Almost everyone has seen a train. Trains carry passengers and freight. Trains ride on tracks.

Old trains ran on steam. Lots of smoke came out the stack. This was from the fire used to make steam from water.

Today, trains are pulled by diesel engines. Diesels run on fuel (gas). They are cleaner than steam engines (very little smoke).

Some trains run on electricity. They are cleaner than diesels (no smoke).

Trains are much faster now. Modern trains are sleek. People use the same science to build trains and airplanes.

Most people ride in automobiles (cars). They make the air dirty. More people should ride on the train to keep the air clean.