内容来源：https://www.engadget.com/2240138/if-waymo-cars-are-level-4-automation-what-is-level-5/

内容总结：

Waymo已达L4自动驾驶，距离L5还有多远？

随着无人驾驶出租车空驶穿梭于城市车流，外界常误以为Waymo已实现最高级别的自动驾驶。但从乘客视角看，车内虽无方向盘、无需人工监控或干预，车辆全程自主完成行程，这在实际体验上确实接近“完全自动驾驶”。

然而，按照国际自动机工程师学会（SAE）的自动驾驶分级标准，Waymo目前仍属于L4级，而非最高的L5级。两者核心区别不在于车辆“看起来”有多独立，而在于这种独立运行被允许存在的范围。L4级系统可在限定条件和区域内无需人类输入完成全部驾驶任务，而L5级则彻底取消这些边界。

为何Waymo被归类为L4？

严格来说，被评定为L4的是Waymo的自动驾驶系统“Waymo Driver”。其公开安全研究明确定义其为SAE L4级系统。SAE共设6个级别（L0至L5）：L0需人类完成全部驾驶；L1可连续辅助转向或加速/制动；L2可同时处理转向与加减速，但驾驶员仍须负责；L3系统在特定条件下可全权驾驶，但需人类随时接管；L4则取消了接管要求，系统在预定运行范围内行驶时，车内人员均为乘客而非备用驾驶员。这正是Waymo能宣称“全自动驾驶”却不自称L5的原因——其车辆虽可无人驾驶，但运行仍受明确条件限制。

L4与L5的本质区别：运行设计域（ODD）

这些限制通常被称为“运行设计域”（ODD），即自动驾驶系统被设计运行的地理范围、道路类型及可应对的天气条件等。L4系统在ODD内可独立完成全部驾驶任务，而L5则按美国国家公路交通安全管理局（NHTSA）的描述，需实现“全域运行”，而非局限于特定服务区域。因此，L5并非指车辆在某一操作中“更智能”——Waymo的L4车已能自主完成转向、制动和决策，二者差异在于“适用范围”而非“谁在开车”。Waymo第六代Driver系统扩展了应对极端冬季天气等多元环境的能力，但只要仍受定义边界约束，便始终是L4而非L5。

为何从L4扩展到L5远比扩大L4更艰难？

扩大L4系统时，开发者可明确边界：定义运行区域、需要应对的条件，并据此测试相关场景。而取消边界将令需考虑的情况呈指数级增长。即便在L4阶段，测试已颇具挑战。Waymo在2026年碰撞规避测试研究指出，评估L4系统因潜在危险场景数量庞大而十分复杂，其测试方法需结合人类驾驶数据、自动驾驶测试数据及专家知识。天气因素便是典型例证：2026年5月，Waymo车辆在亚特兰大和圣安东尼奥遭遇积水道路，公司一度暂停或限制部分运营以改进系统。

目前，L5级技术尚无可靠的时间表。NHTSA明确表示，L5技术尚未进入可面向消费者购买的车辆中。SAE分级仅描述技术能力，而非发展路线图。

中文翻译：

如果Waymo汽车属于L4级自动驾驶，要达到L5级还需要什么？

这与其说取决于自动驾驶车辆的能力，不如说取决于它能在什么条件下运行。

看到一辆车在城市的车流中行驶，驾驶座上却空无一人，会让人感觉Waymo似乎已经达到了最高级别的自动驾驶水平。从乘客的角度来看，没有方向盘操作、没有监控、也不需要人工干预，车辆全程自行完成整个行程。

但按照美国汽车工程师学会（SAE）的驾驶自动化分级框架，这种能力仍然属于L4级，而不是最高级别的L5级。关键区别不在于驾驶行为在实践中看起来有多“独立”，而在于这种独立性被允许存在于何种范围内。在L4级，系统可以在无需人工介入的情况下完全独立完成驾驶任务——但仅限于一套明确的条件和地点范围内。L5级则彻底消除了这些边界。

为什么Waymo被视为L4级自动驾驶

严格来说，被归类为L4级的是Waymo Driver——该公司的自动驾驶系统。Waymo发布的 safety 安全研究将其描述为SAE L4级自动驾驶系统，而这一分类也解释了为什么驾驶座空无一人并不自动意味着Waymo达到了L5级。

SAE共定义了六个自动驾驶等级，编号从0到5。美国国家公路交通安全管理局（NHTSA）从L0级开始划分：L0级由人类完成全部驾驶操作，即使安全系统可以短暂介入。L1级可以持续辅助转向或加速/制动，而L2级可以同时处理这两项操作。在这三种情况下，驾驶员仍然对车辆负责。

L3级改变了“谁在开车”这一问题的答案。系统可以在特定条件下完成全部驾驶任务，但当系统提出接管请求时，人类必须随时准备接管。到了L4级，这一要求消失了。一旦自动驾驶系统在其设计运行条件内运行，车内人员就是乘客，而不是后备驾驶员。

这也是为什么Waymo可以将其服务描述为“全自动驾驶”，而不声称达到SAE L5级。它的车辆可以在无人坐在方向盘后的情况下完成出行，但这种能力仍然有明确的运行限制。

L4级与L5级自动化之间的区别

这些限制通常被描述为“运行设计域”（ODD，Operational Design Domain）。简单来说，ODD定义了自动驾驶系统被设计用于在何种地点和何种条件下运行，这可以包括地理范围、适合的道路类型以及能够应对的天气条件。SAE将其定义为自动驾驶系统所设计应对的条件集合，而L4级系统被要求在这些边界内独立完成驾驶任务。

在L4级，系统在其ODD范围内完成全部驾驶任务。L5级则消除了这一限制：NHTSA将其描述为在普遍环境中运行，而非局限于有限的服务区域。所以L5级并不是指车辆在某个特定操作中“更自动驾驶”。一台L4级的Waymo在其运行域内已经在独立完成转向、制动和决策。区别在于范围，而不是由谁负责驾驶。

这就是为什么Waymo可以不断改进其系统，却仍然停留在L4级。例如，Waymo表示其第六代Driver系统扩展了应对更多样化环境的能力，包括极端冬季天气。扩展到新的城市或天气类型使系统能力更强，但只要它仍然在明确的边界内运行，它就仍然是L4级而非L5级。

为什么达到L5级比扩展L4级要困难得多

扩展L4级系统让开发者有了围绕问题的边界。他们可以定义系统应在哪里运行，识别需要应对的条件，并针对与该运行域相关的情景测试系统行为。而移除这些边界则会大大增加需要考量的因素。

这在L4级已经相当困难了。在其2026年关于碰撞规避测试的研究中，Waymo指出，评估L4级系统的复杂性在于可能产生危险状况的操作场景数量极其庞大。其方法论利用人类驾驶数据、Waymo自动驾驶测试数据以及专家知识来识别潜在的危险场景。

天气是这些限制的一个具体例证。2026年5月，Waymo车辆在亚特兰大和圣安东尼奥遭遇了洪水淹没的道路，公司因此在改进期间暂停或限制了部分运营。

目前并没有一个可靠的倒计时来预测L5级何时到来。NHTSA目前表示，L5级技术尚不可供消费者购买的车辆使用，而且SAE等级描述的是能力，而非发展路线图。

英文来源：

If Waymo cars are Level 4 automation, what does it take to be a Level 5?
It's less about an autonomous vehicle's capabilities and more about what conditions it can operate in.
Seeing a car move through city traffic with no one in the driver's seat can make it feel like Waymo has already reached the highest possible level of automation. From a passenger's perspective, there's no steering, no monitoring and no need for a human to intervene. The vehicle handles the entire trip on its own.
But under SAE's (Society of Automotive Engineers) driving automation framework, that capability is still Level 4 rather than the highest: Level 5. The key distinction isn't how "independent" the driving looks in practice, but where that independence is allowed to exist. At Level 4, the system can fully handle the driving task without human input — within a defined set of conditions and locations. Level 5 removes those boundaries entirely.
Why Waymo is considered Level 4 automation
Strictly speaking, it's the Waymo Driver, the company's automated driving system, that's classified as Level 4. Waymo's published safety research describes it as an SAE Level 4 automated driving system, and that classification explains why an empty driver's seat doesn't automatically make a Waymo Level 5.
There are a total of six SAE automation levels, numbered 0 through 5. The National Highway Traffic Safety Administration (NHTSA) starts its breakdown at Level 0, where the human does all the driving even if safety systems can briefly intervene. Level 1 can continuously assist with steering or acceleration and braking, while Level 2 can handle both at the same time. In each case, the driver remains responsible for the car.
Level 3 changes who's doing the driving. The system can handle the entire driving task under certain conditions, but the human must be available to take over when requested. At Level 4, that requirement disappears. Once the automated system is operating within its intended conditions, the occupants are passengers rather than backup drivers.
This is also why Waymo can describe its service as fully autonomous without claiming SAE Level 5. Its cars can complete rides without anyone sitting behind the wheel, but that ability still has defined operating limits.
What separates Level 4 from Level 5 automation
Those limits are usually described as an operational design domain, or ODD. In simple terms, the ODD defines where and under what conditions a self-driving system is designed to operate. That can include geography, the types of roads it's designed for and the weather conditions it can handle. SAE defines it as the set of conditions an automated driving system is designed for, and Level 4 systems are expected to handle driving on their own within those boundaries.
At Level 4, the system handles the entire driving task within its ODD. Level 5 removes that limitation: NHTSA describes it as operating universally rather than within limited service areas. So Level 5 isn't about a car being "more autonomous" during a particular maneuver. A Level 4 Waymo already handles steering, braking and decision-making on its own when operating within its domain. The difference is scope, not who is responsible for driving.
That's why Waymo can keep improving its system and still remain Level 4. For example, Waymo says its sixth-generation Driver has expanded capabilities for more diverse environments, including extreme winter weather. Expanding into new cities or weather types makes the system more capable, but as long as it still operates within defined boundaries, it remains Level 4 rather than Level 5.
Why getting to Level 5 is much harder than expanding Level 4
Expanding a Level 4 system gives developers boundaries around the problem. They can define where the system should operate, identify the conditions it needs to handle and test its behavior against scenarios relevant to that domain. Removing those boundaries dramatically increases what has to be accounted for.
That's already difficult at Level 4. In its 2026 research on collision-avoidance testing, Waymo noted that evaluating a Level 4 system is complicated by the potentially enormous number of operational scenarios in which a hazardous situation might develop. Its methodology identifies potentially hazardous scenarios using human driving data, data from Waymo's automated-driving tests and expert knowledge.
Weather offers a concrete example of those limits. In May 2026, Waymos encountered flooded roads in Atlanta and San Antonio, leading the company to suspend or restrict some operations while it worked on improvements.
There isn't a reliable countdown to when Level 5 will arrive. NHTSA currently says Level 5 technology isn't available in vehicles for consumer purchase, and the SAE levels describe capabilities rather than a development roadmap.