A standard US truck scale deck measures 10–12 ft wide (3.05–3.66 m), with 11 ft (3.35 m) cited as the most common configuration for general commercial weighing, and 90% of installed decks falling inside the 10–12 ft band [S2][S3].
Texas size-and-weight rules measure width between the outside points of the widest extremities, excluding safety devices, and the maximum legal load width is 8.5 ft (2.59 m) before an oversize permit is required [S1][S6]. A truck that legally runs at 8.5 ft still needs room to steer, which is where the 3.0 m vs 3.4 m deck choice starts to matter on the ground.
Why 3 m vs 3.4 m Is the Real Decision, Not 10 ft vs 11 ft
Manufacturer literature typically quotes widths in feet, but the engineering decision is between 3.0 m (≈10 ft) and 3.4 m (≈11 ft) decks, with 3.66 m (12 ft) and 4.27 m (14 ft) reserved for busier or special-purpose sites [S3][S4]. The 3.0 m deck leaves about 1.5 ft of total extra space on either side of an 8.5 ft vehicle; the 3.4 m deck leaves about 2.5 ft; a 12 ft (3.66 m) deck leaves about 3.5 ft [S3]. That extra 1 ft of deck is the entire reason the wider platform exists for wide loads and oversize vehicles.
For comparison, full-length truck scales span 18–36 m (60–120 ft) in length and 3–4 m in width, so width choices in the 3.0–3.4 m range are a tight sub-set of the standard envelope rather than a custom build [S5]. Some manufacturers list 3 m and 3.2 m as standard optional widths, with custom widths available, which is why 3.4 m shows up as a special order rather than a catalog default at certain vendors [S7].
When a 3.0 m Deck Is the Right Pick
A 3.0 m (10 ft) deck is a practical configuration when the site mainly handles standard commercial trucks and the approach road is straight [S3]. It uses less site footprint, which matters at older factories or plants where the scale has to be dropped into an existing traffic route between buildings, gatehouses, or loading bays [S3].
Typical applications: a 10 ft × 60 ft or 10 ft × 70 ft truck scale, where the deck is long enough for the longest vehicle but the site has no room for extra width, and traffic is low enough that drivers can afford to slow down or stop if they approach slightly off-center [S3]. For low-traffic operations (a few trucks per day, all conventional tractor-trailers or dump trucks running legal 8.5 ft width), the 1.5 ft of total extra space is workable, and the savings on foundation, approach slabs, and civils are real [S3][S4].
Standard US legal width is 8.5 ft; if every vehicle running across the scale is at or below that, the 3.0 m deck does not constrain the operation, and the wider deck is essentially buying unused clearance [S1][S6].
When 3.4 m Starts to Pay for Itself
A 3.4 m (11 ft) deck is the most commonly specified width for general commercial truck weighing, and is described as the "sensible balance" between site space and driver room for factories, warehouses, grain facilities, and logistics yards [S3]. It is also the deck length most often listed as the default in manufacturer literature for standard highway truck weighing, appearing in standard sizes like 11 ft × 60 ft and 11 ft × 70 ft [S2][S3].
Where 3.4 m clearly wins over 3.0 m: any site regularly handling wide loads, oversize vehicles, or trucks that have just turned or backed out of a loading area and need to correct steering before all axles are fully on the platform. The extra foot of deck gives the driver the room to straighten out without stopping, which on a high-cycle site (dozens to hundreds of trucks per day) becomes a measurable throughput difference, not a comfort one [S3].
Advance-scale guidance also splits truck scales by duty cycle: static (vehicle halts completely for a precise weight check) vs Weigh-In-Motion (WIM) where the vehicle does not stop, and WIM sites with off-axis approach trajectories benefit even more from the wider deck [S8].
Decision Matrix: 3.0 m vs 3.4 m vs Wider
Lining the options up against the criteria that actually drive the spec:
1. Vehicle mix. Standard 8.5 ft trucks only: 3.0 m is sufficient. Mixed fleet with regular oversize or wide-load moves: 3.4 m. Heavy or special-purpose vehicles (agricultural, mining, military, modular homes): 3.66 m (12 ft) or 4.27 m (14 ft) [S3][S6].
2. Approach geometry. Straight, open approach with no nearby turns: 3.0 m works. Approach immediately after a turn, gate, or loading bay: 3.4 m, because drivers need room to correct steering before all axles are positioned on the platform [S3].
3. Daily cycle count. Low volume, a handful of trucks per day: 3.0 m is acceptable. High volume, dozens to hundreds of trucks per day, the extra foot of deck is a throughput asset, not a cost [S3].
4. Site footprint and civils cost. 3.0 m is the cheapest foundation, smallest approach slab, easiest to retrofit into an existing yard. 3.4 m adds about 13% more deck area in the width direction, which propagates into longer approach slabs and wider pier spacing. Beyond 3.4 m, costs step up further and lead times extend because widths above 11 ft are typically custom or special-order rather than catalog standard [S3][S7].
5. Future fleet change. A well-made truck scale can last 10–20 years, so the deck width should be sized for the largest vehicle the site expects over the deck's service life, not just today's fleet [S4]. If a 3.0 m deck is sized for current trucks but oversize moves are planned within the next decade, 3.4 m is the cheaper long-term call.
Limits, Failure Modes, and What Wide Loads Actually Need
Width is not the only constraint. Texas oversize rules also enforce gross vehicle weight, axle limits (e.g. 23,000 lb on a single axle, 46,000 lb on a tandem axle for ready-mixed concrete trucks), and per-vehicle commodity exceptions (timber, poles, milk, ready-mix), all of which interact with the deck length and capacity, not just the deck width [S1].
A 3.4 m deck does not, by itself, let a wide load be weighed legally, because width is measured at the vehicle, not the scale, and loads above 8.5 ft still require an oversize permit, escorts, and route approval, independent of scale selection [S1][S6]. The wider deck only addresses the maneuverability of a vehicle that is itself at or near the legal width limit.
For weighbridge engineering fundamentals, including deck-to-foundation ratios and typical 10–20 year service life assumptions, the truck scale reference covers the long-form spec background. Sites that also run dump truck or concrete mixer truck fleets should cross-check deck length against the longest commodity vehicle, not just the longest highway tractor-trailer, because concrete mixers and dump trucks can run at very different axle spacings.
Sourcing, Standards, and Trackable Signals
Width measurement methodology is defined regulator-side: Texas measures from the outside points of the widest extremities, excluding safety devices, and the 8.5 ft legal-width threshold is the same reference point used by oversize permitting [S1][S6]. On the manufacturer side, the 10–12 ft (3.05–3.66 m) width envelope is consistent across at least four independent US and international references, with 11 ft (3.35 m) as the modal default [S2][S3][S4][S5].
Two trackable signals to watch: (1) whether a given site files oversize permits at a rate that justifies 3.4 m, which can be checked against state DOT permit volumes; (2) whether the largest vehicle expected over the next 10–20 year service life of the deck is wider than today's fleet, because the truck scale deck width is a 10–20 year commitment, not a 2-year one [S4].
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