IMO it's failing to look back at certain/critical points in the road layout
Almost all cyclists, with or without head-phones, fail to look behind them enough. This observation is based on hundreds of thousands of hours of riding in the city.
Thinking that you'll hear stuff coming up behind you, and therefore that you don't need to look is idiotic. Hybrid & electric cars make almost no sound, and a lot of the more expensive, new cars make very little. This is not even mentioning other cyclists.
Almost all cyclists, with or without head-phones, fail to look behind them enough. This observation is based on hundreds of thousands of hours of riding in the city.
Thinking that you'll hear stuff coming up behind you, and therefore that you don't need to look is idiotic. Hybrid & electric cars make almost no sound, and a lot of the more expensive, new cars make very little. This is not even mentioning other cyclists.