It would be near impossible for a locomotive to pull an entire train at once from a dead start because the combined static friction would be too great, but if the locomotive starts by pulling just one car at a time and gradually adds weight, then a single SD40-2 locomotive can pull miles worth of rail cars.

A truck trying to pull a million pounds of semi-trailers would fail because the static friction between the trailer tires and the road would be too much to overcome due to excessive contact area, whereas an electric F-150 successfully pulled a million pounds of railroad auto racks because rail cars have minimal friction.

The ability of locomotives to pull enormous loads is a combination of: overcoming static friction by adding weight gradually, taking advantage of extremely low rolling friction, and using exceptionally powerful traction motors.

The contact area between the top of the rail and the bottom of train wheels is only about the size of a dime, creating a very low friction environment that allows locomotives to pull massive loads.

Draft gears are located behind each coupler on a train and allow weight to be added gradually by letting the coupler slowly move in and out of a large sleeve, enabling locomotives to overcome static friction one car at a time.

A person can move a single rail car or locomotive nearly unaided due to the extremely low friction between rail equipment and rails, though this is dangerous and should not be attempted.

A typical SD78s locomotive weighs 428,000 pounds with 12 points of contact with the rails, meaning each wheel's contact area bears approximately 35,500 pounds of weight.

Locomotives are equipped with some of the most powerful traction motors on the market, which provide immense torque necessary to overcome friction and pull trains.

Static friction is the force that opposes the potential momentum of a stationary object, and any stationary object will remain in place until the static friction is overcome.

When a train comes to a complete stop, the static friction from hundreds of wheels makes it extremely difficult for locomotive engines to get everything moving, despite the extremely low rolling friction between cars and rails.

Draft gears can be audibly heard in action when trains are accelerating and decelerating, as the coupler slowly moves in and out of the sleeve.

On exponentially long trains, the engine might be moving at a couple miles per hour before the end of the train even starts to move due to the slack created by draft gears gradually adding weight one car at a time.

Draft gears allow locomotives to overcome static friction one car at a time, which is why a single locomotive can pull thousands of tons of rail cars as if it were nothing.