jesenia: There's no way to answer that without knowing the speed and weight of the train. The type of cars will also alter the stopping distance. At 70 mph a 6,000 ton train could easily need a mile to a mile and a half to stop.
Depending on speed about the length of the train would be a reasonable guess.
It really does have a different braking distance if the train is going 5 Mph or 60 MPH. Loaded or empty is also very important.
You can be safe in knowing should you stand in front of it you only need to worry about the first few inches crushing you.
The rest of anything that passes over is just emphasis on your stupidity of racing a train to the crossing.
The rail industry assumes a loaded freight train takes at least one mile to stop. Be it 5 feet shorter or longer really does not matter.
Not that many trains are 8000 feet long.
Those 100 plus car trains prepare to stop many miles before they need to.With a gradual reduction in speed.
An emergency stop of a train that long can frequently result in a breakup somewhere near the back of the train.
An empty train car weighs about 100,000 pounds a train this long would have 100 or more cars in it.
At a service rate of brake pipe reduction that sets the brakes, the air propagates through the brake pipe at 500ft per second, rounded off. So, with your 8000ft train, it will take 16 seconds before the brakes even start to set up on the last car. Emergency rate of brake pipe reduction is 1,000ft per second.
So, if that train is running at 60mph, you've eaten up a quarter mile before the brakes are even set through the whole train. This provides minimal braking and basically sets the slack in the train and further light reductions are usually needed as the train begins to respond.
As Andy points out, the tonnage of the train is a major factor. In your example, a train that long is probably a pig and probably in the neighborhood 0f 6,000 tons.
Bottom line, it goes without saying, if I can see you, it is already too late to stop short of you. As a side note, the train doesn t have to be moving at high speed to nail you. In fact, most vehicular and pedestrian fatalities occur when the train is travelling at or less than 30mph.
And a sunny day helps. The brakes do not work as well in very cold weather and keeping the train charged with air can be problematic the further back you go.
Stopping distance is calculated using the equation :-
d = v^2 / 2µg
Where d is the stopping distance, v is the velocity, µ is the kinetic coefficient of friction, g is gravity.
For dry hard steel on hard dry steel, the value of µ is 0.42. The value of g is 32.17405 ft/s2 (Imperial System.)
As you have not quoted a value for v, d cannot be resolved.
Insert the missing value into the equation. To obtain a value in feet, use Imperial dimensions.
Edit. Mass (weight) does not come into the equation. The greater the mass, the greater the contact load between wheels and rail and thus the braking force which can be applied on level track before locking-up the brakes. Please feel free to give thumbs down if you think that Newton got it wrong.
Just quite a lot.
Mmmm – maybe the speed and weight of the train will be important too not just its length and the weather conditions don't you think?