A self-driving car is one where software performs the driving task, and the SAE J3016 standard sorts such systems into six levels, from Level 0 to Level 5. Only at Level 4 and above does the system never ask a person to take over within its approved conditions. For driverless taxis, Waymo reports 271.3 million rider-only miles through June 2026 and a serious-injury-or-worse crash rate of 0.01 per million miles, against 0.21 for a human-driver benchmark, but the company produced these figures itself and states their limits.
Key takeaways
- Levels 0 to 2 keep the human responsible for driving and supervision; Level 3 hands driving to the system but requires a person to take over when it asks.
- A car whose features only assist, such as adaptive cruise control with lane centering, is not self-driving in the SAE sense.
- Waymo's published crash rates are far below its benchmark, but the data cover surface streets in a handful of cities and exclude snow.
- Fault is not assessed in Waymo's comparison, and fatalities are not reported separately because mileage is still too low for statistical significance.
- In the United States, a federal order requires crash reports from automated driving systems; in Canada, Transport Canada publishes testing guidelines and a safety framework.
The six levels, and who is driving
SAE International's J3016 taxonomy, jointly revised with ISO in 2021, divides driving automation by who performs the driving task and who is the fallback. Levels 0 to 2 are called driver support systems, and Levels 3 to 5 are automated driving systems. The wording below follows SAE's public chart.
| Level | Name | Who drives | Typical example |
|---|---|---|---|
| 0 | No driving automation | Human; system gives warnings and momentary help | Automatic emergency braking, blind spot warning |
| 1 | Driver assistance | Human, supervising steering or speed support | Adaptive cruise control or lane centering |
| 2 | Partial automation | Human, constantly supervising both | Lane centering with adaptive cruise control |
| 3 | Conditional automation | System, under limited conditions; person must drive when the feature requests | Traffic jam chauffeur |
| 4 | High automation | System; no takeover request within its conditions | Local driverless taxi |
| 5 | Full automation | System, under all conditions | Not shown in the sources cited here |
The practical line sits between Levels 2 and 3. With a Level 2 feature engaged, the person is driving in the legal and technical sense. Driverless taxis are generally classed as Level 4, because they operate only inside defined service areas.
What Waymo reports
Waymo publishes a safety impact hub with data through June 2026. The company says it has driven 271.3 million rider-only miles, meaning no human driver on board. The hub compares Waymo's crash rates with a benchmark built from state police-reported crashes and vehicle miles in Phoenix, San Francisco, Los Angeles, and Austin. Rates are incidents per million miles.
| Outcome | Waymo | Benchmark | Difference |
|---|---|---|---|
| Serious injury or worse | 0.01 | 0.21 | 94.82 percent lower |
| Any injury reported | 0.67 | 3.77 | 82.12 percent lower |
| Airbag deployment, any vehicle | 0.29 | 1.61 | 81.68 percent lower |
For pedestrians, the hub counts seven injury crashes against 93 expected from the benchmark, which Waymo describes as 93 percent fewer.
Why the numbers do not settle the debate
Waymo lists its own caveats, and they matter. The benchmark covers passenger vehicles on surface streets only, so freeway driving is excluded. Snowfall is absent from both datasets. Waymo's crash counts come from federal reports with a lower reporting threshold than police data, and the any-injury benchmark includes a 32 percent underreporting correction while the serious-injury benchmark has none. Fault is not assessed, so every crash counts regardless of who caused it. Fatalities are not reported separately because mileage is not yet large enough for a statistically meaningful comparison. The page also says the results are retrospective and do not by themselves establish that driving is "safe enough."
The data describe one operator in a few warm-weather cities. They say little about a different company, a snowy road, or a highway.
Oversight in the United States and Canada
In the United States, the National Highway Traffic Safety Administration (NHTSA) runs a Standing General Order that requires identified manufacturers and operators to report certain crashes involving automated driving systems or Level 2 driver assistance. A crash is reportable when the system was engaged at any time within 30 seconds before it. The order has been amended in 2021, 2023, and 2025. Waymo's hub draws on these reports.
In Canada, Transport Canada's page on connected and automated vehicles, last modified February 10, 2025, lists its guidelines for testing automated driving systems in Canada (Version 2.0), a safety framework for connected and automated vehicles (2.0), and a safety assessment for automated driving systems. The page does not describe the contents of those documents, so readers should consult each one directly.
How to read a self-driving safety claim
- Which SAE level is the system, and does a person have to supervise or take over?
- Where and in what weather was the data collected?
- Is the comparison group matched on road type, city, and crash reporting?
- Does the claim cover injury crashes, fatalities, or all contact events?
- Who produced the analysis, and was it independently reviewed?
This article offers general information about technology and regulation. It is not safety, legal, or travel advice, and it does not recommend a product or service.
FAQ
Is a car with adaptive cruise control and lane centering self-driving?
No. That combination is Level 2 partial automation, and the person behind the wheel remains responsible for supervising the car at all times.
What is the difference between Level 3 and Level 4?
At Level 3 the system drives under limited conditions but may ask a person to take over, and the person must do so. At Level 4 the system does not require a takeover within its approved conditions, which is why a driverless taxi service is described as Level 4.
Are robotaxis safer than human drivers?
Waymo's published data show much lower injury-crash rates than its benchmark, but the data are company-reported, cover specific cities and surface streets, and do not assess fault. The evidence is promising for that service and not a general verdict on all automated driving.
Are fully self-driving cars sold to the public?
Level 5 would drive everywhere in all conditions, and the sources cited here describe no such product. Driverless taxis operate at Level 4 in limited service areas, and the SAE chart lists features such as adaptive cruise control and lane centering as support features that leave the person responsible.
Related reading
- Main topics and applications of AI
- Well-known AI systems
- Software robots versus AI in business processes
- What AI is and where it is used
More in AI Basics.
Last verified: October 2026
Sources
- SAE J3016, Taxonomy and Definitions for Terms Related to Driving Automation Systems for On-Road Motor Vehicles, SAE International and ISO, 2021 (levels as shown in the public SAE chart)
- Safety Impact, Waymo, data through June 2026
- Standing General Order on Crash Reporting, National Highway Traffic Safety Administration, amended 2025
- Connected and automated vehicles, Transport Canada, page modified February 10, 2025