A more thorough explanation:

The National Transportation Safety Board (NTSB) is an independent federal agency consisting of five members. It investigates accidents involving air, rail, water, highway, pipeline, and hazardous-waste transportation. The NTSB also conducts studies and makes recommendations to government agencies, transportation industries, and others on safety measures and practices.

• The NTSB investigates a plane crash to determine the cause and make recommendations to prevent similar accidents in the future.
• The NTSB studies the safety of a new type of train technology and recommends changes to improve its safety.
• The NTSB investigates a pipeline explosion and makes recommendations to prevent future accidents.

These examples illustrate how the NTSB investigates accidents and makes recommendations to improve transportation safety. By studying accidents and making recommendations, the NTSB helps prevent future accidents and protect the public.