36 CFR Part 1195 Standards for Accessible Medical Diagnostic Equipment

M305.2.2.2 Side Transfer Supports.

Transfer supports for transfer surfaces complying with M301.2.3.2 shall be 28 inches (710 mm) long minimum and shall be positioned along the width of transfer surfaces.

EXCEPTIONS: 1. Where transfer surfaces are part of an articulating surface, the support shall be permitted to be 15 inches (380 mm) long minimum. 
2. Where the width of an imaging bed is more than 24 inches (533 mm), transfer supports shall be permitted to be 12 inches (305 mm) long minimum.