In order for you to play Train Fever on macOS with minimal graphics settings, your computer must meet the following requirements
Operating System:
OS X 10.7.5 or higher (NVIDIA), OS X 10.8.5 or higher (ATI/AMD)
Processor (CPU):
Intel Core 2 Duo
Memory (RAM):
2 GB RAM
Graphics Card:
Nvidia GeForce 8800 512 MB, ATI Radeon HD 3850 512 MB