A track inspector finds a flat spot 4 inches long. How fast may you move the train to the first available set out location?

A track inspector finds a flat spot 4 inches long. How fast may you move the train to the first available set out location?

• A. 10 MPH
• B. 5 MPH
• C. 15 MPH
• D. 20 MPH

Answer: (A)

When a wheel has a flat spot, crossing it creates a bump that can jolt the train and increase the risk of wheel damage or derailment. The 4-inch length defines how long that bump lasts, so you choose a speed low enough to keep the dynamic forces manageable as you pass the defect toward the first set-out location. Ten miles per hour is the safe, allowed pace for crossing a small 4-inch flat spot, balancing safety with practical movement. Going slower (five mph) is overly cautious for this defect size, while faster speeds (fifteen or twenty mph) would raise the risk of damage or derailment. So you should move at 10 mph.

When a wheel has a flat spot, crossing it creates a bump that can jolt the train and increase the risk of wheel damage or derailment. The 4-inch length defines how long that bump lasts, so you choose a speed low enough to keep the dynamic forces manageable as you pass the defect toward the first set-out location. Ten miles per hour is the safe, allowed pace for crossing a small 4-inch flat spot, balancing safety with practical movement. Going slower (five mph) is overly cautious for this defect size, while faster speeds (fifteen or twenty mph) would raise the risk of damage or derailment. So you should move at 10 mph.