The 90 class were designed specifically for heavy coal haulage in the Lower Hunter Valley region of New South Wales, to meet the required specifications the class was designed with much heavier frames than typical for locomotives then in use specifically to increase their tractive effort.
In the Lower Hunter Valley region of New South Wales, the 90 class locomotives were designed with enhanced capabilities to handle heavy coal haulage demands, featuring heavier frames than typical locomotives of that era, which allowed them to generate greater traction force.