Which of the following is a sign of impaired driving?

Impaired driving often results in erratic behavior on the road, which can manifest as excessive braking or acceleration. This can indicate a lack of control and a delayed response to traffic conditions, commonly associated with being under the influence of alcohol or drugs. A driver who is impaired may not be able to gauge speed and distance appropriately, leading to sudden stops or rapid acceleration that disrupts the flow of traffic and can be hazardous to other road users.

In contrast, driving at a consistent speed and obeying traffic signals typically reflect responsible driving behavior, as these actions demonstrate an understanding of and adherence to road rules. Frequent lane changes might suggest a degree of recklessness or impatience, but they don’t directly indicate impairment as driving can be erratic yet sober. Therefore, the distinctive behavior of excessive braking or acceleration is a clear sign of impaired driving, making it the correct choice in this context.