Highways is this weird thing where building the L2/L3 capability is comparatively easy (Which is why Tesla autopilot has been halfway decent for a long time now

Highways is this weird thing where building the L2/L3 capability is comparatively easy (Which is why Tesla autopilot has been halfway decent for a long time now, and BMW have a true L3 system in restricted areas where you can take eyes off the road), but L4 is really hard because a true L4 system has to always be safe even if the driver doesn't take over. You could be tens of miles between highway exits, and just stopping on a highway isn't exactly safe by default. An L4 system therefore needs to handle anything between its current position and the next exit which massively ramps up the number of possible situations it needs to be able to handle compared to the L2/L3 equivalent. L4 in an urban environment is weirdly feasible by comparison, even though we still don't have examples of extremely good L2/L3 systems yet (there's far more complexity by default compared to highways: lights, pedestrians, complex lane decisions, more visual noise, higher average relative speeds) we already have these L4 Taxis being rolled out. The reason is that if a driver doesn't take over it's much easier to find a "safe" place to stop. Apart from getting stuck in the middle of a junction, you can feasibly park up anywhere that has speeds <=40mph.