Final answer:
Drivers should look ahead 12-15 seconds in urban areas and 20-30 seconds on highways to avoid last-minute braking. Stopping distance is influenced by speed, road conditions, and driver reaction time, which should be included in calculations when determining if a vehicle was exceeding the speed limit.
Step-by-step explanation:
The question is asking about the appropriate reaction time and braking distance for a vehicle to avoid last-minute braking. Typically, it's recommended that drivers look ahead between 12-15 seconds for urban or street driving, and for highway driving, it's usually around 20-30 seconds. However, these numbers can vary based on road conditions, speed, and the driver's attention.
For example, if you drive a car at exactly 50 mph and apply the brakes until it stops, both the time and the distance taken to stop are critical factors. Tests indicate that at 50 mph, the average distance to stop a vehicle might range between 140-170 feet in normal conditions.
With a reaction time included, for instance, a 0.5-second response time would add additional feet to the total stopping distance.
In situations where a factor such as the coefficient of friction is known (for example, 0.55), it's possible to calculate whether a car skidding to a stop over a certain distance was exceeding a specific speed limit, which could be a consideration in legal matters such as fighting a speeding ticket in court.