49 CFR § 174.85 - Position in train of placarded cars, transport vehicles, freight containers, and bulk packagings.
(a) Except as provided in paragraphs (b) and (c) of this section, the position in a train of each loaded placarded car, transport vehicle, freight container, and bulk packaging must conform to the provisions of this section.
(b) A car placarded “RADIOACTIVE” must comply with train positioning requirements of paragraph (d) of this section and must be separated from a locomotive, occupied caboose, or carload of undeveloped film by at least one non-placarded car.
(c) A tank car containing the residue of a hazardous material must be separated from a locomotive or occupied caboose by at least one rail car other than a placarded tank car.
(d) Position of rail cars in a train. In the following table:
Position in Train of Placarded Cars Transporting Hazardous Materials
| RESTRICTIONS | Placard Group 1 | Placard Group 2 | Placard Group 3 | Placard Group 4 | ||
|---|---|---|---|---|---|---|
| Rail Car | Tank Car | Rail Car | Tank Car | Rail Car | Rail Car | |
| 1. When train length permits, placarded car may not be nearer than the sixth car from the engine or occupied caboose | X | X | X | |||
| 2. When train length does not permit, placarded car must be placed near the middle of the train, but not nearer than the second car from an engine or occupied caboose | X | X | X | |||
| 3. A placarded car may not be placed next to an open-top car when any of the lading in the open top car protrudes beyond the car ends, or if the lading shifted, would protrude beyond the car ends. | X | X | X | |||
| 4. A placarded car may not be placed next to a loaded flat car, except closed TOFC/COFC equipment, auto carriers, and other specially equipped cars with tie-down devices for securing vehicles. Permanent bulk head flat cars are considered the same as open-top cars | X | X | X | |||
| 5. A placarded car may not be placed next to any transport vehicle or freight container having an internal combustion engine or an open-flame device in operation. | X | X | X | |||
| 6. Placarded cars may not be placed next to each other based on the following: | ||||||
| Placard Group 1 | X | X | X | X | X | |
| Placard Group 2 | X | X | X | X | ||
| Placard Group 3 | X | X | X | X | ||
| Placard Group 4 | X | X | X | X | X | |
PLACARD GROUP:
Group 1—Divisions 1.1 and 1.2 (explosive) materials.
Group 2—Divisions 1.3, 1.4, 1.5 (explosive), Class 2 (compressed gas; other than Div 2.3, PG I, Zone A), Class 3 (flammable liquid), Class 4 (flammable solid), Class 5 (oxidizing), Class 6 (poisonous liquid; other than Div 6.1, PG I, Zone A), and Class 8 (corrosive) materials.
Group 3—Divisions 2.3 (Zone A; poisonous gas) and 6.1 (PG I, Zone A; poisonous liquid) materials.
Group 4—Class 7 (radioactive) materials.
(1) Where an “X” appears at the intersection of a Placard Group column and a Restriction row, the corresponding restriction applies.
(2) “Rail Car” means a car other than a tank car.
(3) For purposes of this subpart, each unit of an articulated intermodal rail car shall be considered as one car.