Train Handling and Performance Flashcards
7 cards from real LEC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Train Handling and Performance flashcards as text
How does increased train length affect the propagation speed of a brake pipe pressure change?
Answer: Longer trains experience slower brake response at the rear due to greater pipe length
In longer trains, the brake signal must travel farther through the brake pipe, causing rear cars to respond later than head-end cars.
What is the purpose of a 'precautionary brake application' when approaching a meeting point?
Answer: To ensure the train can stop before the siding switch if the opposing train has not cleared
A precautionary brake application ensures the engineer can stop short of a switch if an opposing train has not fully cleared the main track.
Which factor has the greatest influence on the amount of locomotive tractive effort available at a given speed?
Answer: The number of powered axles and adhesion coefficient
Tractive effort is limited by the product of axle load, number of powered axles, and the wheel-to-rail adhesion coefficient.
When should an engineer 'notch up' (increase throttle) after a speed restriction?
Answer: Only after the entire train has cleared the end of the restriction zone
Speed restrictions apply to the entire train, so throttle increase is permissible only after the last car clears the end of the restricted zone.
What is the result of making a brake pipe reduction that is too large when initially applying brakes on a heavy freight train?
Answer: Air flow from the brake pipe may cause emergency applications at the rear
An excessively large initial reduction can cause the rear cars' triple valves to sense an emergency rate of pressure drop and initiate emergency applications.
In train handling, what is 'bunching' and what hazard does it create?
Answer: Compressive slack accumulation that can cause derailments or coupler failures
Bunching occurs when slack runs in and couplers are in compression, creating buff forces that can kink or derail cars, especially on curves.
How does grade resistance affect the horsepower required to maintain a constant speed?
Answer: Grade resistance reduces required horsepower on descending grades and increases it on ascending grades
On an ascending grade, gravity adds to rolling resistance requiring more power; on a descending grade, gravity assists movement, requiring less power or braking.