Which of the following blocks the smooth flow of traffic?

Slowing down to look at a collision scene significantly disrupts the smooth flow of traffic. When drivers reduce their speed to observe an incident on the roadway, it creates a ripple effect, causing those behind them to slow down as well. This unexpected deceleration can lead to congestion and potentially increase the risk of additional accidents, as drivers may become distracted or react unpredictably.

In contrast, using turn signals is a safe practice that informs other drivers of your intentions, thus contributing to smoother traffic movement. Driving at a constant speed helps maintain a predictable driving environment, allowing other vehicles to gauge their distance and speed accurately. Maintaining a safe following distance is crucial for ensuring adequate reaction time and preventing collisions, which also aids in the overall flow of traffic. Each of these practices enhances safety and traffic efficiency, while slowing down to gawk at accidents hinders it.