Final answer:
For a 40 foot vehicle traveling at 35 mph on a dry road with good visibility, the minimum safe following distance is 4 seconds to allow sufficient reaction and braking time in case of an emergency stop.
Step-by-step explanation:
When you are driving a 40 foot vehicle at 35 mph with a dry road and good visibility, the minimum safe following distance is generally considered to be 4 seconds. This safety rule helps ensure that you have enough time to react and stop if necessary to avoid a collision. To calculate this, as a driver, you must watch for an object on the side of the road. When the rear end of the vehicle in front of you passes that object, begin counting seconds (one-thousand-one, one-thousand-two, etc.) until the front of your vehicle reaches the same object. If it takes less than 4 seconds, you're following too closely and should increase your distance.
In this scenario, the reaction time is assumed to be 0.500 seconds, during which the vehicle travels at a constant velocity. This duration is the time it takes for the driver to perceive a hazard and begin braking. Once the driver starts to brake, the stopping distance depends on the road conditions and vehicle's speed. For a vehicle moving at 35 mph, ensuring a 4-second gap allows additional distance for both the reaction time and the braking distance on dry pavement.