The curtain on a curtain-sider is not a load restraint device. It says so in DVSA's own guidance, but I've seen drivers treat the curtain like it's doing a job it isn't designed to do — stacking pallets tightly against the sidewall, pulling the curtain across, and calling it secured.
DVSA pulled me into a check site on the M6 northbound in 2019, about four miles north of Knutsford. The examiner asked me to open the nearside curtain. I had eight pallets of mixed consumables, all plastic-wrapped, stacked two high, three lashings across the load — single-point anchors, nothing calculated, done by feel. He looked at it for about forty seconds and said, 'I'm going to issue a PG9.'
I didn't argue. He was right. What I had was pallets that would have moved under emergency braking. Not collapsed — moved. That movement is the problem. A pallet shifting six inches into the curtain rail on a motorway braking event can be catastrophic. The PG9 wasn't the worst outcome of that day.
What the law actually says about load restraint
The Road Vehicles (Construction and Use) Regulations 1986 require that loads are secured so they cannot fall from the vehicle or move in a way that could cause danger. That's the baseline. Short, vague, hard to argue against from the enforcement side. What it doesn't do is tell you how many lashings you need.
The calculation standard that DVSA enforcement officers use when a load has shifted or looks inadequately secured is BS EN 12195-1:2010 — Load restraining on road vehicles, Safety, Part 1: Calculation of securing forces. This is a European standard retained in UK law and accepted by enforcement agencies as the method for determining whether load restraint is adequate.
The standard isn't law in the sense that you won't be prosecuted for not knowing the formula. But if you end up at a public inquiry after a load shift incident, 'I used EN 12195-1 to calculate my lashing requirement' is a defence that works. 'I tightened the straps until they felt right' is not.
The force thresholds you're working to
The basics from the calculation standard: your load restraint system must be able to withstand forces equivalent to the entire weight of the load in the forward direction. Half the weight of the load laterally — to each side. Half the weight of the load to the rear.
So on a 20-tonne load: 20 tonnes of restraint capacity forward, 10 tonnes lateral each side, 10 tonnes rearward. That sounds like a lot of lashing. It is, if you're relying on tie-down lashings alone. It's much less if the load is also blocked and braced, or if there's a physical barrier between the load and the headboard.
The standard uses a friction coefficient to account for the fact that load-to-vehicle contact provides some resistance. If you don't know the specific friction coefficient for the load and vehicle bed combination — and most of us don't — the standard specifies using 0.2 as the default. That's low. Rough timber on a flatbed might actually achieve 0.4 or higher, but you can't claim it without evidence. The default is 0.2 and you work from there.
Changing the friction coefficient by using anti-slip mats is one of the most effective things you can do to reduce lashing count. An anti-slip mat with a certified coefficient of 0.5 or higher, placed between load and vehicle floor, can halve the number of lashings you need. That's not a trick — it's physics. And it's why DVSA guidance explicitly mentions anti-slip matting as a legitimate load securing method.
Curtain-siders specifically
Curtain-siders are the most commonly stopped vehicle type for load security issues in the UK. Not because drivers on curtain-siders are worse at load restraint — it's because the curtain-sider design makes the problem invisible until an examiner opens the curtain, and the temptation is to let the curtain do the work.
The curtain is designed to keep weather and debris out. It's not rated to restrain cargo. On a correctly secured curtain-sider load, opening the curtain should reveal lashings over and around the cargo that hold it in position regardless of whether the curtain is there or not. If the lashings you have wouldn't hold the load with the curtain removed, the curtain isn't fixing that problem.
I've seen DVSA examiners at Stafford Services open a curtain and watch the load shift visibly when the curtain comes back. No emergency braking required. The pallets moved three inches just from the curtain pressure releasing. That vehicle went nowhere until the load was re-palletised, restacked and properly lashed. Hour and a half wait on the hard shoulder while that happened. Then the PG9 paperwork on top.
Types of lashing and which the standard uses
There are four main methods under EN 12195-1: tie-down lashing, direct lashing (over and through the load), blocking and bracing, and friction-based restraint using anti-slip surfaces.
Tie-down lashing is the one most people use — ratchet straps or chain over the top of the load, pulling it down and generating friction between the load and the vehicle floor. The calculation for this method relies heavily on the lashing angle — straps at a low angle to the horizontal generate less useful downward force than straps running more steeply. A strap that runs almost horizontally across a flat load on a low-sided trailer is doing almost nothing useful in the lateral or forward direction.
Direct lashing — attaching straps directly to the load itself and anchoring them to the vehicle — is more efficient where the load has attachment points. A machine on a flatbed with lifting eyes can be directly lashed; that's a far more reliable method than trying to achieve restraint through friction alone on a slippery pallet base.
The lashing straps themselves need to meet BS EN 12195-2 for webbing straps, with appropriate lashing capacity for the forces involved. The rated capacity of the strap needs to match what EN 12195-1 tells you you're asking of it. If you're using straps that are too lightweight for the load weight and method, the calculation doesn't work even if the strap count is right.
What DVSA is actually looking at
When an examiner opens the curtain or looks at an open flatbed, they're asking three questions. First: is there obvious load movement potential — can the load shift under normal driving conditions without the restraint resisting it? Second: is the restraint method plausible — are the lashings attached to the load and the vehicle in a way that could reasonably be expected to work? Third: are the lashings in good condition and appropriate for the load?
They're not running EN 12195-1 calculations at the roadside. But if the load looks inadequately restrained and a serious event occurs — or if the case ends up being argued — the standard is what gets applied retrospectively. 'I used the standard and my lashing count was sufficient' is what you want to be able to say. 'I used three straps and they felt tight' is not.
Examiners also look at lashing condition. Straps with cuts, fraying, bleached webbing, or missing labels showing the rated capacity are not acceptable as load restraint. DVSA can prohibit a vehicle for defective lashing equipment. Keep a log of strap inspections if you're an owner-driver — the way you keep a log of walkaround checks. A strap used repeatedly on rough loads has a service life.
The driver's role vs the loader's role
The loader or shipper is responsible for stacking and securing cargo before the driver takes over. But the driver is responsible for the load from the moment they take the vehicle. You sign for the condition of the load when you depart. If the load is not adequately secured when you arrive at the shipper, you can refuse to take it.
That sounds straightforward. In practice, at a busy distribution centre at two in the morning, pushing back on a load security issue takes nerve. I've done it. The person responsible for the bay told me it was fine and they'd done it a hundred times. I told them the strap count was wrong and I wasn't leaving until it was fixed. I waited forty-five minutes. Then I left, with a correctly lashed load, and a memo to the TM explaining why the departure was late.
The TM backed me. Not every TM does. But if that load had shifted on the M6 and an examiner had issued a PG9, the late departure would have been a much smaller problem than the one I'd have been dealing with instead.
Practical checklist before you pull the curtain closed
You can't run EN 12195-1 calculations in the bay at two in the morning — not without training and the data to hand. What you can do is run a basic sense check. Is the load stacked stable and as low as possible? Is each unit properly secured to its pallet or directly to the vehicle where required? Are there anti-slip mats under pallets on a smooth aluminium floor? Are the straps rated for the load they're restraining? Are the strap angles steep enough to generate useful downward and lateral force?
And then: if the curtain wasn't there, would this load stay put under hard braking? If the honest answer is no, the curtain doesn't change that.
DVSA publishes guidance on securing loads on HGVs and goods vehicles at gov.uk. It covers curtain-siders, flatbeds, tippers, and specific load types. Worth reading once carefully, not because it covers every scenario, but because it tells you exactly what the examiner is working from.
If you're an owner-driver or running a small fleet and want to keep compliance visible in one place — driver hours, rest periods, WTD — ShiftOwt tracks EU 561 and WTD automatically for £5.99 a month. Load security compliance is a separate discipline, but the same principle applies: you want a record of what you checked and when, before someone asks you to prove it.