The transportation of batteries in the United States is governed by stringent regulations to ensure safety and mitigate risks associated with hazardous materials. The U.S. Department of Transportation (DOT) and its sub-agency, the Pipeline and Hazardous Materials Safety Administration (PHMSA), oversee these regulations under the Hazardous Materials Regulations (HMR). These rules apply to ground transportation, including road and rail, and cover classification, packaging, labeling, placarding, and training requirements.

**Classification Under Hazardous Materials Regulations (HMR)**
Batteries are classified based on their chemistry, size, and potential hazards. The HMR categorizes them under Class 9 (Miscellaneous Hazardous Materials) if they meet specific criteria. Lithium-ion and lithium-metal batteries, due to their flammability and thermal runaway risks, are subject to strict controls. Lead-acid and nickel-based batteries are also regulated but under different hazard classifications depending on their electrolyte and construction.

Lithium batteries are further divided into:
- UN3480 (Lithium-ion batteries)
- UN3481 (Lithium-ion batteries packed with equipment)
- UN3481 (Lithium-ion batteries contained in equipment)
- UN3090 (Lithium-metal batteries)
- UN3091 (Lithium-metal batteries packed with equipment)
- UN3091 (Lithium-metal batteries contained in equipment)

Each classification determines packaging, labeling, and documentation requirements.

**Packaging Standards**
Batteries must be packaged in UN-certified containers that meet performance criteria for drop tests, stacking tests, and pressure differentials. The packaging must prevent short circuits, movement, and damage during transit. For lithium batteries, additional requirements include:
- Inner packaging that prevents contact with conductive materials.
- Cushioning to absorb shocks.
- Outer packaging marked with the appropriate UN number and hazard class.

Small lithium cells and batteries (under certain watt-hour or gram limits) may qualify for exceptions but still require robust packaging. Damaged or defective batteries are subject to more stringent packaging rules due to higher risks.

**Labeling and Placarding**
All hazardous material shipments, including batteries, must display proper labels and placards. Lithium battery shipments require:
- Class 9 hazard labels.
- Lithium battery handling labels (for smaller shipments).
- UN number and proper shipping name on packages.

For larger quantities, transport vehicles must display Class 9 placards. Shipping papers must include the proper description, UN number, and emergency contact information.

**Driver Training Requirements**
The DOT mandates hazardous materials training for drivers transporting batteries under HMR. Training includes:
- General awareness of hazardous materials regulations.
- Function-specific training for battery handling.
- Safety procedures for leaks, fires, or thermal runaway events.
- Emergency response protocols.

Training must be renewed every three years, with additional requirements for drivers carrying larger quantities of hazardous materials.

**Comparison with ADR (Europe)**
The European Agreement concerning the International Carriage of Dangerous Goods by Road (ADR) shares similarities with U.S. regulations but has key differences:
- Classification: ADR also classifies lithium batteries under Class 9 but includes additional subcategories for specific risks.
- Packaging: ADR requires UN-certified packaging but may impose different testing standards.
- Labeling: ADR uses similar hazard labels but may require additional markings in multiple languages.
- Training: ADR mandates driver training but with periodic refresher courses every five years instead of three.

A notable difference is that ADR imposes stricter limits on the quantity of lithium batteries per transport unit, while U.S. regulations provide more flexibility for smaller shipments.

**Enforcement and Penalties**
Non-compliance with DOT/PHMSA regulations can result in significant fines, shipment delays, or criminal liability. Common violations include improper packaging, missing labels, or inadequate documentation. Companies must maintain records of training, shipping papers, and incident reports for inspections.

**Conclusion**
The U.S. DOT and PHMSA regulations for ground transportation of batteries are comprehensive, emphasizing safety through strict packaging, labeling, and training protocols. While international frameworks like ADR align in many areas, regional differences in testing, labeling, and training cycles exist. Compliance is critical to ensuring safe transport and avoiding regulatory penalties.