Question

which is an invention that improved safety for railway passengers?
refrigerated rail cars
pullman sleeping cars
time standardization
air brakes

Explanation:

• Refrigerated rail cars preserved perishable goods, not passenger safety.
• Pullman sleeping cars improved passenger comfort, not safety.
• Time standardization reduced scheduling confusion but was not a direct safety invention for passengers.
• Air brakes allowed trains to stop quickly and uniformly, drastically reducing collisions and accidents, directly improving passenger safety.

Answer:

air brakes