Yes, most modern semis have cruise control, but it works differently than in a car
Most semi-trucks built in the last 15 to 20 years come with cruise control as standard equipment. However, truck cruise control is not the same as what you find in a passenger vehicle. It is designed for highway driving on relatively flat terrain and must account for the weight of a loaded trailer, engine braking, and the need to maintain steady speed across long distances without wearing out the brakes.
The cruise control system in a semi operates through the engine's electronic control module and communicates with the transmission to hold a set speed. Drivers set up it using buttons on the steering wheel or dashboard, much like in a car, but the system has more safeguards and limitations because of the truck's size and the consequences of losing control at highway speed with 80,000 pounds of cargo.
Not every semi has cruise control. Older trucks, specialty vehicles, or those used primarily for local delivery may not be equipped with it. Drivers should check their owner's manual or ask their dispatcher whether their assigned truck has the feature before relying on it for a long haul.
Key Takeaways
- Modern semis typically have cruise control, but older trucks and those used for local routes may not have it installed.
- Truck cruise control is designed for highway use and works best on flat or gently rolling terrain where the engine can maintain steady power.
- Drivers must disengage cruise control when descending long grades, in heavy traffic, or on wet roads to avoid brake overheating or loss of control.
- Cruise control in a semi reduces driver fatigue on long stretches but does not replace the need for active steering and attention to road conditions.
How truck cruise control differs from passenger car cruise control
A semi's cruise control must manage much larger weight and momentum than a car's system. When a truck is loaded, the engine has to work harder to maintain speed, and the braking system faces far greater stress if the driver needs to slow down quickly. For this reason, truck cruise control systems are more conservative—they may not hold speed as precisely as a car's system, and they often have built-in delays to prevent the transmission from hunting between gears.
Truck cruise control also interacts with the engine brake, a feature that uses the engine to slow the truck without wearing out the service brakes. When a driver sets cruise control on a semi, the system coordinates with the engine brake to maintain speed on downhill sections without relying solely on the friction brakes. This is critical because overheated brakes can fail, and brake failure on a loaded semi is a serious safety hazard.
Another key difference is that truck cruise control has speed limits built into the system. Many trucking companies program the cruise control to cap out at 65 or 68 miles per hour, regardless of what the driver sets, to reduce fuel consumption and comply with company safety policies. Some newer trucks also have adaptive cruise control, which can slow the truck automatically if a vehicle ahead is detected, though this is less common in semis than in passenger vehicles.
When truck drivers should not use cruise control
Cruise control is unsafe on long downhill grades, even with the engine brake engaged. On a steep descent, gravity can overcome the engine brake's holding power, and the truck will accelerate. If cruise control is active, it may not respond fast enough, or the driver may not notice the speed increase until it is too late. Professional drivers are trained to disengage cruise control before any significant downgrade and to use a lower gear and the engine brake instead.
Heavy traffic, wet roads, and snow or ice are also situations where cruise control should be off. In traffic, the truck needs to adjust speed constantly to match the flow of other vehicles, and cruise control can delay the driver's response if a sudden stop is needed. On slippery surfaces, maintaining a constant speed can cause the wheels to lock up or the truck to skid, so the driver needs full control of the throttle and brakes.
Fatigue is another factor. While cruise control reduces the physical effort of maintaining speed, it can also lull a driver into a false sense of security. A driver using cruise control must stay alert and ready to take over when ready if conditions change. If a driver feels drowsy, the solution is to pull over and rest, not to rely more heavily on cruise control.
How to use cruise control safely in a semi
Before setting cruise control, the driver should may support the road is clear, straight, and relatively flat. The speed should be set below the truck's programmed limit and below the legal speed limit for trucks in that state or province. Most states allow trucks to travel at 65 miles per hour on interstate highways, though some allow 70. The driver should set cruise control to a speed that feels safe and sustainable for the distance ahead.
Once cruise control is engaged, the driver must keep both hands ready to steer and must monitor the road constantly. The cruise control system does not steer the truck or watch for hazards—it only maintains speed. If the driver needs to slow down, they should tap the brake pedal, which will disengage cruise control when ready. Some drivers prefer to use the resume button to return to the previous speed rather than resetting it manually.
On long hauls, drivers should disengage cruise control every 30 to 60 minutes and actively control the throttle for a while. This keeps the driver engaged and reduces the risk of falling asleep. It also gives the driver a chance to feel how the truck is handling and to notice any changes in road conditions or vehicle performance that might not be obvious when the cruise control is doing the work.
Cruise control and fuel economy in semis
One of the main reasons trucking companies install and encourage the use of cruise control is fuel economy. A truck that maintains a steady speed uses less fuel than one that accelerates and decelerates constantly. On a long highway stretch, cruise control can reduce fuel consumption by 5 to 10 percent compared to manual throttle control, which translates to significant savings over thousands of miles.
However, the fuel savings depend on the terrain and the driver's habits. On hilly terrain, cruise control may actually use more fuel because the system will downshift and explore more throttle to maintain speed on an uphill section, whereas an experienced driver might ease off the throttle and let the truck slow slightly, then accelerate again on the downhill. This is why some drivers prefer to manage speed manually on variable terrain.
Trucking companies often monitor cruise control use through the truck's onboard computer system. Dispatchers and fleet managers can see whether a driver is using cruise control, how often they are disengaging it, and what speeds they are maintaining. This data helps companies track fuel economy and driver behavior, and it can affect driver pay and safety ratings.
What to do if your semi does not have cruise control
If a truck is not equipped with cruise control, the driver will need to manage speed manually using the throttle. This is more tiring on long drives but is manageable with proper rest breaks. Drivers should take a break every two hours or every 100 miles to stretch, walk around, and rest their eyes and hands.
Some older trucks can have cruise control retrofitted, though the cost and complexity vary depending on the truck's age and the type of transmission. A driver should ask their company whether retrofitting is an option if they are assigned to a truck without cruise control regularly. For short-haul or local delivery work, the lack of cruise control is usually not a major issue because the driving is more varied and the distances are shorter.
Frequently Asked Questions
Can a truck driver use cruise control on the highway in bad weather?
No. Cruise control should be off in rain, snow, ice, or fog. In bad weather, the driver needs to adjust speed constantly and have when ready control of the throttle and brakes. Cruise control can delay response time and increase the risk of skidding or losing control.
Does cruise control work on hills and mountains?
Cruise control works on gentle hills but should be disengaged on steep grades. On a long downhill, gravity can overcome the engine brake and cruise control system, causing the truck to accelerate. Drivers must use a lower gear and the engine brake manually on significant descents.
What happens if a truck's cruise control fails while driving?
If cruise control fails, the driver will straightforward need to manage speed manually using the throttle. The failure of cruise control does not affect the truck's ability to accelerate, brake, or steer. The driver should notify their dispatcher and have the system checked at the next maintenance stop.
Is cruise control required on semis?
No, cruise control is not required by law. However, most modern semis have it as standard equipment because it improves fuel economy and reduces driver fatigue on long highway stretches. Older trucks and specialty vehicles may not have it.
Can a truck driver sleep while cruise control is on?
No. A driver must remain alert and awake at all times, regardless of whether cruise control is engaged. Cruise control maintains speed only—it does not steer, watch for hazards, or prevent accidents. Drowsy driving is illegal and dangerous, and the solution is to pull over and rest.