Types of trucks and semi-trailers: curtainsider, mega, low-bed, tanker, car carrier and reefer — specs, TIR approval and road weight limits from the EU to Central Asia

A trailer isn't picked by how big the job looks. It's picked by which of three things runs out first — weight, volume or deck space — and by whether the cargo needs a sealed box, an open deck, a tank or a temperature. Get that wrong and either the truck arrives half-empty on paper while full on the road, or it arrives legally overweight the moment it crosses a border with a lower ceiling than the one it left from.

This is a reference piece, in the same format as our guides to sea container types and railway wagon types — this time for the road leg of the Middle Corridor, from a European loading dock through Georgia to Central Asia and back. What each body type actually carries, what TIR approval physically requires on a curtainsider, and where the road's own weight limits stop matching the EU's the further east the truck goes.

Body types at a glance: what actually moves what

Nine body types cover almost everything that moves by road on this corridor. Three of them — curtainsider, mega and box — look similar from a distance and are chosen by very different logic; the rest are built around one specific cargo type and rarely substitute for each other.

Curtainsider and mega trailer: the two workhorses of general cargo

The curtainsider, or tautliner, is the default because it is the most flexible: side curtains open along the full length, so it can be loaded from either side or the back at almost any dock without a forklift approaching from a fixed direction. At roughly 13.6 by 2.48 by 2.6–2.7 metres internally, it carries about 24–25 tonnes and 90 cubic metres — enough for 33 standard EUR-pallets stacked once high, or fewer stacked higher if the cargo allows. For dense, palletised general cargo this is the combination that fills both limits — weight and volume — at close to the same point, which is exactly why it dominates the corridor.

The mega trailer solves one specific problem: cargo that runs out of space before it runs out of allowed weight. It shares the curtainsider's footprint but raises the internal height to about 3.0 metres instead of 2.7, which adds roughly 15% more volume — up to 100 cubic metres — without touching the axle configuration that sets the weight limit. Insulation material, furniture, empty packaging and other light, bulky freight are the classic mega loads; putting the same cargo in a standard curtainsider would leave weight capacity unused while the trailer is already visually full.

Box, flatbed, tanker, car carrier and reefer: the rest of the fleet

A box (dry van) trailer looks similar again but trades the curtain for rigid, lockable walls — no side access, one door at the rear. It costs some loading flexibility for real security and full weather sealing, which is what buyers with high-value or theft-sensitive cargo pay for. A flatbed or platform trailer goes the other way entirely: no walls or roof at all, an open deck usually rated for a load height of up to 2.5–3.0 metres from the ground, loaded from above or the side by crane. Steel coils, pipe, structural beams and construction materials that don't fit through a curtainsider's door opening go on a flatbed instead.

A tanker trailer is measured in litres, not pallets or cubic metres — a shell roughly 9.5 to 12.5 metres long commonly holding somewhere around 30,000 to 45,000 litres of fuel, chemicals or edible oil. A car carrier is measured in vehicles: a single-deck unit takes fewer, a double-deck rig — built up to about 4 metres combined height — typically carries somewhere around six to ten cars, which is the backbone of the used-vehicle re-export trade that genuinely moves through Georgia in volume. Both are single-purpose bodies that essentially never carry anything else.

A reefer trailer shares the curtainsider's rough footprint and volume but adds insulated walls and a diesel or electric refrigeration unit, holding a range from roughly −20°C up to +25°C; multi-temperature units split the box into two or three zones with movable bulkheads so frozen, chilled and ambient cargo can travel together. We've covered the reefer-versus-container decision for this corridor in detail elsewhere — reefer container vs reefer truck — so this piece treats the reefer trailer as one item in the fleet rather than repeating that comparison.

A tipper (dump) trailer, finally, self-unloads by tilting its bed — 30 to 80 cubic metres is typical, and heavy-duty multi-axle units built for off-road quarry and mine work can exceed standard road-legal weights entirely, which is why they mostly stay off the long-haul international leg and work short domestic routes instead.

Low-bed and lowboy: moving machinery and project cargo

None of the nine bodies above helps if the cargo itself is too tall, too wide or simply sits too high off the ground for a standard deck — which is what the low-bed exists to fix.

• Ground clearance is the whole point — a low-bed's deck sits in a dropped well 45 to 60 centimetres off the ground, roughly half a standard flatbed's height, buying back exactly the clearance that height-restricted cargo needs
• Deck length is modular — a standard low-bed deck runs 24 to 29 feet, and extendable ("stretch") versions reach roughly 50 feet for long items like wind-turbine blade sections or bridge girders
• The gooseneck usually detaches — a removable-gooseneck (RGN) low-bed lets the deck sit flat on the ground so tracked equipment can be driven straight on, rather than winched up a ramp
• Payload runs well past a curtainsider's — typical low-bed capacity is 25 to 35 tonnes, with specialised heavy units built for 60 tonnes and more
• Oversized permits are a separate document, not an option — anything exceeding standard width, height or length triggers a permit process in every country the load crosses, arranged well before the truck loads
• The classic cargo list is short and specific — excavators, cranes, transformers, wind-turbine components and heavy project cargo; general freight essentially never justifies the cost of a low-bed

Excavators, mobile cranes, transformers and other heavy equipment moving between Europe and Central Asia — including used machinery re-exported through Georgia — need exactly this profile: a deck low enough to keep the load's overall height street-legal, and a gooseneck that lets tracked equipment drive on rather than being craned or winched.

TIR approval: what makes a curtainsider legally sealed

A curtainsider crossing several borders on this corridor almost always needs a TIR carnet, and a TIR carnet only covers a vehicle that is itself TIR-approved — which is a specific, physical, inspectable status, not a paperwork formality layered on top of an ordinary trailer.

The requirement is straightforward to state and easy to get wrong in practice: the load compartment has to be built so nothing can be added, removed or substituted without either breaking a customs seal or leaving damage that is visible on inspection. That means sturdy walls, a curtain or tilt cover fixed down at points identified specifically for this purpose, and exactly one access point that can be sealed — not several openings that happen to be closed most of the time.

The approval itself is granted by a national authority, either to one individual trailer or, more commonly for standard production models, by type — a manufacturer type-approves a trailer design once, and every unit built to that design inherits the status without its own separate inspection. Either way the trailer travels with a Certificate of Approval, informally still called by its old form number in the trade, that a customs officer at any border checks against the physical vehicle before a seal goes on. A rectangular plate marked TIR, fixed front and rear, is the visible signal from a distance that this particular trailer is approved at all. None of this is permanent: certificates are re-inspected on a cycle of roughly two years, and any major repair to the load compartment — a new curtain, a rebuilt door frame — resets that clock, because the whole system depends on the physical trailer still matching what was inspected.

Road weight and axle limits along the corridor

A trailer built and sealed correctly for TIR transit still has to fit within a weight limit that changes country by country along this exact route, and the numbers are not the same all the way from Rotterdam to Tashkent.

The EU's own rule, Directive 96/53/EC, sets 40 tonnes as the standard gross combination weight and allows 44 tonnes specifically for combined transport — a truck carrying a loaded 40-foot ISO container, essentially — with a non-driven axle capped at 10 tonnes and a driven axle at 11.5. Türkiye's Road Transport Regulation mirrors this almost exactly: the same 10-tonne and 11.5-tonne single-axle figures, dual-axle groups scaled from 11.5 up to 18 tonnes depending on how far apart the axles sit, and the same 40/44-tonne gross-weight split. A truck loaded to European norms crosses into and across Türkiye without needing to think about the scale.

Georgia publishes a 40-tonne gross weight ceiling for international transport, alongside an 18.75-metre length limit and a 2.55-metre width limit — matching the EU's headline weight figure, even though a published per-axle breakdown wasn't found in this research, which is itself worth knowing: it means a forwarder should distribute a Georgian-bound load conservatively across the axles rather than assume the EU's specific 10/11.5-tonne split automatically applies.

The numbers change further east. Azerbaijan's published single-axle limit is 10 tonnes, in line with the EU and Türkiye, but its gross vehicle weight ceilings by axle configuration are reported at roughly 25 tonnes for a two-axle rigid truck, 36 tonnes for a four-axle configuration and 38 tonnes for a five-or-more-axle articulated combination — meaning the overall load a legal Azerbaijani configuration can carry sits two to six tonnes below the EU's 40–44 tonne ceiling, depending on how the axles are arranged. Kazakhstan runs a single-axle limit of 10 tonnes on national roads, but drops that to roughly 8 tonnes during the spring thaw, when meltwater weakens the pavement — a seasonal restriction none of the other countries on this corridor apply, and one that a spring load plan needs to account for explicitly. A change reported for 25 April 2026 would raise the allowance for some axle groupings, which is worth checking against current status before finalising a load plan rather than treating as settled. Uzbekistan's reported single-axle limit, 11.5 tonnes, sits closer to the EU and Turkish figures than either of its immediate corridor neighbours, though a discussed rise to 13 tonnes was not confirmed as in force.

Put the numbers side by side and the practical shape of the corridor becomes clear: the western half, EU through Türkiye and into Georgia, runs on essentially one weight standard; the eastern half, Azerbaijan and especially Kazakhstan, runs on a lower and in Kazakhstan's case seasonally variable one.

Why a fully loaded EU truck can become overweight east of Georgia

A truck loaded in Germany or Poland to the EU's 44-tonne combined-transport allowance, carrying a full 40-foot container on a fully weight-optimised chassis, is entirely legal from the loading dock through Türkiye and Georgia. The same truck, unchanged, can be over Azerbaijan's roughly 38-tonne articulated-combination ceiling the moment it crosses the border — not because anything was loaded incorrectly, but because the two countries simply set different ceilings for the same axle count.

This is exactly the kind of friction the corridor's own transit paperwork already runs into around the same geography — our piece on where a Europe-to-Central-Asia truck's paperwork runs out covers how common transit and the ECMT road-access quota both expire around Georgia and the Caspian, which is no coincidence: the same border zone where the customs cover changes is where the weight ceiling drops too. The practical fix is the same in both cases — plan the load to the tightest limit on the route rather than the most generous one, and treat Georgia as the point where the truck's paperwork and its weight plan both need rechecking before continuing east.

Choosing the right trailer for your cargo

• Start with what runs out first — weight or volume — a dense load (machinery parts, canned goods, liquids) hits the weight ceiling in a curtainsider long before the box looks full; a light one (insulation, empty packaging, textiles) fills the box first, which is the case for a mega trailer
• Match the body to the loading method the cargo actually needs — side-loaded pallets want a curtainsider, top-loaded steel wants a flatbed, tracked equipment wants a low-bed with a removable gooseneck
• Confirm the temperature requirement before booking, not after — a reefer trailer or a multi-temperature unit needs to be reserved specifically; it is not something a curtainsider can substitute for on short notice
• Check whether the shipment needs TIR — if it does, the specific physical trailer booked has to be TIR-approved, which rules out an ordinary uncertified curtainsider regardless of how well it would otherwise fit the load
• Size the load to the tightest country on the route, not the loosest — a truck built to the EU's 40–44 tonne ceiling can be overweight in Azerbaijan or Kazakhstan before it ever gets close to a Central Asian scale
• Plan the return leg from the start — an empty low-bed, tanker or car carrier heading back west earns nothing on the way home, which is exactly the problem we cover in finding a return load for a Europe–Central Asia truck

Road weight limits interact with how the cargo is loaded in the first place — a badly distributed load can be legal on total weight and still exceed a single axle's limit, which is one reason correct cargo securing matters as much for weight distribution as for keeping the load from shifting; a shipment carrying anything hazardous adds a further layer covered in our dangerous goods reference, since ADR classification affects which body type and which documents a load needs regardless of its weight.

Where the road leg fits next to rail wagons and sea containers

None of the nine road bodies above is the only way to move freight through Georgia — rail and sea each have their own equivalent reference. A curtainsider's dense-general-cargo role has a close rail counterpart in the boxcar and container flatcar covered in our railway wagon types piece, and a container that arrives by sea and needs to continue by road or rail is exactly the handoff our shipping container types reference describes from the maritime side. On the Middle Corridor specifically, cargo routinely changes mode at Poti or Batumi — arriving in a 40-foot container by sea or a fitting platform by rail, and continuing the last leg on a curtainsider or a chassis — so knowing all three reference tables together, road, rail and sea, is what actually lets a shipment be planned door to door rather than leg by leg.

Development prospects

The corridor's own infrastructure is being built to carry more of exactly this multi-modal traffic. Georgia's port investment programme — the new harbour crane at Poti lifting container capacity above 650,000 TEU by the end of 2026, and Anaklia's deep-water first phase due in 2029 — adds sea-side capacity that road hauliers already plan their onward legs around. Etihad Rail's freight expansion and the growth of the Baku-Tbilisi-Kars line both point the same direction: more containerised and palletised freight arriving by rail or sea and finishing its journey by curtainsider or flatbed, which keeps demand for standard road trailers growing even as rail and sea capacity itself expands.

The axle-weight gap between the EU and the corridor's eastern half is also unlikely to close on its own. Harmonising national weight limits requires bilateral or regional agreement, and Kazakhstan's own seasonal restriction is a physical response to road-surface conditions rather than a policy choice that treaty negotiation can simply remove. The realistic expectation is that a forwarder on this corridor will keep needing to plan around a lower ceiling east of Georgia for the foreseeable future, rather than assuming the gap disappears.

In short

Nine body types cover almost every cargo this corridor moves: curtainsider and mega for general cargo, box for security, flatbed and low-bed for open and oversized loads, tanker and car carrier for single-purpose freight, reefer for temperature, tipper for short-haul bulk. A curtainsider needs to be physically TIR-approved — sealed compartment, certificate, plate — before a carnet means anything for it, and a load built to the EU's 40–44 tonne allowance still needs rechecking against Azerbaijan's roughly 38-tonne ceiling and Kazakhstan's seasonal 8-tonne axle restriction before it clears the Caucasus. Tell us the cargo, the weight and the route, and we'll match it to the right body and the right country's limits before it loads.

See also: Types of shipping containers · Types of railway wagons · A truck from Europe to Central Asia: where the paperwork runs out · Finding a return load for a Europe–Central Asia truck · Dangerous goods: classes and documents · Packing and securing cargo