Train Driver Braking Systems and Train Dynamics 2

Question 1

Which factor has the greatest effect on increasing a train's stopping distance?

Accepted Answer

Train speed

Answer

Speed has the greatest effect because kinetic energy increases with the square of velocity, meaning doubling speed quadruples the energy that brakes must dissipate.

Question 2

What does 'percentage of braking' measure for a train?

Accepted Answer

The ratio of total braking force to total train weight

Answer

Percentage of braking is calculated as total braking force divided by total train weight, expressed as a percentage, and is used to determine expected stopping distances.

Question 3

Why does a fully loaded freight train require a longer stopping distance than an empty train traveling at the same speed?

Accepted Answer

Greater mass produces greater momentum that brakes must overcome

Answer

A loaded train has greater mass, resulting in greater momentum (mass × velocity), which requires more braking force and distance to stop at the same speed.

Question 4

What is 'brake lag' in a pneumatic train braking system?

Accepted Answer

The delay between the brake valve input and when brakes set throughout the train

Answer

Brake lag is the propagation delay for a pressure change to travel through the full length of the brake pipe, causing brakes to set sequentially from front to rear.

Question 5

What is the recommended braking strategy when approaching a long downgrade?

Accepted Answer

Control and reduce speed before entering the grade

Answer

Reducing speed before the grade prevents overheating brake shoes and gives the operator better speed control throughout the descent rather than reacting to runaway speed.

Train Driver Practice Test

Train Driver Practice Test

Train Driver Braking Systems and Train Dynamics 2