Final answer:
A driver should stop at least 15 feet from the nearest rail at a railroad crossing to ensure safety. This distance allows for adequate time to react should a train be approaching and corresponds to about one car-length.
Step-by-step explanation:
At a railroad crossing, a driver should stop no less than 15 feet from the nearest rail. This is to ensure safety because a train, being a massive object, can create strong air currents and might extend beyond the rails. Also, stopping far enough away provides the driver with adequate time to observe if a train is approaching and react accordingly. The exact distance may vary depending on local laws, so it's always important to check the specific rules in your area.
For example, one car-length is typically considered to be about 15 to 20 feet. So this means you should stop at least one car length away from the nearest rail.
This rule is part of general road safety, similar to how you must stop at a red traffic light. Although there are emergency situations where rules can be broken for greater good, as in the case of a pregnant woman going to the hospital, safety at railroad crossings does not have such exceptions due to the high risk involved.