Steps used aboard ship in place of stairs. The angle of inclination for a vertical ladder should be between 75–90 degrees. Continuous ladders should not exceed 9.1m (30 ft) in height.
Further reading: ABS Guidance Notes for the “Application of Ergonomics to Marine Systems”, ABS Guide for “Means of Access to Tanks and Holds for Inspection” – can be downloaded from www.eagle.org