Joe Ryan, a veteran train engineer, is demoted to a flagman position after a disastrous crash-- one caused by his cowardly and opportunistic partner. Though Ryan's failing eyesight is named as the cause of the crash, he's undeterred as he designs an automatic braking invention.
Unfortunately the movie The Block Signal is not yet available on HBO Max.
| Directing | Frank O'Connor | Director |
| Writing | Edward J. Meagher | Scenario Writer |
| Writing | F. Oakley Crawford | Story |
| Writing | Frank O'Connor | Scenario Writer |
