Final answer:
Drivers should stop at a distance that allows for safe braking when they see active railroad crossing devices, considering factors like road conditions, perception and reaction time.
Step-by-step explanation:
The correct answer is that the distance at which you should stop when you see active crossing devices at a railroad crossing can vary, depending on several factors like road conditions and driver reaction time.
However, it is generally advised to stop within a distance that allows for ample time to safely halt the vehicle and avoid any possible collision.
This stopping distance must take into account the driver's perception time, the reaction time and the vehicle's braking capability, which can differ on dry or wet pavement.
For example, if a car is initially traveling at 30.0 m/s, the braking distance could be calculated based on the reaction time and the road condition.
It is also important to obey traffic signals such as railroad crossing lights to ensure pedestrian safety and to avoid dangerous and potentially illegal scenarios such as crossing against a signal.
The correct answer is option 3 car-lengths. When you see active crossing devices at a railroad crossing, you should stop your vehicle at a distance that is equivalent to 3 car-lengths away from the crossing.
This distance allows for a safe stopping distance and gives you enough time to react and avoid any potential collision with a train.
Obeying these signals is crucial for pedestrian safety and avoiding potential accidents.