Advanced Driver Assistance Systems and Automated Driving Systems

Since the first fatal crash, in 2016 in Williston, Florida involving a vehicle with driving automation features engaged, the NTSB has investigated many crashes involving vehicles equipped with various driving automation features. Modern vehicles use many technologies to support the driving task, and their capabilities have become increasingly sophisticated. These advanced driver assistance systems (ADAS) can be limited to providing warnings (such as blind spot warnings) and momentary assistance (such as automatic emergency braking). Some systems provide steering support to the driver (such as lane centering) or brake/acceleration support (such as adaptive cruise control). Other systems offer partial driving automation, providing both steering and brake/acceleration support at the same time. Drivers must constantly supervise the driving environment and driver support features, stay alert, and be ready to take control at any time. The NTSB has also investigated incidents involving vehicles equipped with developmental automated driving systems (ADS) — those that can drive the vehicle under limited conditions— including robotaxi operations tested on public roads.

Our investigations underscore the need for data recording requirements, risk identification and mitigation strategies, and transparent safety evaluations to ensure that various driver assistance and vehicle automated driving systems—whether ADAS or ADS—are deployed safely.

Understanding the Levels of Driving Automation

SAE J3016, defines six levels of driving automation, from Level 0 (no automation) to Level 5 (full automation), and current consumer vehicles are limited to driver assistance and partial automation features—such as adaptive cruise control, lane keeping assistance, and automatic emergency braking—that are designed to support, not replace, an attentive driver.

Safety Issues Across Investigations

Driver Assistance Systems (SAE Level 0-1)

Technologies such as forward collision warning (FCW) and automatic emergency braking (AEB) can detect forward hazards, warn drivers, and, when necessary, automatically brake to prevent or lessen the severity of a crash. The NTSB has issued more than 20 safety recommendations on these systems, urged that they be installed as standard equipment, and advocated for their inclusion and performance ratings in the US New Car Assessment Program. Intelligent speed assistance (ISA) helps drivers avoid excessive speeds by comparing a vehicle’s location and speed against posted speed limits and providing warnings—or, in some designs, actively limiting acceleration—when the vehicle exceeds the speed limit. The NTSB has investigated multiple speeding-related crashes, including a multivehicle collision in North Las Vegas, Nevada, that led to new recommendations to require ISA in all new vehicles and to encourage vehicle manufacturers to implement ISA as standard equipment. The NTSB studied speeding-related crashes in a 2017 Safety Study, which examined causes of and trends in speeding-related passenger vehicle crashes and countermeasures to prevent these crashes (such as ISA).

Partial Driving Automation (SAE Level 2)

Our investigations revealed several recurring issues, each critical to safe operation of the vehicle or postcrash analysis. We determined the following: <ul><li>Partial automation systems have considerable limitations in detecting hazards, as well as in maintaining the appropriate travel path. </li><li>Lack of federal guidance for SAE Level 2 systems in passenger vehicles has led to safety-critical gaps in: (1) mitigating known system limitations, (2) enhancing safety redundancy by ensuring concurrent engagement of safety technologies, and (3) promoting driver engagement by design.</li><li>Since drivers can become disengaged from the driving task for an extended period, an effective method of monitoring and maintaining driver engagement is essential.  </li><li>There is an urgent need for standardized US-based driver monitoring system performance requirements, including the ability to detect accumulated short distractions, differentiate true on-road glances from glances to devices in the forward line of sight, and issue timely multimodal alerts.</li><li>When automakers lack a mechanism to become informed about incidents involving their vehicles that meet the reporting criteria specified in the National Highway Traffic Safety Administration's (NHTSA) SAE International Level 2 (L2) Standing General Order (SGO)—as was the case for Ford in the San Antonio and Philadelphia crashes—the completeness of L2 SGO incident data cannot be assured, and the automakers’ ability to investigate these incidents and the safety risks associated with L2 systems are likely to be limited.</li><li>Inaction by the US Department of Transportation (US DOT) and NHTSA in establishing requirements for recording automated vehicle control system data—including supporting ADAS features—continues to enable non-standardized and inconsistent data collection, hindering crash investigations and NHTSA’s oversight of potential safety defects associated with SAE Level 2 systems, as well as limiting the broader usefulness of NHTSA’s Level 2 Standing General Order incident database in revealing incidents and crashes involving partial automation.</li></ul>

Automated Driving Systems (SAE Levels 3 to 5)

Our investigations of developmental ADS revealed several issues, each critical to safe operation of the vehicle or postcrash analysis. We determined the following: <ul><li>Testing of developmental automated driving systems exposes their functional limitations, particularly in detecting hazards and predicting the movement of various road users.</li><li>The extent to which these limitations pose a safety risk depends on safety redundancies and risk mitigation strategies implemented during system development and testing.</li><li>Safety drivers/monitors can be affected by automation complacency, which can lead to distraction and failure to monitor the environment and the operation of the automated system.</li><li>There are no federal safety risk management requirements for testing vehicles equipped with automated driving systems on public roads.</li><li>The safety self-assessment reports that some automation developers have submitted to NHTSA have very limited benefit; these reports are voluntary, are not evaluated by NHTSA, and many lack meaningful safety or technical information.</li><li>Due to the lack of federal safety standards or meaningful testing protocols, some states have developed risk-management-focused requirements that developers must meet prior to testing on public roads, whereas many other states lack such requirements.</li><li>When evaluating safety self-assessment reports from entities testing ADS on public roads, safety authorities should evaluate how effectively the entities include school bus operations in their plans. </li><li>Because school buses and the children they carry are an integral part of the transportation system, it is imperative that developers and manufacturers of advanced technologies create systems in which automated and connected vehicles respond appropriately to school buses and their unique operating environment. </li></ul>

Related Technologies

<a href="/advocacy/SafetyIssues/Pages/Connected-Vehicle-Technology-(V2X).aspx">Connected vehicle technologies (V2X)</a> allow vehicles to communicate directly with one another, with roadway infrastructure, and with vulnerable road users, providing warnings and automated responses that can prevent collisions even when hazards are not visible to onboard sensors. The NTSB has long supported nationwide deployment of V2X, recommended that safety regulators and the Federal Communications Commission ensure adequate spectrum and performance standards, and warned that delays in deployment and spectrum reductions undermine the safety potential of automated vehicles.

Related Investigations

Partial Driving Automation Investigations

Automated Driving System Investigations

Key Safety Recommendations

Open Recommendations Representing Critical Safety Priorities

To the US Department of Transportation:

H-26-1: Issue comprehensive guidelines for vehicle manufacturers implementing partial vehicle automation systems that address known system limitations, including:

integration and concurrent engagement of other safety-critical technologies (such as automatic emergency braking, active intelligent speed assistance, and driver monitoring systems);
promoting driver engagement by design;
reducing the safety risks associated with automation complacency and misuse; and
setting maximum operational speeds for automation systems based on overall system capabilities.

To the National Highway Traffic Safety Administration:

H-26-2: Require manufacturers to equip new SAE Level 2-capable passenger vehicles with a telematic system that notifies the manufacturer of crashes meeting your reporting requirements in Standing General Order 2021-01.
H-26-3: Amend 49 Code of Federal Regulations Part 563, “Event Data Recorders,” to require that all new SAE Level 2-capable passenger vehicles record data elements related to these systems, including at a minimum:

system availability;
engagement and activation denial;
driver alerts; and
system faults for automatic emergency braking, forward collision warning, driver monitoring systems, lane departure prevention, lane centering, partial automation system operation, and any other systems deemed necessary.

H-26-4: Require that all new SAE Level 2-capable passenger vehicles be equipped with driver monitoring systems capable of minimizing driver disengagement, automation complacency, and misuse of vehicle automation by, at a minimum: providing warnings about accumulated short glances over a prolonged period of time; differentiating genuine on-road glances from attention directed to objects, such as cell phones, located in the driver’s forward line of sight; and issuing initial and subsequent multimodal alerts at intervals that minimize eyes-off-road duration.
H-20-002: Evaluate Tesla Autopilot-equipped vehicles to determine if the system’s operating limitations, the foreseeability of driver misuse, and the ability to operate the vehicles outside the intended operational design domain pose an unreasonable risk to safety; if safety defects are identified, use applicable enforcement authority to ensure that Tesla Inc. takes corrective action. (Open – Acceptable Response)
H-20-10: When evaluating safety self-assessment reports from entities testing automated driving systems on public roads, evaluate how effectively the entities include school bus operations in their plans. (Open-Unacceptable Response)
H-19-47: Require entities who are testing or who intend to test a developmental automated driving system on public roads to submit a safety self-assessment report to your agency. (Open – Unacceptable Response)
H-19-48: Establish a process for the ongoing evaluation of the safety self-assessment reports as required in Safety Recommendation H-19-47 and determine whether the plans include appropriate safeguards for testing a developmental automated driving system on public roads, including adequate monitoring of vehicle operator engagement, if applicable. (Open – Unacceptable Response)
H-17-38: Develop a method to verify that manufacturers of vehicles equipped with Level 2 vehicle automation systems incorporate system safeguards that limit the use of automated vehicle control systems to those conditions for which they were designed.

To the States:

H-19-49: To the State of Arizona: Require developers to submit an application for testing ADS-equipped vehicles that, at a minimum, details a plan to manage the risk associated with crashes and operator inattentiveness and establishes countermeasures to prevent crashes or mitigate crash severity within the ADS testing parameters. (Open – Await Response)
H-19-50: To the State of Arizona: Establish a task group of experts to evaluate applications for testing vehicles equipped with automated driving systems, as described in Safety Recommendation H-19-49, before granting a testing permit. (Open – Await Response)

To Vehicle Manufacturers:

H-26-5: To the Ford Motor Company: Revise the driver monitoring systems (DMS) in your new vehicles to detect and provide warnings about accumulated short distractions over a prolonged period of time; differentiate genuine driver on-road glances from attention directed to objects, such as cell phones, located in the driver’s forward line of sight; and issue initial and subsequent multimodal alerts at intervals that minimize eyes-off-road duration.
H-26-6: To the Ford Motor Company: Modify your BlueCruise system for new vehicles to require that the automatic emergency braking system is engaged and that the Intelligent Adaptive Cruise Control system uses appropriate speed tolerances to mitigate excessive speeding, taking into consideration the system’s operational capabilities as well as traffic and highway complexity.
H-17-41: To the manufacturers of vehicles equipped with Level 2 vehicle automation systems (Volkswagen Group of America, BMW of North America, Nissan Group of North America, Mercedes-Benz USA, Tesla Inc., and Volvo Group North America): Incorporate system safeguards that limit the use of automated vehicle control systems to those conditions for which they were designed. (Open – Acceptable Action)
H-17-42: To the manufacturers of vehicles equipped with Level 2 vehicle automation systems (Volkswagen Group of America, BMW of North America, Nissan Group of North America, Mercedes-Benz USA, Tesla Inc., and Volvo Group North America): Develop applications to more effectively sense the driver’s level of engagement and alert the driver when engagement is lacking while automated vehicle control systems are in use. (Open – Acceptable Response)

Updated April 21, 2026