>but why would it affect the database lookup that a self-driving car is doing?
Who said a self driving car is doing a "database lookup"?
If anything, a good self driving car should NOT do any kind of database lookup (of the location of traffic lights etc) and be able to recognize and respond to a moved, impromptu (e.g. because of road work), new, unfamiliar, etc. traffic light.
Getting additional data from a predefined map is expected, even if it's just for something to test the data coming from the sensors. If the car knows there's a traffic light on the map but it isn't 'seeing' one then it should be handing control back to the human, not just carrying on regardless on the assumption that the map is wrong.
A level 5 self-driving car would work completely autonomously without any prior knowledge of the area it's driving in. We're not there yet.
I see -- checked the paper. I knew they were using maps data for the routes and assistance (and that would extend to traffic lights) but I'd expect them to be able to spot all kinds of movable traffic lights (e.g. when there are works or an accident) by pure image recognition/AI.
The standard approach to detecting signal lights is to have a database of GPS positions of the signals, along with rough location in the camera where the signal is expected to occur [1]. Then, when the car nears the signal, it locates the signal and detects the current color.
This mechanism really shouldn't be susceptible to the same biases as humans. The described signal may legitimately be more challenging for the self driving car, but more than likely the signal was missing from Uber's database. Their lack of explanation for this failure does not inspire confidence in their approach.
That makes it hard for a person, especially if they're new to that road, but why would it affect the database lookup that a self-driving car is doing?