46 CFR 11.211(d)
Service on Articulated Tug Barges (ATBs) and Integrated Tug Barges (ITBs). Service on ATB or Dual Mode ITB units is creditable for an original deck officer endorsement or raise of grade of any deck officer endorsement. Service on an ATB or Dual Mode ITB with an aggregate tonnage of 1,600 GRT/3,000 GT or more is creditable on a two-for-one basis (2 days experience equals 1 day of creditable service) for up to 50 percent of the total service on vessels of 1,600 GRT/3,000 GT or more required for an unlimited officer endorsement. The remaining required service on vessels of more than 1,600 GRT/3,000 GT must be obtained on conventional vessels or Push Mode ITBs.
# 46 CFR § 10.107 - Definitions in subchapter B
Push-mode ITBs means those ITBs that involve a rigid coupling system and, when not coupled to the barge are incapable of conducting towing in any other configuration (such as astern or alongside) because, by themselves, they have very limited seakeeping capability. The propelling unit moves as one with the barge unit.
The Coast Guard recognizes that there are significant differences among the various vessel combinations covered by the ITB definition. For this reason, ITBs are divided into two groups: Pushing Mode ITBs and Dual Mode ITBs
Safety regulations and statutory requirements dependent on tonnage measurements are applicable to Pushing Mode ITBs as determined by the aggregate tonnage of the ITB combination…In other words Push Mode ITBs are pretty much treated regulatory wise as a single entity.