What are the effects of listening to loud music - especially with an extremely loud bass volume - in the car?

Loud music in the car can be a safety problem because it distracts you and reduces how well you perceive traffic. Your attention is significantly impaired because your brain has to process the strong sound stimulus, and you’re more likely to miss important cues like sirens, honking, unusual engine noises, or warning sounds from your own vehicle. Extremely loud bass can also cause physical vibration and stress, which further harms concentration and can lead to riskier, less smooth driving.

It can also negatively affect blind people near the car: very loud music, especially heavy bass, can mask the environmental sounds they rely on for orientation (traffic flow, footsteps, crossing signals, reflections of sound from buildings). That makes it harder for them to judge where vehicles are and how the street is laid out. So the effects in answers 1 and 2 are both relevant: it reduces driver attention and can disturb the orientation of blind pedestrians.