Placards
Reportable Quantities and the RQ Marking Explained
What a reportable quantity is, why the letters RQ appear on hazmat shipping papers, and how it ties into hazardous substances and spill reporting.
Lawrence Arya··5 min
Placards
Residue and Empty Tank Placarding: Empty Is Not Always Clear
Why an empty hazmat tank can still need placards, what the RESIDUE notation means, and the rule that catches CDL students off guard.
Lawrence Arya··5 min
Study tips
Spaced Repetition for CDL Study: Why Short Reps Win
Why short, spaced study sessions beat cramming for the CDL hazmat test, what the learning science says, and how to apply spaced repetition to placards.
Lawrence Arya··6 min
Placards
Subsidiary Hazard Placards Explained (No Class Number)
Some materials carry a second, subsidiary hazard. Here is what subsidiary placards mean, why they often have no class number, and when they are required.
Lawrence Arya··5 min
Test prep
The X Endorsement Explained (Tanker Plus Hazmat)
What the CDL X endorsement is, how it combines the tank vehicle and hazmat endorsements, and what it takes to earn it. A study guide for CDL drivers.
Lawrence Arya··5 min
Test prep
TWIC vs Hazmat Endorsement: What Is the Difference?
TWIC and the CDL hazmat endorsement both involve a TSA background check but serve different purposes. Here is how they differ and how they overlap.
Lawrence Arya··5 min
Placards
UN Numbers on Hazmat Placards Explained (and NA Numbers)
What the four-digit UN or NA identification number on a hazmat placard means, where it appears, how it differs from the hazard class, and how responders use it.
Lawrence Arya··5 min
Test prep
Understanding the Hazardous Materials Table (49 CFR 172.101)
How to read the Hazardous Materials Table, what each column tells you, and how shippers use it to classify a material. A CDL hazmat study guide.
Lawrence Arya··5 min
Placards
US vs International Hazard Placards (UN, ADR, TDG, IMDG)
Why hazmat placards look almost the same worldwide, how the US system relates to the UN model, and the main differences across ADR, TDG, IMDG, and IATA.
Lawrence Arya··5 min
Placards
What Does the DANGEROUS Placard Mean? Mixed Loads
The DANGEROUS placard explained: when a single mixed-load placard can replace several Table 2 placards, and the 2,205-pound exception that overrides it.
Lawrence Arya··5 min
Placards
What Is a Hazardous Material? The DOT Definition
How the U.S. Department of Transportation defines a hazardous material, how materials are classified, who decides, and how it relates to dangerous goods.
Lawrence Arya··5 min
Placards
What to Do in a Hazmat Emergency (Driver Basics)
The basic steps a driver takes in a hazmat emergency: secure the scene, warn others, use the shipping papers and ERG, and call for help safely.
Lawrence Arya··5 min