Truck & Car Guides / Reference
Truck and car FAQ
Quick answers to the most common questions about trucks, trucking careers and everyday cars, from how much a semi weighs to how old you must be to drive one.
These are the questions we hear most. Each answer is short, with a link to the full guide. Rules change and vary by state, so always check the official sources such as the FMCSA and your state DMV.
Trucks
How much does a semi truck weigh? An empty tractor and trailer together often weigh somewhere around 30,000 to 35,000 pounds, depending on equipment. The federal gross weight limit on the Interstate system is generally 80,000 pounds without a special permit. See weight limits and the bridge formula.
How long is a typical tractor-trailer? A common US setup pairs a tractor with a 53-foot trailer, for an overall length of roughly 70 to 80 feet depending on the tractor. See semi truck anatomy.
Why do trucks have so many wheels? More axles spread the weight, protecting roads and bridges and allowing heavier legal loads. A standard rig has five axles and 18 wheels, which is where the name "18-wheeler" comes from.
How do air brakes work? Compressed air holds powerful spring brakes off and applies the service brakes when the driver presses the pedal. If air is lost, the spring brakes apply. See air brakes.
What is that loud rattling noise trucks make when slowing? That is usually an engine brake, often called a jake brake. Some towns restrict its use. See jake brakes.
Becoming a truck driver
How old do you have to be? In most states you can get a CDL at 18 for driving within your state (intrastate). Federal rules require drivers to be at least 21 to drive commercial vehicles across state lines (interstate), apart from limited pilot programs. See CDL classes.
Do I need to go to school? Since February 7, 2022, federal Entry-Level Driver Training (ELDT) rules require new Class A and Class B applicants, and those seeking certain endorsements, to complete training from a provider listed on the FMCSA Training Provider Registry before taking the skills test.
How many hours can a truck driver drive? Property-carrying drivers may drive up to 11 hours within a 14-hour on-duty window after 10 consecutive hours off duty, with a 30-minute break required after 8 cumulative hours of driving, plus weekly limits. See hours of service.
What is an ELD? An electronic logging device records driving time automatically for hours of service. See ELDs.
How are truck drivers paid? Commonly by the mile, by the hour, as a percentage of the load, or a combination. See life and pay models.
Safety
Where are a truck's blind spots? Directly in front, directly behind, and along both sides, especially the right. See sharing the road.
How long does it take a truck to stop? Far longer than a car, especially when loaded and at highway speed. See stopping distances.
What are runaway truck ramps for? They stop trucks whose brakes have failed on steep downgrades. See runaway truck ramps.
Cars
How often should I change my oil? Follow your owner's manual or the car's maintenance minder; intervals vary widely by engine and oil type. See maintenance and warning lights.
Is an EV or hybrid right for me? It depends on charging access, driving distance and budget. See EV vs hybrid vs gas.
What does a flashing check engine light mean? Often a severe misfire. Reduce speed and get it checked right away.
Look up unfamiliar terms in the trucker glossary, and use the pre-trip inspection checklist as a study aid.
