This National Highway Traffic Safety administration document:
• Provides a description of developments in automated driving and explains the levels of automation defined by NHTSA.
• Provides an overview of NHTSA’s automated research program.
• Provides recommended principles that States may wish to apply as part of their considerations for driverless vehicle operation, especially with respect to testing and licensing.
NHTSA intends to regularly review and update this document as necessary to provide additional clarity, reflect new findings, and outline any regulatory activity that the agency may pursue with respect to automated vehicles. As discussed above, we look forward to working with stakeholders on these issues.
Recently, research activities by several companies to develop “autonomous” (self-driving) vehicles that can perform certain driving functions automatically have captured the nation’s attention. Several states have acted to encourage development of self-driving vehicles by enacting legislation that expressly permits their operation under certain conditions and a significant number of additional states are considering similar legislation.
At the same time, vehicle manufacturers have begun to offer or announced plans to offer in the next several model years certain types of automated crash avoidance safety systems as features on new vehicles. NHTSA has been actively involved in researching these advanced technologies, which rely on in-vehicle sensors and cameras to obtain safety-critical data.
For example, NHTSA is engaged in research to evaluate the effectiveness of currently available automated braking systems in avoiding or mitigating crashes. As part of this research, the agency is developing test procedures to evaluate the technologies and methods to assess their safety benefits.
Also, NHTSA and other Department of Transportation agencies, in conjunction with the auto industry, have been conducting in-depth research and demonstration of vehicle-to-vehicle (V2V) communications technology, which offers substantial crash avoidance possibilities, particularly when linked to active in-vehicle crash avoidance systems.
Accordingly, three distinct but related streams of technological change and development are occurring simultaneously:
(1) in-vehicle crash avoidance systems that provide warnings and/or limited automated control of safety functions;
(2) V2V communications that support various crash avoidance applications; and
(3) self-driving vehicles.
Automated vehicles are those in which at least some aspects of a safety-critical control function (e.g., steering, throttle, or braking) occur without direct driver input. Vehicles that provide safety warnings to drivers (forward crash warning, for example) but do not perform a control function are, in this context, not considered automated, even though the technology necessary to provide that warning involves varying degrees of automation (e.g., the necessary data are received and processed, and the warning is given, without driver input). Automated vehicles may use onboard sensors, cameras, GPS, and telecommunications to obtain information in order to make their own judgments regarding safety-critical situations and act appropriately by effectuating control at some level. Accordingly, for purposes of this discussion, vehicles equipped with V2V technology that provide only safety warnings are not automated vehicles, even though such
warnings by themselves can have significant safety benefits and can provide very valuable.
• Level 0 – No-Automation. The driver is in complete and sole control of the primary vehicle controls (brake, steering, throttle, and motive power) at all times, and is solely responsible for monitoring the roadway and for safe operation of all vehicle controls. Vehicles that have certain driver support/convenience systems but do not have control authority over steering, braking, or throttle would still be considered “level 0” vehicles. Examples include systems that provide only warnings (e.g., forward collision warning, lane departure warning, blind spot monitoring) as well as systems providing automated secondary controls such as wipers, headlights, turn signals, hazard lights, etc. Although a vehicle with V2V warning technology alone would be at this level, that technology could significantly augment, and could be necessary to fully implement, many of the technologies described below, and is capable of providing warnings in several scenarios where sensors and cameras cannot (e.g., vehicles approaching each other at intersections).
• Level 1 –Function-specific Automation: Automation at this level involves one or more specific control functions; if multiple functions are automated, they operate independently from each other. The driver has overall control, and is solely responsible for safe operation, but can choose to cede limited authority over a primary control (as in adaptive cruise control), the vehicle can automatically assume limited authority over a primary control (as in electronic stability control), or the automated system can provide added control to aid the driver in certain normal driving or crash-imminent situations(e.g., dynamic brake support in emergencies). The vehicle may have multiple capabilities combining individual driver support and crash avoidance technologies, but does not replace driver vigilance and does not assume driving responsibility from the driver. The vehicle’s automated system may assist or augment the driver in operating one of the primary controls – either steering or braking/throttle controls (but not both). As a result,there is no combination of vehicle controlsystems working in unison that enables the driver to be disengaged from physically operating the vehicle by having his or her hands off the steering wheel AND feet off the pedals at the same time. Examples of function specific automation systems include: cruise control, automatic braking, and lane keeping.
•Level 2 -Combined Function Automation: This level involves automation of at least two primary control functions designed to work in unison to relieve the driver of control of those functions. Vehicles at this level of automation can utilize shared authority when the driver cedes active primary control in certain limited driving situations. The driver is still responsible for monitoring the roadway and safe operation and is expected to be available for control at all times and on short notice. The system can relinquish control with no advance warning and the driver must be ready to control the vehicle safely. An example of combined functions enabling a Level 2 system is adaptive cruise control in combination with lane centering. The major distinction between level 1 and level 2 is that, at level 2 in the specific operating conditions for which the system is designed, an automated operating mode is enabled such that the driver is disengaged from physically operating the vehicle by having his or her hands off the steering wheel AND foot off pedal at the same time.
• Level 3 – Limited Self-Driving Automation: Vehicles at this level of automation enable the driver to cede full control of all safety-critical functions under certain traffic or environmental conditions and in those conditions to rely heavily on the vehicle to monitor for changes in those conditions requiring transition back to driver control. The driver is expected to be available for occasional control, but with sufficiently comfortable transition time. The vehicle is designed to ensure safe operation during the automated driving mode. An example would be an automated or self-driving car that can determine when the system is no longer able to support automation, such as from an oncoming construction area, and then signals to the driver to reengage in the driving task, providing the driver with an appropriate amount of transition time to safely regain manual control. The major distinction between level 2 and level 3 is that at level 3, the vehicle is designed so that the driver is not expected to constantly monitor the roadway while driving.
• Level 4 -Full Self-Driving Automation (Level 4): The vehicle is designed to perform all safety-critical driving functions and monitor roadway conditions for an entire trip. Such a design anticipates that the driver1 will provide destination or navigation input, but is not expected to be available for control at any time during the trip. This includes both occupied and unoccupied vehicles. By design, safe operation rests solely on the automated vehicle system.
NHTSA’s Research Plan for Automated Vehicles
NHTSA has been conducting research on vehicle automation for many years, and this research has already led to regulatory and other policy developments. Our work on electronic stability control (ESC), for example, led us to develop and issue a standard that made that Level 1 technology mandatory on all new light vehicles since MY 2011. More recently, we issued a proposal that would require ESC on heavy vehicles.
The agency has initiated an evaluation of emerging level 2 and level 3 system concepts to answer fundamental human factors questions. The evaluation will examine how drivers react and perform in these types of automated vehicles. In addition, it will consider DVI concepts that may be needed to ensure that drivers safely transition between automated driving and manual operation of the vehicle. The initial research should address the following human factors questions:
• What is the driver performance profile over time in sustained (longer term) and short-cycle (shorter term) automation?
• What are the risks from interrupting the driver’s involvement with secondary tasks when operating a Level 3 type automated vehicle?
• What are the most effective hand-off strategies between the system and the driver including response to faults and failures?
• What are the most effective human-machine interface concepts, guided by human factors best practices, which optimize the safe operation?
The agency is not aware of any systems intended for wide scale deployment currently under development for use in motor vehicles that are capable of Level 4 automation. As we stated previously, very few Level 3 automated systems exist and the systems that do exist are still at the earlier stages of testing/development. Because Level 4 automated systems are not yet in existence and the technical specifications for Level 3 automated systems are still in flux, the agency believes that regulation of the technical performance of automated vehicles is premature at this time. While NHTSA’s authority, expertise, and mandate is to establish uniform, national standards needed for vehicle safety, the agency recognizes that premature regulation can run the risk of putting the brakes on the evolution toward increasingly better vehicle safety technologies.
While the agency does not believe that self-driving vehicles are currently ready to be driven on public roads for purposes other than testing, the agency would like to emphasize that it is encouraged by innovations in automated driving and their potential to transform our roadways.The agency is confident that the development and testing of Level 3 automated systems will provide answers to many of the technical and human factors questions presented by the technology.
NHTSA does not recommend that states authorize the operation of self-driving vehicles for purposes other than testing at this time. We believe there are a number of technological issues as well as human performance issues that must be addressed before self-driving vehicles can be made widely available. Self-driving vehicle technology is not yet at the stage of sophistication or demonstrated safety capability that it should be authorized for use by members of the public for general driving purposes. Should a state nevertheless decide to permit such non-testing operation of self-driving vehicles, at a minimum the state should require that a properly licensed driver(i.e., one licensed to drive self-driving vehicles) be seated in the driver’s seat and be available at all times in order to operate the vehicle in situations in which the automated technology is not able to safely control the vehicle. As innovation in this area continues and the maturity of self-driving technology increases, we will reconsider our present position on this issue.