what is the purpose of weigh scales on the interstate/highways
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Heavier vehicles end up damaging the road. The weigh stations are there to ensure freight trucks aren’t overweight.
To make sure trucks aren’t carrying too much weight. Overloaded trucks can damage roads and cause accidents.
Commercial drivers have strict regulations that they need to follow to operate . It’s not just a matter of weight, but the weight has to be appropriately distributed between each axle. The wheel assemblies on trailers are specially designed so that they can slide forward or back, giving a balance between safe weight distribution for hauling or a better position for maneuvering in tight city spaces
Additionally, drivers are ultimately responsible for inspecting their vehicles for safety issues and keeping a log of their working hours. These logs and additionally safety inspections were checked at the weigh stations as well using a random method. This is part of why you see some drivers keeping their trucks cleaner than others–a clean truck is a sign of a well maintained truck, and there’s less chance of them having to submit to a random inspection.
Add: Some states also use them as environmental inspections for agricultural pests, prevent invasive water species on watercraft, or other invasive terrors like the spotted lanternfly.
Former truck driver here:
Weigh scales are for what their name implies: to weigh trucks. every set of axles on a truck and in a trailer has a legally mandated maximum weight they can carry.
On a trailer the axles can move backwards and foreards by a few feet to distribute the weight a bit better. This also affects trailer turning but is not important foe this discussion.
Weigh stations ALSO are staffed by highway officers who, can perform inspections on trucks to ensure that they meet highway safety requirements.
If they see a truck that is overweight, or has lights that do not work they might suspect the driver has other violations such as poor tire conditions, or log book violations.
For safety truck drivers has strict rules about how long they can drive, and how long they can “work” which involves other tasks that do not involve driving, such ad loading or unloading or waiting at border crossings.
Trucks are massive vehicles, and when accidents happen involving trucks many people can easily be hurt and killed ao its imperative that trucking companies and their drivers be held to strict standards.
It’s been decades since I’ve seen one of these open in Texas. Are they open more often in other states?
To make sure trucks are not overweight, but also that the weight distribution is balanced properly. Too much total weight, or too much weight on a specific tire, will cause more wear and tear on the roads.
To see if commercial vehicles are overweight. But the bigger purpose they serve is inspections. Which is honestly bullshit because it all depends on the mood they’re in. If you asked me to find discrepancies on a truck fresh off the assembly line, I could do it every single time.
The underlying reason is revenue. Sure, there are weight limits that bridges and roads are built to withstand tho.
In order to prevent excessive wear on highways, there are regulations about how much trucks can carry based on their wheel count, etc.
For truckers, there is an incentive to carry more on each haul to make more money on each run. So they might be tempted to overload the truck to eek out a few extra dollars.
Weigh stations are there to keep them honest with random checks.
Think of yourself standing on a wooden platform. The plywood, the 2x4s, and even the nails holding it together all have a rating for how much weight they can support. Now think of a treadmill- same thing, except you are moving with footfalls striking the platform with every step- your entire weight plus the momentum of you falling on your one foot: running is just controlled falling. So while your weight might be 200lbs, what’s really happening is 25lbs per square inch of your foot (just making up numbers here) hitting the conveyor belt with each step. Considering it would be completely catastrophic for both you and the treadmill if your foot was at 100lbs per square inch(going through the conveyor into the floor) they’ve engineered this particular treadmill to withstand 50lbs per square inch: more than enough wiggle room to make aure all that happens isyou complete your workout.
Tires are the shoes, and the axles are the feet of a vehicle. An engineer has calculated how much weight goes through the square inches that are actually in contact with the road surface, and they have determined that the max vehicle weight is 80,000lbs. More specifically, 12,000 for the front two tires, and 34,000 /8 for the other sets of tires. Those weigh stations measure each of those 3 sets of tires to make sure all are in compliance.
It is possible to get permits for other tire configurations: someone can engineer a set of 40 tires on a trailer to support a heavier load. A truck can also have two sets of steering tires. This is still more likely to cause additional wear on the road, and the fees mitigate that risk to the state.
In Idaho, it’s not just the weight. There are roads there with hairpins that a standard semi truck could not successfully negotiate with the tandems all the way back. The permit to operate there requires the driver calculate the tightest turn the truck can make, and they are restricted to certain roads if that turn is wider than what they’ve built in the mountains there.
Most states operate their weigh stations only upon entering the state: the main concern on the interstates is interstate travel. Police have the authority to pull over and weigh any truck, though: highway patrol has portable scales in the trunk.
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