---
kind: "section"
citation: "49 C.F.R. § 523.10"
title: "49"
number: "523.10"
heading: "Heavy-duty trailers."
url: "https://uscodex.org/cfr/49/523.10"
---

# §523.10. Heavy-duty trailers.

- (a) A trailer means a motor vehicle with or without motive power, designed for carrying cargo and for being drawn by another motor vehicle as defined in [49 CFR 571.3](/cfr/49/571.3.md). For the purpose of this part, heavy-duty trailers include only those trailers designed to be drawn by a truck tractor excluding non-box trailers other than flatbed trailer, tanker trailers and container chassis and those that are coupled to vehicles exclusively by pintle hooks or hitches instead of a fifth wheel. Heavy-duty trailers may be divided into different types and categories as follows:
  - (1) Box vans are trailers with enclosed cargo space that is permanently attached to the chassis, with fixed sides, nose, and roof. Tank trailers are not box vans.
  - (2) **Box van with front-mounted HVAC systems are refrigerated vans.** Note that this includes systems that provide cooling, heating, or both. All other box vans are dry vans.
  - (3) **Trailers that are not box vans are non-box trailers.** Note that the standards for non-box trailers in [49 CFR 535.5(e)(2)](/cfr/49/535.5.md?p=e-2) apply only to flatbed trailers, tank trailers, and container chassis.
  - (4) **Box van with a length greater than 50 feet are long box vans.** Other box vans are short box vans.
  - (5) **The following types of equipment are not trailers—**
    - (i) **Containers that are not permanently mounted on chassis.**
    - (ii) **Dollies used to connect tandem trailers.**
    - (iii) **Equipment that serves similar purposes but are not intended to be pulled by a tractor.**
- (b) Heavy-duty trailers do not include trailers excluded in [49 CFR 535.3](/cfr/49/535.3.md).

## Notes

### Amendments

[81 FR 74237, Oct. 25, 2016]

### Authority

Authority: 49 U.S.C. 32901; delegation of authority at 49 CFR 1.95.

### Amendments

[81 FR 74237, Oct. 25, 2016]