Final answer:
A potential disciplinary action for failing to follow a written safety program is a fine, which is a direct monetary penalty used to enforce compliance with safety regulations.
Step-by-step explanation:
If a carrier fails to follow a written safety program, a possible disciplinary action that might be assessed could be a fine. This is because failing to comply with safety protocols can lead to unsafe working conditions or endanger public safety, which regulatory bodies such as transportation departments seek to prevent with various enforcement actions. While driver suspension, vehicle impoundment, and loss of insurance coverage are potential outcomes, a fine is a direct monetary penalty that is often utilized as an immediate response to non-compliance with safety requirements.