"Futurerail (Popular Mechanics, June 1988)" by John Berkey

Upscaled hi-res version 5120x3626

Sources:

• Fan website: Popular Mechanics Art - John Berkey Art

::: spoiler with a picture of the magazine & poster :::

• Scanned by Humanoid History (@HumanoidHistory) - Nitter link

• Upscaled hi-res version and scan attribution found on reddit: u/acoolrocket comments on Futurerail by John Berkey (1988)