When Rail Lines ran Passenger Service some times they did not have enough passengers to warrant a full train so especially on Short Lines they ran Doodle Bugs . A Doodle Bug?
Yes this was the name given to single rail passenger car which was self propelled usually by Gasoline some where later unfitted to Diesel .
https://en.wikipedia.org/wiki/Doodlebug_(rail_car)
said to look like a insect and some say named after a common bug the Doodle Bug
https://www.atlasobscura.com/articles/what-the-hell-is-a-doodlebug
The rail units could also carry freight as well as served as rail ambulances even Funeral Cars
They would also get into accidents and one of the most Horrific Accidents in the Tri State Occurred near Cuyahoga Falls State Park in Ohio on July 31 ,1940
When a gasoline powered Doodle Bug owned by the Pennsylvania Railroad collided head on with a 73 unit of cars freight train coming the opposite direction. at the intersection of Front street and Hudson Drive Then just big open fields where Circus would set up. on its way from Hudson Ohio to Akron it has only left the station 10 minutes earlier.
https://en.wikipedia.org/wiki/Doodlebug_disaster
Upon impact at an estimated 55 MPH 43 of 46 passengers died almost instantly after the doodle bugs 350 gallon gas tank exploded and doodle bug caught fire.
https://www.youtube.com/watch?v=zRLtBS4g_RA
Miraculously the Doodle Bug Engineer survived having jumped and recalled he had orders to pull into the Hudson Siding to allow the freight train to pass but did not .
It was ruled that Carbon Monoxide getting into the cab area of the Doodle Bug had caused him confusion as crews complained of fumes with previous trips.\
The crash scene was horrific body's burned so bad they had to be sawed from their seats.
in 2005 a Memorial was placed near the scene.of the accident
Today modern signal systems are designed to stop train collisions but they still happen one several years ago near Philadelphia when an subway operator missed a switch.