Final answer:
A minimum of a three-second following distance should be maintained behind the vehicle ahead for safety, accommodating for conditions such as wet roads and increased speeds, which significantly influence the total stopping distance.
Step-by-step explanation:
Normally, a minimum of three seconds distance should be maintained behind the vehicle ahead to ensure safe stopping distance. This rule can help drivers adjust their following distance depending on the road conditions and their reaction time. If the road is wet, the distance should be increased to allow for longer braking distances. Likewise, faster traveling speeds require longer following distances because the distance necessary to stop a car varies greatly with speed.
Understanding reaction time is also crucial for road safety. Assuming an average driver reaction time of 0.500 s, this needs to be factored in when calculating the total stopping distance, as well as the actual braking distance on both dry and wet pavement. For example, at a speed of 30.0 m/s, it's essential to consider these factors to avoid collisions.
When considering pedestrian safety, such as deciding when it's safe to cross the road in front of an oncoming vehicle, it is essential to measure the distance in car lengths. Given that the length of the average car is 3.5 m and pedestrians should cross at least 4 m ahead of the car, it's necessary to calculate the distance and time required to cross safely, factoring in the vehicle's speed and the pedestrian's walking speed.