What does a speed limiter do?

A speed limiter electronically caps a vehicle’s maximum speed by reducing engine or motor power once a preset threshold is reached, helping drivers stay within limits, cut crash risk, and improve efficiency; it typically does not apply the brakes and can be fixed (factory-set) or adjustable by the driver or fleet. Beyond that simple function, modern limiters range from basic maximum-speed governors to Intelligent Speed Assistance systems that reference maps and cameras to match posted limits, and their use is increasingly mandated in commercial fleets and, in the European Union, in new passenger vehicles.

How a speed limiter works

At its core, a speed limiter compares real-time vehicle speed to a set value and intervenes when the target is exceeded. In internal-combustion vehicles, the engine control unit limits torque—usually by trimming fuel, air, or spark—so the car can no longer accelerate beyond the set speed. In electric vehicles, the inverter and motor controller cap torque output, sometimes blending gentle regenerative resistance at high speeds. Most systems do not actively use the service brakes; instead, they prevent additional acceleration and let the vehicle coast down if the road gradient or conditions allow.

Types of speed limiters you’re likely to encounter

Speed limiters come in several forms, from simple factory governors to map-aware systems that read speed-limit signs. The following list outlines the most common categories and how they differ.

• Factory maximum-speed governor: A fixed cap set by the manufacturer (for example, many performance cars have historically been limited to about 250 km/h or 155 mph) to balance safety, tire ratings, and driveline durability.
• Driver-set limiter (often labeled “LIM”): Lets the driver choose a ceiling (say, 100 km/h). The car accelerates normally up to that value and then limits further power. Many systems allow a full-throttle “kickdown” override for emergencies.
• Intelligent Speed Assistance (ISA): Uses camera-based sign recognition and/or GPS map data to identify the posted limit and then warns the driver and/or gently limits power to help maintain compliance. In the European Union, ISA is mandated on new vehicles sold from 2024 onward; drivers can typically switch it off for a trip, but it defaults on each restart.
• Fleet/telematics limiter: Remotely configured caps for commercial vehicles, often paired with driver coaching, data logging, and geofencing to enforce company policy and regulatory compliance.
• Geofenced micromobility limiters: E-scooters and e-bikes in shared fleets that automatically reduce speed in designated zones (for example, slow-streets or promenades).
• Valet/teen modes: Owner-selectable profiles that restrict top speed and sometimes acceleration for inexperienced drivers or parking valets.
• Rev limiter vs. speed limiter: A rev limiter protects the engine from over-speeding in a given gear; a speed limiter caps the vehicle’s road speed regardless of gear. Some vehicles use both.
• “Soft” vs. “hard” limiters: Soft limiters progressively reduce power as the set speed is approached; hard limiters produce a firm cutoff the moment the threshold is crossed.

Across these variations, the shared goal is to prevent excessive speed without compromising control, using torque management rather than abrupt braking to keep the experience predictable and safe.

What it does—and does not do—on the road

Here’s what drivers can expect a speed limiter to accomplish in everyday use.

• Caps maximum speed by reducing available torque once the set limit is reached.
• Supports compliance with posted limits, particularly when paired with ISA sign recognition and map data.
• Reduces crash severity by curbing top speeds and discouraging speeding-related risk-taking.
• Improves fuel economy and reduces emissions in combustion vehicles; helps EVs avoid inefficient high-speed operation and thermal stress.
• Cuts wear on tires and driveline components that escalates at higher speeds.
• In fleet applications, can log and report speed compliance for safety programs and insurance incentives.

These functions make speed limiters a practical safety and cost-control tool, especially on long highway drives and in commercial operations where consistency matters.

There are also important limits to the technology that drivers should understand.

• It is not cruise control; it prevents speeding but does not hold a set speed, especially on hills.
• Most systems do not apply the service brakes; they mainly prevent additional acceleration and may allow coasting above the limit on steep descents.
• It is not a collision-avoidance system; it doesn’t replace attentive driving, braking, or lane-keeping.
• It can be misled by incorrect map data or misread speed-limit signs; drivers remain responsible for compliance.
• Tampering or disabling the limiter may be illegal and can void warranties or insurance coverage.

Understanding these boundaries helps drivers use the feature effectively without over-relying on it for tasks it wasn’t designed to handle.

Legal landscape and real-world adoption

Regulation and adoption vary by region and vehicle class. In the European Union, Intelligent Speed Assistance has been required on new vehicle types since 2022 and on all new vehicles sold from 2024, making ISA a baseline feature in the market. Many jurisdictions mandate limiters for heavy commercial vehicles and public-transport fleets to standardize speeds and improve road safety. In North America, speed limiters for heavy trucks are widely used by fleets, and federal regulators have explored rulemaking to require electronic limiters on certain commercial vehicles, though proposals and thresholds remain under review. Shared micromobility providers and private fleets also use geofenced limiters to comply with local rules and reduce risk in sensitive zones.

Benefits and trade-offs

Speed limiters deliver measurable safety and cost gains, though they can also introduce practical trade-offs that drivers and operators should consider.

• Safety: Lower top speeds reduce kinetic energy in crashes and encourage more uniform traffic flow.
• Cost: Lower speeds reduce fuel or energy use, tire wear, and maintenance costs.
• Environment: Cutting high-speed operation curbs emissions in combustion vehicles and extends EV range.
• Compliance: ISA and fleet limiters help align driving behavior with speed limits and company policy.

Balanced against these benefits are operational considerations such as driver acceptance, the need for accurate map and sign data, and ensuring that limiters don’t impede safe overtaking or merging when a temporary burst of speed is necessary.

Practical tips for drivers

If your vehicle has a speed limiter or ISA, a few habits can make it more effective and less intrusive.

• Learn the controls: Many cars have a LIM button separate from cruise control; use the steering-wheel toggles to set and adjust the ceiling.
• Understand overrides: Some systems allow a full-throttle kickdown to briefly exceed the limit for safety; know how yours behaves.
• Keep data fresh: Map updates and clean camera lenses improve ISA accuracy; schedule software updates when available.
• Watch the dash: Speed-limit icons and color changes warn of mismatches between vehicle speed and the posted limit.
• Check tires: Ensure tires meet the speed rating appropriate for your vehicle’s factory limiter and intended speeds.
• Use judgment: Even with a limiter, conditions (weather, traffic, road work) may require driving well below the cap.

Applied thoughtfully, these practices help the limiter support rather than disrupt your driving, especially in varying road and traffic conditions.

Frequently asked specifics

Can a speed limiter be removed? In many regions, defeating a limiter on a road-going vehicle can be illegal and may void insurance or warranties. For fleet vehicles, it may also violate company policy. Always check local law and manufacturer guidance.

Does ISA brake the car? EU-compliant ISA primarily warns and reduces engine or motor power; it generally does not apply the service brakes unless the vehicle also has integrated adaptive cruise or automatic braking features.

Why do EVs often have modest top speeds? High speeds rapidly increase aerodynamic drag and power demand, hurting range and thermal management. Manufacturers often cap EV top speeds to balance performance, efficiency, and component longevity.

Summary

A speed limiter prevents a vehicle from accelerating past a set speed by limiting available power, not by braking. Found in forms ranging from simple driver-set caps to Intelligent Speed Assistance that reads signs and maps, limiters enhance safety, compliance, and efficiency while leaving drivers in control. Their growing adoption—especially in EU passenger cars and commercial fleets—reflects a clear road-safety benefit, provided drivers understand how they work and where their limits lie.

What happens when you hit the speed limiter?

When the pre-determined speed is met, the computer restricts the flow of fuel and air to the engine. Therefore, as a driver, you will not be able to exceed the pre-determined top speed. However, all speed limiters can be overridden. If there is a need to speed up quickly, pushing down hard on the accelerator will work.

What is the purpose of a speed limiter?

To prevent you from driving any faster, speed limiters use GPS data and speed sign recognition software to make a note of the maximum speed limit of where you’re driving. This information is then sent to the engine’s computer.

Are speed limiters good?

The speed limiter is a good safety tool and it helps drive in a more economical and eco friendly way (it limits the fuel air mix into the engine, thus saving money and burning less fuel).

Is it illegal to take off a speed limiter?

Yes, taking off a speed limiter is often illegal in many jurisdictions and can lead to fines, penalties, and issues with your insurance. While it’s possible to remove a speed limiter through vehicle computer reprogramming or aftermarket devices, doing so is highly inadvisable for street use. Speed limiters are in place to ensure safety by preventing vehicles from exceeding the safe speed rating of their tires and components, and bypassing them poses significant risks to the driver, vehicle, and others on the road. 
Why Speed Limiters Are in Place

• Tire Safety: Speed limiters are primarily installed by manufacturers to prevent drivers from exceeding the maximum speed rating of the factory-equipped tires, which could lead to tire blowouts and accidents. 
• Vehicle Performance Limits: They also account for other factors, such as the vehicle’s braking and stability capabilities, ensuring the vehicle operates within its designed safety parameters. 
• Manufacturer Liability: Speed limiters protect manufacturers from liability issues by ensuring vehicles aren’t driven beyond their safe operational limits. 

Risks of Removal

• Legal Consequences: You could face fines, penalties, or suspension of your driving privileges for violating local laws and regulations regarding speed limiting devices. 
• Insurance Issues: Removing the speed limiter can also compromise your insurance coverage in the event of an accident. 
• Vehicle Damage: Exceeding the vehicle’s designed speed limits can put excessive strain on mechanical components, potentially leading to damage or failure. 
• Safety Hazards: Increased vehicle instability and reduced control at higher speeds can create dangerous driving conditions. 

Legality and Responsibility

• Jurisdictional Laws: Opens in new tabWhether it’s strictly illegal depends on the specific laws in your region, so it’s crucial to check the regulations in your area before considering any modification. 
• For “Off-Highway Use Only”: Opens in new tabModifications to remove speed limiters are often intended for off-road or track use, with a disclaimer stating they are for “off-highway use only”. 
• Tire and Skill Assessment: Opens in new tabIf you do remove a speed limiter, it is imperative to ensure your tires and driving skills are capable of handling the higher speeds safely.