Michigan truck weight limits
On Interstate highways in Michigan, federal weight limits apply. Four checks decide whether your truck is legal — and the one that surprises most drivers is the Federal Bridge Formula, which can fail a truck that passes every other limit.
Federal limits on Michigan Interstates
| Limit | Maximum | Applies to |
|---|---|---|
| Single axle | 20,000 lb | Any one axle |
| Tandem axle group | 34,000 lb | Axles 40–96 inches apart |
| Tridem axle group | governed by the bridge formula | 3 axles in a group (no flat federal cap) |
| Gross vehicle weight | 80,000 lb | The whole rig |
| Bridge formula | varies by spacing | Every group of 2+ axles |
The bridge formula check
L is the spacing in feet between the outer axles of a group, N the number of axles. A standard 5-axle rig at 51 ft is capped at 79,500 lb by this formula — under the 80,000 lb gross limit. Full explanation with worked examples.
Michigan-specific rules
Michigan is the highest-GVW state in the country — but not the way most people think. On the Interstate system, standard federal limits apply: 20,000 lb single axle, 34,000 lb tandem, 80,000 lb gross, plus the Federal Bridge Formula. Michigan's famous 164,000 lb trucks run on non-Interstate state trunklines and local roads, reached not by allowing heavy axles but by spreading the load across up to 11 axles under a spacing-based per-axle cap. A rig can be perfectly legal in Michigan and grossly illegal the moment it enters an Interstate — the axle count is the whole game.
Michigan exceptions to the federal limits
Michigan caps per-axle load by axle spacing (MCL 257.722), not with the flat federal single/tandem numbers, on non-Interstate roads:
| Axle spacing | Max load per axle (normal loading) |
|---|---|
| 9 ft or more apart | 18,000 lb |
| 3½ – 9 ft apart | 13,000 lb |
| Less than 3½ ft apart | 9,000 lb |
- Maximum gross weight: 164,000 lb, with a maximum of 11 axles.
- On designated highways (bridges and pavement rated for it), MDOT or local authorities may allow tandem axle assemblies up to 16,000 lb per axle.
- On Interstates, federal limits govern — 20,000 lb single / 34,000 lb tandem / 80,000 lb gross, plus the bridge formula.
Seasonal & designated-route rules in Michigan
Michigan enforces seasonal ("frost law") weight restrictions, typically from late February into April or May, when thawing weakens roadbeds. On routes posted as seasonal, loads are cut by 25% on rigid (concrete) pavement and 35% on flexible (asphalt) pavement. MDOT sets start and end dates by measuring frost depth, and restrictions lift region by region as roads recover. Always check MDOT's current posting before running heavy in spring.
Overweight permits in Michigan
Loads over the legal limits need an oversize/overweight permit from MDOT (single-trip or annual, issued by route). Permits are route-specific because bridge and pavement ratings vary — a load legal on one trunkline may be denied on another.
Fines & enforcement in Michigan
Enforced by the Michigan State Police Motor Carrier Division at fixed scales and with portable enforcement. Overweight loads are fined on an escalating, per-pound-over-the-limit basis, so a large overage gets expensive fast; serious violations can put a vehicle out of service.
What dispatchers should check in Michigan
- Interstate vs. non-Interstate routing — any Interstate mileage caps you at 80,000 lb gross / 34,000 lb tandem, not Michigan's higher limits.
- Axle count and spacing — Michigan's high GVW only works with enough axles at the right spacing; check per-axle loads against the spacing table above.
- Designated-highway status — the 16,000 lb tandem applies only on specifically designated routes.
- Season — check MDOT's current frost-law postings (Feb–May) before committing a heavy load.
Michigan truck weight — frequently asked questions
How much can a truck weigh in Michigan?
On Michigan Interstates the federal gross-weight limit is 80,000 lb, with a 20,000 lb single-axle limit, a 34,000 lb tandem limit and the Federal Bridge Formula. Michigan sets its own limits on non-Interstate roads — see the Michigan-specific rules on this page.
Does Michigan follow federal truck weight limits?
On the Interstate system, yes — federal limits govern in every state. Off the Interstate, Michigan applies its own axle, gross and permit rules, detailed on this page where they have been verified against the official state source.
What is the single-axle weight limit in Michigan?
The federal single-axle limit of 20,000 lb applies on Michigan Interstates. Some states set a different single-axle figure on non-Interstate roads — check the Michigan-specific section above for the governing number.
What is the maximum tandem-axle weight in Michigan?
On Michigan Interstates the federal tandem limit is 34,000 lb. Several states allow a different tandem weight on non-Interstate roads — see the Michigan exceptions above for the figure that governs.
Scaled heavy in Michigan?
If the trailer tandems are over, the fix is usually a computed tandem slide, not unloading — see how sliding tandems shifts weight. And here's what an overweight ticket really costs before you decide to run it.
Run your scale-ticket weights through the federal and bridge-formula calculator in your browser. The full platform predicts axle loads from load placement before you load, computes the exact slide-to-legal fix, and applies Michigan rules on top of the federal baseline.
Open the free calculatorOur calculator runs the federal single, tandem, gross and Bridge Formula checks in seconds. The full platform adds per-state limits, axle-load prediction and the slide-to-legal fix.
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