How does the choice of stair tread nosing affect Building Regulations Document M compliance?

Under Building Regulations Part M (Access to and use of buildings), stair treads in public and commercial settings must feature a visually contrasting nosing on every step to assist visually impaired users. The nosing must measure between 55mm and 65mm on both the tread and the riser. Additionally, the material must match or exceed the slip resistance of the rest of the tread to prevent traction transitions at the most critical point of foot contact.