLDI) conducted similar studies comparing insurance claim rates for vehicles equipped with front crash prevention with claim rates for the same models without the technology. Vehicles equipped with these systems consistently show lower rates of claims for damage to other vehicles and for injuries to people in other vehicles. Highway Loss Data Institute. 2016. Mercedes-Benz collision avoidance features: a 2016 update. HLDI Bulletin 22(23). Highway Loss Data Institute. 2016. Acura collision avoidance features: an update. HLDI Bulletin 33(19). Highway Loss Data Institute. 2012. Volvo collision avoidance features: initial results. HLDI Bulletin 29(5). Highway Loss Data Institute. 2016. Mazda collision avoidance features: an update. HLDI Bulletin 33(3). Highway Loss Data Institute. 2016. 2013-2015 Honda Accord collision avoidance features. HLDI Bulletin, 33(32). Highway Loss Data Institute. 2017. 2013-16 Subaru collision avoidance features. HLDI Bulletin, 34(10). Highway Loss Data Institute. 2015. Volvo City Safety loss experience – a long-term update. HLDI Bulletin, 32(1). Highway Loss Data Institute. 2016. Fiat Chrysler collision avoidance features: initial results. HLDI Bulletin, 33(2). Highway Loss Data Institute. 2017. Honda Odyssey collision avoidance features: initial results. HLDI Bulletin, 34(15). Highway Loss Data Institute. 2017. 2016 Honda collision avoidance features: initial results. HLDI Bulletin, 34(7).

    Blind spot detection has been show to reduce lane-change crashes by 14 percent. Cicchino, J.B. 2017. Effects of blind spot monitoring systems on police-reported lane-change crashes. Arlington, VA: Insurance Institute for Highway Safety. HLDI research has also found that blind spot detection lowers rates of insurance claims covering damage to other vehicles. Highway Loss Data Institute. 2016. Mercedes-Benz collision avoidance features: a 2016 update. HLDI Bulletin 22(23). Highway Loss Data Institute. 2016. Acura collision avoidance features: an update. HLDI Bulletin 33(19). Highway Loss Data Institute. 2012. Volvo collision avoidance features: initial results. HLDI Bulletin 29(5). Highway Loss Data Institute. 2011. Mazda collision avoidance features: initial results. HLDI Bulletin 28(13). Highway Loss Data Institute. 2017. 2013-16 Subaru collision avoidance features. HLDI Bulletin, 34(10). Lane departure warning has not brought down insurance claim rates, but has reduced rates of single-vehicle, sideswipe, and head-on crashes reported to the police. Highway Loss Data Institute. 2016. Mercedes-Benz collision avoidance features: a 2016 update. HLDI Bulletin 22(23). Highway Loss Data Institute. 2011. Mazda collision avoidance features: initial results. HLDI Bulletin 28(13). Cicchino, J.B. 2017. Effects of lane departure warning on police-reported crash rates. Arlington, VA: Insurance Institute for Highway Safety. Sternlund, S.; Strandroth, J.; Rizzi, M.; Lie, A.; and Tingvall, C 2017. The effectiveness of lane departure warning systems—a reduction in real-world passenger car injury crashes. Traffic Injury Prevention, 18, 225-229.

    Rearview cameras are effective in preventing backing crashes reported to the police, which are often crashes in which a vehicle backs into another vehicle. Cicchino, J.B. In press. Effects of rearview cameras and rear parking sensors on police-reported backing crashes. Traffic Injury Prevention. The effects of rearview cameras on insurance claims has been less clear. Vehicles with rearview cameras tend to show lower rates of claims for damage caused to other vehicles, but some systems also have higher rates of claims covering damage to their own vehicle. Rear parking sensors have reduced insurance claims but have had inconsistent effects on back crashes reported to the police. Highway Loss Data Institute. 2016. Mercedes-Benz collision avoidance features: a 2016 update. HLDI Bulletin 22(23). Highway Loss Data Institute. 2016. Buick collision avoidance features: an update. HLDI Bulletin 33(18). Cicchino, J.B. In press. Effects of rearview cameras and rear parking sensors on police-reported backing crashes. Traffic Injury Prevention.

  4. If a crash avoidance system doesn't prevent a crash, can it still be beneficial?

    In some cases, yes. Even if a front crash prevention system doesn't avoid a crash altogether, it may still reduce the impact speed, thereby making a crash less severe. To show why reducing speed is important, IIHS conducted two demonstration crash tests at different speeds. In each test, a 2013 Mercedes-Benz C-Class ran into the back of a stationary 2012 Chevrolet Malibu. The tests illustrate what happens in a 25 mph crash when the striking vehicle doesn't have autobrake, compared with what happens when the speed is reduced by 13 mph, the amount by which the C-Class's autobrake system reduced the impact speed in IIHS track testing. Damage in the higher speed crash test was about $28,000. The Malibu was a complete loss. Lowering the speed to 12 mph trimmed the damage to $5,700. Insurance Institute for Highway Safety. 2013. Crash tests show how autobrake can mitigate crash severity, damage costs. Status Report 48(7):5. A similar speed reduction in a higher speed crash could significantly reduce injury risk, as well as vehicle damage. Krafft, M.; Kullgren, A.; Lie., A.; Strandroth, J.; & Tingvall, C. 2009. The effects of automatic emergency braking on fatal and serious injuries. Proceedings of the 21st International Technical Conference on the Enhanced Safety of Vehicles.

    Front crash prevention systems with automatic braking have resulted in bigger reductions in rear-end crashes with injuries than in rear-end crashes of all severities, which suggests that these systems are preventing injuries in some rear-end crashes that aren't avoided. Cicchino, Jessica B. 2017. Effectiveness of forward collision warning and autonomous emergency braking systems in reducing front-to-rear crash rates. Accident Analysis and Prevention, 99: 142-152. The same is true for lane departure warning and blind spot detection systems, where reductions in injury crashes relevant to the systems are larger than reductions in relevant crashes of all severities. Cicchino, J.B. 2017. Effects of lane departure warning on police-reported crash rates. Arlington, VA: Insurance Institute for Highway Safety. Cicchino, J.B. 2017. Effects of blind spot monitoring systems on police-reported lane-change crashes. Arlington, VA: Insurance Institute for Highway Safety. If crash avoidance systems only prevented injuries when crashes were avoided altogether, injury crash reductions would be expected to be the same or smaller than the reductions in crashes of all severities.

  5. What resources are available for consumers who want to purchase a vehicle with crash avoidance features?

    Advanced crash avoidance features started out as options on a few luxury vehicles and have steadily spread to more of the fleet, including many nonluxury models. Front crash prevention is likely to become even more prevalent. In March 2016, the National Highway Traffic Safety Administration (NHTSA) and IIHS announced a commitment of 20 major automakers, representing 99 percent of U.S. light vehicle sales, to make front crash prevention systems standard on virtually all models by September 2022.

    Information by make and model on the availability of forward collision warning, autobrake, lane departure warning, lane departure prevention, adaptive headlights and blind spot detection can be found here.

    An Institute test program rates the performance of headlights and front crash prevention systems to help consumers compare them and to encourage automakers to speed adoption of the technology. Information on IIHS ratings can be found here.

    In addition to forward collision warning, NHTSA has recognized the potential importance of lane departure warning systems and rear-view video systems for backover prevention by incorporating them into its New Car Assessment Program. Vehicles are credited with having these systems if their system can pass performance specifications.

  6. How do drivers respond to crash avoidance features?

    Appropriate driver responses and acceptance of crash avoidance technologies are critical to their success. If drivers don't trust the systems or find them annoying or not useful, they may disable them. Similarly, if drivers experience warnings but don't understand them, are overwhelmed by them, or don't take an appropriate corrective action, then the systems will be ineffective.

    Early research using simulators has shown collision warning systems can redirect the driver’s attention to the road and improve reaction time, but little is known about how drivers respond in real-world driving. Lee, J.D.; McGehee, D.V.; Brown, T.L.; and Reyes, M.L. 2002. Collision warning timing, driver distraction, and driver response to imminent rear-end collisions in a high-fidelity driving simulator. Human Factors 44(2): 314-34.

    Institute surveys of owners of vehicles with crash avoidance technologies found that, despite some annoyance about false alerts, for example, most drivers left the systems turned on most of the time, felt the systems made them safer drivers and would want them in their next vehicle. Braitman, K.A.; McCartt, A.T.; Zuby, D.S.; and Singer, J. 2010. Volvo and Infiniti drivers' experiences with select crash avoidance technologies. Traffic Injury Prevention 11(3):270-8. Eichelberger, A.H. and McCartt, A.T. 2014. Volvo drivers' experiences with advanced crash avoidance and related technologies. Traffic Injury Prevention 15(2):187-95. Cicchino, J.B. and McCartt, A.T. 2015. Experiences of model year 2011 Dodge and Jeep owners with collision avoidance and related technologies. Traffic Injury Prevention 16(3):298-303. Eichelberger, A.H. and McCartt, A.T. 2016. Toyota drivers' experiences with Dynamic Radar Cruise Control, Pre-Collision System, and Lane-Keeping Assist. Journal of Safety Research 56:67-73. Observations at dealerships of seven automakers in 2016 found that front crash prevention systems were activated in 93 percent of the vehicles obeserved that arrived for service, and nearly 100 percent of the blind spot monitoring and rear-cross traffic alert systems were turned on. Reagan, Ian J.; Cicchino, J.B.; Kerfoot, L.B.; and Weast, R.A. 2017. Crash avoidance and driver assistance technologies - are they used?. Arlington, VA: Insurance Institute for Highway Safety. Activation of lane departure warning and lane keeping-support systems were much lower at 51 percent. Lane departure systems that warned by vibration were more likely to be activated than those that beeped, and lane-keeping systems were more likely to be turned on than warning-only systems.

    In 2016, the Institute conducted a research program with four production vehicles with advanced crash avoidance and driver assist features. Volunteer employees drove at least one vehicle for up to two weeks and later completed surveys about their experience with the technologies. The results show that opinions varied among types of systems and among vehicles. For example, drivers trusted blind spot monitoring more than lane departure warning and trusted Infiniti's blind spot monitoring system less than Honda's or Audi's. Kidd, D.G., Cicchino, J.B.; Reagan, I.J.; and Kerfoot, L.B. 2016. Driver trust in five driver assistance technologies following real-world use in four production vehicles. Arlington, VA: Insurance Institute for Highway Safety.

    One concern is that drivers might rely on crash avoidance systems too much and feel freer to look away from the road or take other risks. In the Institute's surveys of owners of vehicles with various technologies, many owners reported safer driving habits with the systems (e.g., using turn signals more often with lane departure warning). Fewer owners reported potentially unsafe behavior, such as waiting for an alert before braking or allowing the vehicle to brake for them at least some of the time. An Institute naturalistic study monitored teens that drove vehicles with and without a suite of prototype collision avoidance systems, including forward collision warning and lane departure warning. When teens drove with the systems, turn signal use increased and lane drifts decreased, but the teens also followed other vehicles at close distances more often. Jermakian, J. S.; Bao, S.; Buonarosa, M. L.; Sayer, J. R.; and Farmer, C. M. 2017. Effects of an integrated collision warning system on teenage driver behavior. Journal of Safety Research, 61, 65-75.

  7. What are some of the limitations of crash avoidance technologies?

    For systems requiring drivers to take action, their effectiveness depends on whether drivers use the technologies, understand the information from the system and respond appropriately. Interpreting warnings from multiple systems may be confusing or even distracting for some drivers. Driver incapacitation presents a serious challenge for unintentional, frequently severe lane departure crashes. Cicchino, J.B. & Zuby, D.S. 2017. Prevalence of driver physical factors leading to unintentional lane departure crashes. Traffic Injury Prevention 18(5): 481-487.

    In addition to driver challenges, the technology itself can have limitations. For example, lane departure warning systems use sensors to register lane markings or the road edge, which may be problematic on roads that aren't well marked or are covered with snow. Sensors such as cameras, radar and LIDAR also may not function well in low light or inclement weather. Some systems only work at certain speeds.

  8. What new technologies can we expect in the future?

    The landscape of in-vehicle technologies is rapidly changing as new features continue to be introduced. Advances also are being made in intelligent transportation systems that allow vehicles to communicate with one another or with the roadway infrastructure.

    Vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications, collectively known as connected vehicle technology, are prototype safety systems in which vehicles and roadway infrastructure communicate over a wireless network.

    With V2V communication, vehicles transmit information regarding their actions to other vehicles. For example, in a long chain of vehicles, if the lead vehicle suddenly brakes, this information will be transmitted to every other vehicle in the chain so that the other drivers are alerted. It also could be possible for the trailing vehicles to automatically begin braking when the lead vehicle's signal is received.

    With V2I communication, cars receive and transmit information to roadway infrastructure. For example, highway systems could monitor vehicle location within a lane. If the vehicle is detected drifting out of a lane, the system could alert the vehicle. In urban environments, traffic signals can alert vehicles of an impending light change so drivers can prepare to stop.

    A 2013 pilot study in Ann Arbor, Mich., tested the functionality and reliability of these connected vehicle technologies. Research and Innovative Technology Administration. 2012. Connected vehicle research. Available at http://www.its.dot.gov/connected_vehicle/connected_vehicle.htm. Accessed: June 20, 2012. The results indicate connected vehicle technologies are technically feasible and would reduce property-damage and injury crashes. However, there are some barriers to wide adoption, including privacy and security concerns, as well as technical aspects and performance requirements of the systems. Harding, J.; Powell, G.; Yoon, R.; Fikentscher, J.; Doyle, C.; Sade, D.; Lukuc, M.; Simons, J.; and Wang, J. 2014. Vehicle-to-vehicle communications: readiness of V2V technology for application. Report no. DOT HS-812-014. Washington, DC: National Highway Traffic Safety Administration.

    The U.S. Department of Transportation is funding additional pilot deployment sites to refine system and operational requirements and inform a comprehensive deployment plan. United States Department of Transportation. Connected vehicles CV Pilot Deployment Program. Available at: http://www.its.dot.gov/pilots/index.htm. Accessed February 26, 2016. In January 2017, NHTSA issued a notice of proposed rulemaking that will require passenger vehicles to have the technology by 2023 and is considering comments received from the public before finalizing the rule.  Office of the Federal Register. 2017. National Highway Traffic Safety Administration –notice of proposed rulemaking. Docket no. NHTSA-2016-0126; 49 CFR Part 571 Federal Motor Vehicle Safety Standards: Vehicle-to-Vehicle (V2V) Communications. Washington, DC: National Archives and Records Administration.

    NHTSA estimates that two V2V functions, intersection movement assist ant left turn assist, together could potentially prevent up to nearly 600,000 crashes and about 1,300 fatalities annually when fully deployed through the light vehicle fleet. Office of the Federal Register. 2017. National Highway Traffic Safety Administration –notice of proposed rulemaking. Docket no. NHTSA-2016-0126; 49 CFR Part 571 Federal Motor Vehicle Safety Standards: Vehicle-to-Vehicle (V2V) Communications. Washington, DC: National Archives and Records Administration. These functions warn drivers when they are at risk of crashing with another vehicle when entering or turning left at an intersection.

July 2017

  1. What is electronic stability control (ESC)?

    ESC is a vehicle control system comprised of sensors and a microcomputer that continuously monitors how well a vehicle responds to a driver's steering input, selectively applies the vehicle brakes, and modulates engine power to keep the vehicle traveling along the path indicated by the steering wheel position. This technology helps prevent the sideways skidding and loss of control that can lead to rollovers. It can help drivers maintain control during emergency maneuvers when their vehicles otherwise might spin out, or reduce vehicle speed to prevent running off the outside of a curve. The systems have been marketed under various names, including dynamic stability control, vehicle stability control and dynamic stability and traction control, among others.

  2. How does ESC help drivers maintain control?

    A driver loses control when the vehicle goes in a direction different from the one the steering wheel position indicates. This typically occurs when a driver tries to turn very hard or turn on a slippery road. Then the vehicle may understeer or oversteer. When it oversteers it turns more than the driver intended because the rear end is spinning or sliding out. When a vehicle understeers it turns less than the driver intended and continues in a forward direction because the front wheels have insufficient traction. ESC can prevent under- and oversteer by selectively braking wheels to produce a counteracting force which helps correct the vehicle's direction of travel. In some cases engine throttle also is reduced.

    How ESC works
  3. How effective is ESC in preventing crashes?

    In Institute studies, ESC has been found to reduce fatal single-vehicle crash risk by 49 percent and fatal multiple-vehicle crash risk by 20 percent for cars and SUVs. Many single-vehicle crashes involve rolling over, and ESC effectiveness in preventing rollovers is even more dramatic. It reduces the risk of fatal single-vehicle rollovers by 75 percent for SUVs and by 72 percent for cars. Farmer, C.M. 2010. Effects of electronic stability control on fatal crash risk. Arlington, VA: Insurance Institute for Highway Safety. Federal studies also show large benefits. The National Highway Traffic Safety Administration (NHTSA) estimates the installation of ESC reduces single-vehicle crashes of cars by 32 percent and single-vehicle crashes of SUVs by 57 percent. NHTSA estimates that ESC has the potential to prevent 72 percent of the car rollovers and 64 percent of the SUV rollovers that would otherwise occur in single-vehicle crashes. Sivinski, R. 2011. Crash prevention effectiveness of light-vehicle electronic stability control: an update of the 2007 NHTSA evaluation. Report no. DOT HS-811-486. Washington, DC: U.S. Department of Transportation.  

    ESC also has great potential to prevent rollover crashes of large trucks. NHTSA estimates that ESC on large trucks could prevent 40 to 56 percent of rollovers and 14 percent of loss-of-control crashes. Wang, J.S. 2011. Effectiveness of stability control systems for truck tractors. Report no. DOT HS-811-437. Washington, DC: Department of Transportation.

  4. Does ESC activate in typical everyday driving?

    For most drivers ESC isn't likely to activate frequently. It won't prevent most of the fender-bender crashes that occur so often in stop-and-go traffic, for example. It's designed to help a driver in the relatively rare event of loss of control at high speed or on a slippery road.

  5. Does the government require ESC?

    As of the 2012 model year, the federal government requires ESC in all cars, SUVs, pickups and minivans. Office of the Federal Register. 2007. National Highway Traffic Safety Administration – Final rule. Docket no. NHTSA-2007-27662; 49 CFR Parts 571 and 585 – Federal Motor Vehicle Safety Standards, Electronic stability control systems, Controls and displays. Federal Register, vol. 72, no. 66, pp. 17236-322. Washington, DC: National Archives and Records Administration. A similar requirement for truck tractors was finalized in 2015. Office of the Federal Register. 2015. National Highway Traffic Safety Administration – Final rule. Docket no. NHTSA-2015-0056; 49 CFR Part 571 – Federal Motor Vehicle Safety Standards, Electronic stability control systems for heavy vehicles. Federal Register, vol. 80, no. 120, pp. 36049-36110. Washington, DC: National Archives and Records Administration. Most new truck tractors will be required to have ESC as of Aug. 1, 2017. The remaining types have until 2019.

  6. How long has ESC been available?

    ESC was introduced in 1995 as optional equipment on luxury cars. By the 2001 model year it was standard on a number of high-selling vehicles and available as an option on many more.

    NHTSA phased in its ESC rule, requiring the technology on 55 percent of model year 2009 vehicles and increasing the percentage each year until model year 2012, when manufacturers had to equip all their passenger vehicles with ESC. Office of the Federal Register. 2007. National Highway Traffic Safety Administration – Final rule. Docket no. NHTSA-2007-27662; 49 CFR Parts 571 and 585 – Federal Motor Vehicle Safety Standards, Electronic stability control systems, Controls and displays. Federal Register, vol. 72, no. 66, pp. 17236-322. Washington, DC: National Archives and Records Administration. Prior to 2012, the Institute required vehicles to have ESC in order to qualify for a TOP SAFETY PICK award.

  7. Can ESC help reduce insurance losses?

    Yes. Losses under collision coverage are about 15 percent lower for vehicles with ESC than for predecessor models without it, according to an analysis by HLDI. Highway Loss Data Institute. 2006. Electronic stability control. HLDI Bulletin 23(1). Arlington, VA. ESC doesn't have much effect on liability claims filed when an at-fault driver damages someone else's car or property or the frequency of personal injury claims filed to cover medical expenses.

July 2017

  1. What are antilock brakes?

    Antilock brakes are designed to help drivers avoid crashes. Without antilocks, hard braking can cause wheels to lock, sending a vehicle into a skid. Wheel lockup can result in longer stopping distances, loss of steering control and, when road friction is uneven, loss of stability if the vehicle begins to spin.

    The main benefit of an antilock braking system (ABS) is that it can reduce these problems on wet and slippery roads. ABS works with a vehicle's normal service brakes to decrease stopping distance and increase the control and stability of the vehicle during hard braking.

    The principle behind ABS is that a skidding wheel provides less stopping force and control than a wheel that is rotating. Antilocks prevent wheels from skidding by monitoring the speed of each wheel and automatically pulsing the brake pressure on any wheels where skidding is detected. ABS doesn't make much difference in stopping distances on dry roads, although it can enhance vehicle stability and allow the driver to maintain steering control during an emergency stop, when conventional brakes might allow wheel lockup and skidding.

  2. How does ABS work?

    ABS differs among vehicles, but there are some basic similarities. Each system has sensors that monitor the rotational speeds of selected wheels when brakes are applied. When one of these wheels approaches lockup, a control unit reduces brake pressure to that wheel or set of wheels just enough to allow rotation again. This typically happens many times per second, resulting in improved control and, on many wet and slippery surfaces, shorter stopping distances.

    Most passenger vehicles have four-wheel systems with wheel-speed sensors on each wheel. In one type of system, ABS reduces brake pressure to both rear wheels whenever one approaches lockup. Brake pressure to the front wheels of four-wheel systems is controlled independently to maximize stopping power, which is concentrated in the front. In four-wheel independent systems, each wheel is controlled individually, so when any one approaches lockup, brake pressure is reduced to that wheel.

    Some pickups and cargo vans have rear-wheel-only antilock systems to address different braking needs when vehicles are loaded versus unloaded. ABS monitors the rotational speeds of rear wheels only and releases pressure to both when either is about to lock.

    Tractor-trailers have separate antilock systems for the tractors and the trailers. Ideally, both the tractor and trailer of a combination rig should have antilock brakes, but putting antilocks on either component should produce improvement compared with conventional brakes. With antilocks on the tractor only, a driver can maintain better steering control even if trailer wheels lock and the trailer swings. If only the trailer has ABS, trailer swing can be reduced even if steering control is lost.

    ABS is particularly important on motorcycles because locking a wheel during hard braking, especially the front wheel, often results in a serious fall. Motorcycle ABS systems operate on both front and rear wheels. They typically involve separate controls for each wheel, although ABS may be included in systems that link the operation of both brakes.

  3. Why doesn't ABS reduce stopping distances as much on dry roads as wet ones?

    Adequate braking is easy to achieve on dry roads with or without antilock brakes. Even if wheels lock, the coefficient of friction between tires and road surface still is relatively high, so a vehicle stops relatively quickly.

  4. Has ABS on passenger vehicles reduced crashes?

    Although antilocks perform well on the test track, there is little evidence that they have substantially reduced real-world crashes. A 1994 Highway Loss Data Institute (HLDI) study Highway Loss Data Institute. 1994. Collision and property damage liability losses of passenger cars with and without antilock brakes. Insurance special report A-41. Arlington, VA. and a subsequent 1995 study Highway Loss Data Institute. 1995. Three years' on-the-road experience with antilock brakes: an update. Insurance special report A-47. Arlington, VA. compared insurance claims for groups of otherwise identical cars with and without antilocks, finding no differences in the frequency or cost of crashes for which insurance claims for vehicle damage were filed. Because ABS should make the most difference on wet and slippery roads, researchers also studied the insurance claims experience in 29 states during winter months. Even here they found no difference in claim frequency for vehicles with and without antilock brakes. A 1997 Institute study Farmer, C.M.; Lund, A.K.; Trempel, R.E.; and Braver, E.R. 1997. Fatal crashes of passenger vehicles before and after adding antilock braking systems. Accident Analysis and Prevention 29(6):745-57. and a 2001 update Farmer, C.M. 2001. New evidence concerning fatal crashes of passenger vehicles before and after adding antilock braking systems. Accident Analysis and Prevention 33(3):361-9. reported no difference in the overall fatal crash involvement of cars with and without antilocks.

    According to one federal report, "the overall, net effect of antilock brakes" on both police-reported crashes and fatal crashes "was close to zero." Kahane, C.J. 1994. Preliminary evaluation of the effectiveness of antilock brake systems for passenger cars. Report no. DOT HS-808-206. Washington, DC: National Highway Traffic Safety Administration. A more recent federal report concluded that ABS reduces overall crash involvement risk by 6 percent for cars and 8 percent for pickups and SUVs but has no effect on fatal crash risk. Kahane, C.J. and Dang, J.N. 2009. The long-term effect of ABS for passenger cars and LTVs. Report no. DOT HS-811-182. Washington, DC: National Highway Traffic Safety Administration. Other researchers have found that antilock-equipped cars are less likely to rear-end other vehicles but more likely to have other vehicles rear-end them. Evans, L. and Gerrish, P. 1996. Antilock brakes and risk of front and rear impact in two-vehicle crashes. Accident Analysis and Prevention 28(3):315-23. The net result is little effect on overall crash risk. Still another analysis found a net benefit of antilocks on nonfatal crashes but no effect on fatal crashes. Padmanaban, J. and Lau, E. 1996. Accident experience of passenger vehicles with four-wheel antilock braking systems. Proceedings of the 40th Annual Conference of the Association for the Advancement of Automotive Medicine, 111-25. Des Plaines, IL: Association for the Advancement of Automotive Medicine.

  5. Why hasn't passenger vehicle ABS reduced crashes as expected?

    No one knows for sure why ABS test performance has not translated into a substantial reduction in real-world crashes. A possible reason is that the average motorist rarely experiences total loss of vehicle control, which antilocks are designed to prevent. There also is evidence that many drivers in the early days of antilock brakes did not know how to use them effectively. A 1994 Institute survey of drivers with antilock-equipped cars found that more than 50 percent in North Carolina and 40 percent in Wisconsin incorrectly thought they should pump the brakes. Williams, A.F. and Wells, J.K. 1994. Driver experience with antilock brake systems. Accident Analysis and Prevention 26(6):807-11.

  6. Is motorcycle ABS effective at reducing crashes?

    Yes. Results from recent studies by IIHS and HLDI compared crash rates for motorcycles equipped with optional ABS against the same models without the option. The rate of fatal crashes per 10,000 registered vehicle years was 31 percent lower for motorcycles equipped with optional ABS than for those same motorcycles without ABS. Teoh, E.R. 2013. Effects of antilock braking systems on motorcycle fatal crash rates: an update. Insurance Institute for Highway Safety. Arlington, VA.  In crashes of all severities, the frequency at which insurance collision claims were filed was 20 percent lower for the ABS models. Highway Loss Data Institute. 2013. Evaluation of motorcycle antilock braking systems alone and in conjunction with combined control braking systems. HLDI Bulletin 30(10). Based on these findings, IIHS and HLDI have petitioned the National Highway Traffic Safety Administration to require manufacturers to equip all new motorcycles with this technology.

  7. How long have antilock brakes been around? Are they widely available?

    The idea of antilock brakes has been around for years. They first were used on airplanes in the 1950s. A rear-wheel system was developed for the 1969 Ford Thunderbird, and the 1971 Chrysler Imperial had four-wheel antilocks.

    Modern antilocks were first introduced on 1985 models. By the 1987 model year, they were standard or optional on about 30 domestic and foreign car models. Availability soared to 90 models the next year.

    ABS is a component of electronic stability control (ESC). Thus, the federal requirement for ESC has made antilock brakes standard equipment on all passenger vehicles as of the 2012 model year.

  8. Is ABS required on big truck rigs?

    In March 1995, the National Highway Traffic Safety Administration issued a rule requiring antilock brakes for heavy trucks, tractors, trailers and buses. All new truck tractors were required to have antilocks after March 1, 1997, and they were mandatory on new air-braked trailers and single-unit trucks and buses after March 1, 1998. New single-unit trucks and buses with hydraulic brakes had to be equipped with antilocks after March 1, 1999. This was not the first antilock standard for U.S. trucks. A federal brake standard took effect in 1975, but its antilock and stopping distance requirements were suspended after litigation in 1978.

    ABS is important for big trucks because of the poor braking capabilities of these vehicles compared with passenger cars. On dry roads, stopping distances for big trucks are much longer than those of passenger cars — 47 percent longer in Institute tests. Insurance Institute for Highway Safety. 1990. Special issue: Antilock brakes for trucks. Status Report 25(5):1-7. On wet and slippery roads, the stopping distance disparity is even worse. Tractor-trailer combinations also have the potential for loss of control and jackknifing, especially on slippery roads. (Jackknifing occurs when the rear wheels of a tractor lock up, allowing the tractor to skid and spin so that it folds into the trailer. This also can happen when trailer wheels lock and cause the trailer to swing around the tractor.) Antilock brakes not only reduce stopping distances on wet and slippery roads, but also help drivers maintain control.

    The standard for tractors requires antilock control on the front axle and at least one rear axle. On at least one of the tractor axles, each wheel must be independently controlled by an antilock modulator. This ensures that a wheel provides shorter stopping distances and optimal braking force on all surfaces, especially on roads where one side is slipperier than the other. For semi-trailers, at least one axle must have antilocks. Full trailers must have antilocks for at least one front and one rear axle.

    A 2010 report by the National Highway Traffic Safety Administration concluded that ABS on tractors reduced crash involvement by 3 percent. Allen, K. 2010. The effectiveness of ABS in heavy truck tractors and trailers. Report no. DOT HS-811-339. Washington, DC: National Highway Traffic Safety Administration. However, there was no significant effect on fatal crashes.