General requirements.

Link to an amendment published at 91 FR 49353, Aug. 4, 2026.#

(a)Packages secured in a motor vehicle. Any package containing any hazardous material, not permanently attached to a motor vehicle, must be secured against shifting, including relative motion between packages, within the vehicle on which it is being transported, under conditions normally incident to transportation. Packages having valves or other fittings must be loaded in a manner to minimize the likelihood of damage during transportation.#

(b)Each package containing a hazardous material bearing package orientation markings prescribed in § 172.312 of this subchapter must be loaded on a transport vehicle or within a freight container in accordance with such markings and must remain in the correct position indicated by the markings during transportation.#

(c)No smoking while loading or unloading. Smoking on or about any motor vehicle while loading or unloading any Class 1 (explosive), Class 3 (flammable liquid), Class 4 (flammable solid), Class 5 (oxidizing), or Division 2.1 (flammable gas) materials is forbidden.#

(d)Keep fire away, loading and unloading. Extreme care shall be taken in the loading or unloading of any Class 1 (explosive), Class 3 (flammable liquid), Class 4 (flammable solid), Class 5 (oxidizing), or Division 2.1 (flammable gas) materials into or from any motor vehicle to keep fire away and to prevent persons in the vicinity from smoking, lighting matches, or carrying any flame or lighted cigar, pipe, or cigarette.#

(e)Handbrake set while loading and unloading. No hazardous material shall be loaded into or on, or unloaded from, any motor vehicle unless the handbrake be securely set and all other reasonable precautions be taken to prevent motion of the motor vehicle during such loading or unloading process.#

(f)Use of tools, loading and unloading. No tools which are likely to damage the effectiveness of the closure of any package or other container, or likely adversely to affect such package or container, shall be used for the loading or unloading of any Class 1 (explosive) material or other dangerous article.#

(g)[Reserved]#

(h)Precautions concerning containers in transit; fueling road units. Reasonable care should be taken to prevent undue rise in temperature of containers and their contents during transit. There must be no tampering with such container or the contents thereof nor any discharge of the contents of any container between point of origin and point of billed destination. Discharge of contents of any container, other than a cargo tank or IM portable tank, must not be made prior to removal from the motor vehicle. Nothing contained in this paragraph shall be so construed as to prohibit the fueling of machinery or vehicles used in road construction or maintenance.#

(i)Attendance requirements—(1) Loading. A cargo tank must be attended by a qualified person at all times when it is being loaded. The person who is responsible for loading the cargo tank is also responsible for ensuring that it is so attended.#

(2)Unloading. A motor carrier who transports hazardous materials by a cargo tank must ensure that the cargo tank is attended by a qualified person at all times during unloading. However, the carrier's obligation to ensure attendance during unloading ceases when:#

(i)The carrier's obligation for transporting the materials is fulfilled;#

(ii)The cargo tank has been placed upon the consignee's premises; and#

(iii)The motive power has been removed from the cargo tank and removed from the premises.#

(3)A qualified person “attends” the loading or unloading of a cargo tank only if, throughout the process:#

(i)Except for unloading operations subject to §§ 177.837(d) and 177.840(p) and (q), the qualified person is within 7.62 m (25 feet) of the cargo tank. The qualified person attending the unloading of a cargo tank must be alert and have an unobstructed view of the cargo tank and delivery hose to the maximum extent practicable during the unloading operation; or#

(ii)The qualified person observes all loading or unloading operations by means of video cameras and monitors or instrumentation and signaling systems such as sensors, alarms, and electronic surveillance equipment located at a remote control station, and the loading or unloading system is equipped as follows:#

(A)For a video monitoring system used to meet the attendance requirement, the camera must be mounted so as to provide an unobstructed view of all equipment involved in the loading or unloading operations, including all valves, hoses, domes, and pressure relief devices;#

(B)For an instrumentation and signaling system used to meet the attendance requirement, the system must provide a surveillance capability at least equal to that of a human observer;#

(C)Upon loss of video monitoring capability or instrumentation and signaling systems, loading or unloading operations must be immediately terminated;#

(D)Shut-off valves operable from the remote control station must be provided;#

(E)In the event of a remote system failure, a qualified person must immediately resume attending the loading or unloading of the cargo tank as provided in paragraph (i)(3)(i) of this section;#

(F)A containment area must be provided capable of holding the contents of as many cargo tank motor vehicles as might be loaded at any single time; and#

(G)A qualified person must personally conduct a visual inspection of each cargo tank motor vehicle after it is loaded, prior to departure, for any damage that may have occurred during loading; or#

(iii)Hoses used in the loading or unloading operations are equipped with cable-connected wedges, plungers, or flapper valves located at each end of the hose, able to stop the flow of product from both the source and the receiving tank within one second without human intervention in the event of a hose rupture, disconnection, or separation.#

(A)Prior to each use, each hose must be inspected to ensure that it is of sound quality, without defects detectable through visual observation; and#

(B)The loading or unloading operations must be physically inspected by a qualified person at least once every sixty (60) minutes.#

(4)A person is “qualified” if he has been made aware of the nature of the hazardous material which is to be loaded or unloaded, has been instructed on the procedures to be followed in emergencies, and except for persons observing loading or unloading operations by means of video cameras and monitors or instrumentation and signaling systems such as sensors, alarms, and electronic surveillance equipment located at a remote control station and persons inspecting hoses in accordance with paragraph (i)(3)(iii) of this section, is authorized to move the cargo tank, and has the means to do so.#

(j)Except for a cargo tank conforming to § 173.29(b)(2) of this subchapter, a person may not drive a cargo tank motor vehicle containing a hazardous material regardless of quantity unless:#

(1)All manhole closures are closed and secured; and#

(2)All valves and other closures in liquid discharge systems are closed and free of leaks, except external emergency self-closing valves on MC 338 cargo tanks containing the residue of cryogenic liquids may remain either open or closed during transit.#

(k)[Reserved]#

(l)Use of cargo heaters when transporting certain hazardous material. Transportation includes loading, carrying, and unloading.#

(1)When transporting Class 1 (explosive) materials. A motor vehicle equipped with a cargo heater of any type may transport Class 1 (explosive) materials only if the cargo heater is rendered inoperable by: (i) Draining or removing the cargo heater fuel tank; and (ii) disconnecting the heater's power source.#

(2)When transporting certain flammable material—(i) Use of combustion cargo heaters. A motor vehicle equipped with a combustion cargo heater may be used to transport Class 3 (flammable liquid) or Division 2.1 (flammable gas) materials only subject to the following conditions:#

(A)The combustion cargo heater is powered by diesel fuel or propane and each of the following requirements are met:#

(1)Electrical apparatus in the cargo compartment is non-sparking or explosion proof.#

(2)There is no combustion apparatus in the cargo compartment.#

(3)There is no connection for return of air from the cargo compartment to the combustion apparatus.#

(4)The heating system will not heat any part of the cargo to more than 54 °C (130 °F).#

(5)Heater requirements under § 393.77 of this title are complied with.#

(6)The heater unit and its fuel supply must be externally mounted on the truck or trailer.#

(7)The heater unit must retain combustion in a sealed combustion chamber.#

(8)The heater unit must utilize outside air for combustion (air from the cargo space cannot be used for combustion).#

(9)Heater unit combustion gases must be exhausted to the outside of the truck or trailer.#

(B)The combustion cargo heater is a catalytic heater and each of the following requirements are met:#

(1)The heater's surface temperature cannot exceed 54 °C (130 °F)—either on a thermostatically controlled heater or on a heater without thermostatic control when the outside or ambient temperature is 16 °C (61 °F) or less.#

(2)The heater is not ignited in a loaded vehicle.#

(3)There is no flame, either on the catalyst or anywhere in the heater.#

(4)The manufacturer has certified that the heater meets the requirements under paragraph (l)(2)(i)(B) of this section by permanently marking the heater “MEETS DOT REQUIREMENTS FOR CATALYTIC HEATERS USED WITH FLAMMABLE LIQUID AND GAS.”#

(5)The heater is also marked “DO NOT LOAD INTO OR USE IN CARGO COMPARTMENTS CONTAINING FLAMMABLE LIQUID OR GAS IF FLAME IS VISIBLE ON CATALYST OR IN HEATER.”#

(6)Heater requirements under § 393.77 of this title are complied with.#

(ii)[Reserved]#

(iii)Restrictions on automatic cargo-space-heating temperature control devices. Restrictions on these devices have two dimensions: Restrictions upon use and restrictions which apply when the device must not be used.#

(A)Use restrictions. An automatic cargo-space-heating temperature control device may be used when transporting Class 3 (flammable liquid) or Division 2.1 (flammable gas) materials only if each of the following requirements is met:#

(1)Electrical apparatus in the cargo compartment is nonsparking or explosion proof.#

(2)There is no combustion apparatus in the cargo compartment.#

(3)There is no connection for return of air from the cargo compartment to the combustion apparatus.#

(4)The heating system will not heat any part of the cargo to more than 54 °C (129 °F).#

(5)Heater requirements under § 393.77 of this title are complied with.#

(B)Protection against use. Class 3 (flammable liquid) or Division 2.1 (flammable gas) materials may be transported by a vehicle, which is equipped with an automatic cargo-space-heating temperature control device that does not meet each requirement of paragraph (l)(2)(iii)(A) of this section, only if the device is first rendered inoperable, as follows:#

(1)Each cargo heater fuel tank, if other than LPG, must be emptied or removed.#

(2)Each LPG fuel tank for automatic temperature control equipment must have its discharge valve closed and its fuel feed line disconnected.#

(m)Tanks constructed and maintained in compliance with Spec. 106A or 110A (§§ 179.300, 179.301 of this subchapter) that are authorized for the shipment of hazardous materials by highway in part 173 of this subchapter must be carried in accordance with the following requirements:#

(1)Tanks must be securely chocked or clamped on vehicles to prevent any shifting.#

(2)Equipment suitable for handling a tank must be provided at any point where a tank is to be loaded upon or removed from a vehicle.#

(3)No more than two cargo carrying vehicles may be in the same combination of vehicles.#

(4)Compliance with §§ 174.200 and 174.204 of this subchapter for combination rail freight, highway shipments and for trailer-on-flat-car service is required.#

(n)Specification 56, 57, IM 101, and IM 102 portable tanks, when loaded, may not be stacked on each other nor placed under other freight during transportation by motor vehicle.#

(o)Unloading of IM and UN portable tanks. No person may unload an IM or UN portable tank while it remains on a transport vehicle with the motive power unit attached except under the following conditions:#

(1)The unloading operation must be attended by a qualified person in accordance with the requirements in paragraph (i) of this section. The person performing unloading functions must be trained in handling emergencies that may occur during the unloading operation.#

(2)Prior to unloading, the operator of the vehicle on which the portable tank is transported must ascertain that the conditions of this paragraph (o) are met.#

(3)An IM or UN portable tank equipped with a bottom outlet as authorized in Column (7) of the § 172.101 Table of this subchapter by assignment of a T Code in the appropriate proper shipping name entry, and that contains a liquid hazardous material of Class 3, PG I or II, or PG III with a flash point of less than 100 °F (38 °C); Division 5.1, PG I or II; or Division 6.1, PG I or II, must conform to the outlet requirements in § 178.275(d)(3) of this subchapter.#

Editorial Note:For Federal Register citations affecting § 177.834, see the List of CFR Sections Affected, which appears in the Finding Aids section of the printed volume and at www.govinfo.gov.#