9 CFR 88.3 - Standards for conveyances.
(1) Be designed, constructed, and maintained in a manner that at all times protects the health and well-being of the equines being transported (e.g., provides adequate ventilation, contains no sharp protrusions, etc.);
(2) Include means of completely segregating each stallion and each aggressive equine on the conveyance so that no stallion or aggressive equine can come into contact with any of the other equines on the conveyance;
(4) Be equipped with doors and ramps of sufficient size and location to provide for safe loading and unloading.
(b) Equines for slaughter must not be transported in any conveyance that has the animal cargo space divided into two or more stacked levels, except that conveyances lacking the capability to convert from two or more stacked levels to one level may be used until December 7, 2006. Conveyances with collapsible floors (also known as “floating decks”) must be configured to transport equines on one level only.