Who or what deserves praise for the car's actions to reduce congestion and air pollution? And who or what deserves blame for the pedestrian's injuries?

One possibility is the self-driving taxi's designer or developer. But in many cases, they wouldn't have been able to predict the taxi's exact behavior. In fact, people typically want artificial intelligence to discover some new or unexpected idea or plan. If we know exactly what the system should do, then we don't need to bother with AI.

Alternatively, perhaps the taxi itself should be praised and blamed. However, these kinds of AI systems are essentially deterministic: Their behavior is dictated by their code and the incoming sensor data, even if observers might struggle to predict that behavior. It seems odd to morally judge a machine that had no choice.