Working, climbing or staying on a ladder is risky business and calls for a high level of slip resistance on the rungs as the footing is concentrated on a very small area.
Therefore, it is extra important to make sure that these steps are not smooth and slippery. If you slip, there is also the height factor to take into consideration.
Whether it is free standing or fixed, you will also be affected by using one or two hands to support yourself, whether you wear something, stand still and work or use it as an access point.
Self-bearing or built-in ladders will both demand the support of at least one hand. You also need to think about monkey ladder safety. Therefore, rungs must have good friction and anti-slip protection is vital!
Here is a useful quick guide on safety from Occupational Safety and Health Administration (OSHA).