Japan's Approach to Level 4 Certification

Honda's Legend sedan holds a specific distinction: it was among the first production vehicles anywhere to receive a Level 3 type certification, following Japan's amendment of its Road Traffic Act to permit that class of automated driving. Getting there required Japan to formally define what a Level 3 system was allowed to do behind the wheel, and what obligations shifted from driver to vehicle once the system engaged, well before most markets had settled the question.

Certifying a production sedan for Level 3 is a narrower problem than certifying an entire service. It focuses on one vehicle model behaving correctly across the ordinary range of conditions a private car encounters day to day. A designated bus route, by contrast, is a fixed corridor with known geometry and known traffic patterns that doesn't change from one week to the next. That predictability is what makes route-specific Level 4 approval tractable in a way that opening an entire road network to any qualifying vehicle simply is not.

Japan's move to Level 4 did not follow the same script. Rather than writing a single national law authorising driverless operation everywhere, as Germany later did, regulators approved specific services in specific places: designated automated bus routes running fixed corridors, cleared for driverless operation under conditions attached to that route rather than to the country as a whole. A service approved on one route does not automatically clear a different one.

Getting a route approved this way is not a single sign-off. Japan's framework for driverless mobility services requires clearance from more than one authority before a route can run without an onboard driver: traffic-law approval covering how the vehicle behaves on the road, and a separate vehicle-safety approval covering the vehicle itself, echoing the split between traffic-law and vehicle-engineering regulation that shows up in other markets as well. A service operator has to satisfy both tracks for a given corridor before it can start running, which is part of why each new route tends to take real time to bring online even after the underlying legal framework already exists. A route that clears traffic-law approval quickly can still sit unopened for a stretch afterward if the parallel vehicle-safety sign-off hasn't caught up, which is part of why the pace of route expansion has looked slower than the headline legal change might have suggested it would be.

Most of these approved routes also carry a remote-monitoring condition attached to the permit itself: a human operator watches the vehicle's status from off-vehicle and can intervene or halt the service if something goes wrong, even though no one is riding along to do the same job from inside the cabin. That condition doesn't undercut the driverless label, the vehicle is still operating without an onboard driver, but it does mean “driverless” in this context describes where the human sits, not whether a human is involved in the loop at all. It also means a service's staffing costs shift rather than disappear entirely once a route goes driverless, since monitoring several vehicles remotely from one control point is a different cost structure than paying a dedicated safety driver to ride along in each vehicle individually.

That trade-off is real. It is more centralized than the fully permit-based system used across US states, where each state runs its own process independent of the others, but it is also narrower than a blanket national statute covering any qualifying use case. Whether that middle path proves more durable than either extreme, easier to expand route by route without needing new legislation each time, is one of the more interesting open questions in AV regulation right now.

None of this required Japan to redefine what "Level 3" or "Level 4" mean in the first place; those definitions come from the SAE's own taxonomy, which Japan adopted rather than rewrote.