Heavy-Haul Routes and Construction Access for Data Centers

Most of what goes into a data center arrives on ordinary trucks. The exception is the high-voltage substation, whose main power transformers are among the heaviest objects that travel on public roads. The Department of Energy describes a large power transformer, generally one rated 100 MVA or more, as weighing approximately 100 to 400 tons, or 200,000 to 800,000 pounds.¹ The federally mandated maximum on the Interstate System is 80,000 pounds gross vehicle weight.²

That gap is why a parcel can be strong on power and land yet hard to build. If the only road in crosses an old bridge, a low rail underpass or a tight intersection, the transformer delivery may need a long detour, temporary works or a road improvement that involves the state, the county and sometimes a railroad. The cost is not trivial even when it works: utilities told GAO that large power transformers can cost as much as $10 million to buy and hundreds of thousands of dollars to move.⁵

The site access guide covers legal access, frontage and entrances. This guide covers the route beyond the property line: what heavy loads need, how they are permitted and how construction traffic is managed over a multi-year build.

Federal law sets the baseline: 80,000 pounds gross, 20,000 pounds on a single axle and 34,000 pounds on a tandem axle, on the Interstate System and reasonable access to it. The federal government does not issue oversize or overweight permits; permitting is a state option, and for nondivisible loads, states may issue permits without regard to the axle, gross or bridge formula limits.² A transformer is the textbook nondivisible load.

Each state draws its own lines. Texas is a useful example because its rules are published in detail. TxDMV issues a superheavy single-trip permit for nondivisible loads over 254,300 pounds gross, loads over the maximum permit weight on any axle or axle group, or loads between 200,001 and 254,300 pounds with less than 95 feet of axle spacing.⁶ Separately, loads over 20 feet wide, 18 feet 11 inches high or 125 feet long need a route inspection certification on file before a permit is issued.¹¹

Rules differ from state to state, and a route that crosses a state line needs a permit in each. Confirm current limits with the state DOT or motor carrier agency for the actual route.

Weight is a bridge problem first. TxDOT’s bridge manual says a superheavy load requires structural evaluation of individual bridges on the proposed route, reviewed by TxDMV and TxDOT’s Bridge Division. For any bridge with a deck, superstructure or substructure condition rating of 4 or less, the reviewer is told to read the actual written inspection record.³ Bridges that fail can sometimes be crossed with temporary measures or avoided by rerouting; occasionally there is no practical route.

Size matters as much as weight. Reported moves in Greene County, Ohio, carried transformers from a railroad site to a substation about eight miles away. One unit weighed about 369,400 pounds; loaded, the rig was about 145 feet long and nearly 20 feet high, too tall to pass under interstate and U.S. 35 bridges, so crews raised power lines and turned signals along a surface route under rolling road closures.⁸ Loads like that also need clearance under signals and overhead wires, turning room at intersections and a stable surface into the site.

For screening, the practical test is the last 5 to 20 miles: which roads connect the site to a state highway or rail point, what bridges and crossings lie on them and whether there is more than one option. Grade matters too, which is one more reason to look at topographic data early.

Rail carries many large transformers most of the way. The heaviest units ride on Schnabel cars, specialized railcars that suspend the load between two halves of the car; Trains magazine describes capacities of roughly 392 to 523 tons depending on configuration, three to five times the capacity of a modern freight car.⁷ The Ohio moves above started at a railroad site in Fairborn, with the road leg only covering the final miles.⁸

For a site, that means a usable rail point within reasonable road distance can matter more than a spur onto the property. A dedicated spur is a bigger commitment. Iowa DOT’s rail tool kit notes that a simple stub-in spur limits how many cars can be handled at once, while a runaround or siding allows more flexible operations, and that Class I railroads may require loop tracks for a connection to a main line.¹² Iowa law lets a railroad require the party being served to pay for right-of-way and construction of a spur, with the estimated cost deposited before the railroad incurs expense.¹³ Other states and railroads set their own terms.

Heavy-haul moves are a handful of days. Construction traffic lasts years. Large campuses bring a steady stream of aggregate, concrete, steel and equipment, plus a workforce that arrives and leaves at the same hours. Meta’s campus in Richland Parish, Louisiana, is the clearest public example. A November 2025 investigation reported that thousands of dump trucks and 18-wheelers were passing through the small town of Holly Ridge every day, that crashes on roads around the site had risen more than 600% (at least 64 by September 2025, against nine the year before), and that the elementary school at the junction of Highways 80 and 183 had closed a playground beside the road.⁹ WWNO reported in July 2026 that construction employment could reach about 7,500 workers.¹⁴

Phased campuses stretch the effect. Officials in Caddo Parish, Louisiana, expect heavy trucks on parish roads for about five to seven years as a large data center is built in phases.¹⁰ Many jurisdictions will require a traffic impact study and may condition approval on turn lanes, signals or widening, which affects both cost and the construction schedule.

Rural roads are often not built for sustained heavy truck volumes, and damage has become a common local complaint. Counties are responding with road use and maintenance agreements. In Ozaukee County, Wisconsin, an agreement with the City of Port Washington has the county highway department repair and maintain roads in and around a Vantage Data Centers campus and bill the company monthly for time and materials; either party can end the arrangement on 60 days’ notice.⁴ Caddo Parish officials have said the developer of a planned campus will be held responsible if construction causes significant roadway damage.¹⁰

Terms vary widely. Points worth settling in an agreement or permit conditions include:

• Designated haul routes and any roads closed to construction trucks
• A documented condition survey of those roads before and after construction
• Who repairs damage, how fast, and how costs are billed or bonded
• Hours of hauling, school-zone limits and dust and debris control
• Permanent improvements the project funds, such as turn lanes or resurfacing

For a landowner or developer, an agreement is usually better than an open dispute. It sets expectations early and gives the county a reason to support the project. Confirm the specific terms with the county engineer and counsel.

1. 01Identify the nearest state highway and the nearest rail point that could offload a transformer, and map every road between them and the site.
2. 02List the bridges, rail crossings, underpasses and overhead lines on each candidate route, and note posted limits.
3. 03Ask the state DOT or permit office what review a superheavy load on that route would trigger.
4. 04Ask the utility where its transformers would ship from and how it has delivered to nearby substations. Equipment timing is covered in transformer and switchgear lead times.
5. 05Estimate construction traffic and talk to the county about haul routes and a road use agreement before rezoning, not after.
6. 06If rail matters, contact the railroad early about service, spur design and cost-sharing.

Access is one part of the screen we run on power, land and entitlements; our methodology explains how it fits with substation capacity and proximity. If a parcel looks strong but its roads are uncertain, get a site reviewed before committing to engineering studies.