Every plant hire van, landscaping pickup and service engineer’s truck in the country carries it: a can of petrol for the mower, diesel for the generator, an LPG cylinder for the heater. Most drivers have no idea they are moving dangerous goods - but ADR does not care about ignorance, and the petrol in the back is Class 3 flammable liquid the moment the wheels turn. The good news buried in HSE’s carriage of dangerous goods manual is a set of exemptions designed for exactly this scale of carriage. The bad news is that “exempt” has edges, and plenty of businesses sit outside them without knowing.
The first exemption people reach for is private use of vehicles - the rule that lets you drive home from the petrol station with a can for the lawnmower. HSE’s manual notes an important sharpening: there are now limits on the total quantity that may be carried under this exemption, and other legislation may separately limit carriage of petrol. The CDG Regulations add their own limits for private carriage of explosives. The operational message: private use means private. The moment the fuel is for the business - the works generator, the hired kit, the job - you are in commercial carriage, and this exemption is not your cover.
For commercial carriage, the working tool is the small load exemption in ADR 1.1.3.6, and HSE’s manual walks through its mechanics carefully. The logic runs on transport units and transport categories. The quantity that matters is the total dangerous goods carried in packages by the transport unit - usually the van or lorry, including any trailer it pulls. Every substance is assigned a transport category, given in column 15 of Table A in ADR chapter 3.2 (with a fallback table at 1.1.3.6.3), and each category has a load threshold.
Two rules catch people immediately. Small load exemptions do not apply to tankers or bulk carriage - this is a packaged-goods regime. And the maths is per transport unit: what is in the trailer counts toward the same threshold as what is in the van.
HSE’s worked example makes it concrete: LPG sits in transport category 2 with a small load threshold of 333kg, and with no limited-quantity provision applying, all cylinders count toward the limit. Below 333kg, the minimum ADR requirements apply; above it, the full weight of the regulations lands.
This is the subtlety that separates operators who are legal from operators who are lucky. If a vehicle is carrying under the small load threshold, many of ADR’s requirements fall away - but, as HSE puts it, “what is not exempted is still required”. The manual notes that some care is needed here, and lists the kind of obligations that typically remain even for small loads. The remaining requirements are the everyday discipline: packages properly secured, the load sensibly stowed, containers that are fit for purpose and closed, basic fire precautions. A leaking jerry can loose in the footwell is not “under the threshold” - it is a breach of the parts of ADR that never switch off.
The most common error is assuming all fuels share one threshold. They do not. Transport category varies by substance and hazard, which is why the manual insists on checking column 15 of Table A rather than assuming. Mixed loads - petrol cans plus LPG cylinders plus paint - each contribute against their own category’s arithmetic, and the combined calculation can push a plausible-looking load over a threshold the driver never checked. The manual’s derogation-amended table helps, but HSE warns it needs to be used with care.
For most service fleets the compliance shape is simple once seen: list what actually travels in the vehicles - fuels, gases, solvents, aerosols - find each substance’s transport category, do the transport-unit arithmetic, and work out whether the fleet sits under the small load thresholds. Under: document the calculation, and enforce the always-on rules - securing, stowage, container condition, fire discipline. Over: the vehicle needs the fuller regime, and that decision belongs in writing with the DGSA or competent adviser, not in a driver’s head.
The roadside reality is that an examiner who opens a van and finds loose fuel cans will not start from “probably exempt” - they will start from “dangerous goods in packages” and work backward. The operator who can produce the category calculation and show the load discipline is having a five-minute conversation. The operator shrugging is having a longer one.
Fuel carriage sits in the blind spot between “obviously dangerous goods work” and “just a can in the back”. ADR drew the line long ago; the small load exemptions simply decide which side of it your Tuesday morning van is on.