Final answer:
The best distance rule to use on dry roads is the 3-second rule. The correct answer is option a.
Step-by-step explanation:
Understanding the Safe Following Distance on Dry Roads
When determining the safest following distance on dry roads, a commonly used method is the 3-second rule. This rule suggests that when driving under good conditions, a driver should stay at least three seconds behind any vehicle that is directly in front of the driver's vehicle. The method for checking this is to observe when the rear of the vehicle ahead passes a stationary object on the side of the road; the driver then counts how long it takes for the front of their own vehicle to reach the same object. There should at least be a three-second interval in this count.
Bridget's observation from her classroom window aligns with this rule of thumb. If cars are taking about 3 seconds to travel 50 meters, and if we assume that they are traveling at a typical city speed limit, this timing might be suitable for a safe following distance in ideal conditions. The 3-second rule accommodates for the time taken during a driver's reaction time before braking, which accounts for a constant velocity travel before the actual deceleration begins when reacting to a potential hazard.
The concept of the following distance is significant as it provides the time needed to react to sudden changes and to safely stop without colliding with the vehicle ahead. This is particularly important as response time, combined with the vehicle's stopping distance, factors into how quickly a vehicle can be brought to a standstill in an emergency. For instance, at a speed of 30.0 m/s (which is roughly 108 km/h), a driver's reaction time of 0.500 seconds adds significantly to the total stopping distance required, which is why maintaining an adequate following distance even in dry conditions is crucial.
Thus, for the given choices and typical dry road conditions, the best distance rule to follow would be option a, the 3-second rule.