Why carmakers put speed limiters on cars

They fit speed limiters primarily to improve safety and comply with law, while also protecting components and reducing emissions and noise. In recent years, rules in places like the European Union and Great Britain have made “Intelligent Speed Assistance” (ISA) standard on new cars, and long-standing regulations cap speeds on heavy trucks and buses in many countries. Beyond regulation, engineering limits (tires, brakes, motors), insurance and fleet policies, and environmental goals all drive the use of speed limiters.

What a speed limiter is

A speed limiter is any system that prevents or discourages a vehicle from exceeding a chosen or mandated speed. Modern systems are electronic and can be fixed to a single maximum or dynamic, using maps and cameras to track the posted limit.

Here are the common types you’re likely to encounter.

• Top-speed governors: A hard cap set by the carmaker (for example, 180 km/h or 112 mph) to stay within tire, brake, and drivetrain limits.
• Intelligent Speed Assistance (ISA): Uses camera-based sign recognition and GPS/map data to warn the driver or gently resist acceleration past the posted limit; required on new cars in the EU since July 2024 (all newly registered vehicles) and adopted in Great Britain on new cars in 2024, with driver override allowed.
• Fleet and geofenced limiters: Company, municipal, or rental fleets set lower, non-overridable caps (e.g., 65–70 mph/105–113 km/h) or enforce low speeds in zones like depots, school streets, or city centers.
• Mechanical/electronic throttle limiters: Older mechanical governors and modern ECU-based controls that trim fuel, throttle, or motor torque once a threshold is reached.

Together, these systems range from advisory aids that the driver can push through, to firm caps that the vehicle will not exceed under power.

Why they are installed

Manufacturers, regulators, and fleet owners rely on speed limiters for a mixture of safety, legal, engineering, and economic reasons.

Below are the main drivers behind speed limiter adoption.

• Safety: Lower speeds reduce crash likelihood and severity, shorten stopping distances, and improve survivability for people inside and outside the vehicle.
• Regulatory compliance:
  – EU General Safety Regulation (2019/2144) mandates ISA on new vehicle types since July 2022 and on all newly registered vehicles since July 2024; system must default on at start-up and be easily overridable.
  – Heavy goods vehicles and coaches in the EU/UK are capped (commonly ~90 km/h for trucks and ~100 km/h for many coaches).
  – Other regions cap commercial vehicles similarly (e.g., Australia, Japan, India).
• Engineering limits: Tires have speed ratings; brakes, bearings, driveshafts, and EV motors have thermal and rpm limits. A limiter keeps the car within designed tolerances.
• Environmental and cost benefits: Lower highway speeds cut fuel use and CO₂, curb NOx and particulate emissions, and extend EV range; fleets save on fuel and maintenance.
• Noise and community impact: Slower speeds reduce road and tire noise, important for urban areas with strict noise standards.
• Insurance and liability: Fleets and families use limiters to manage risk, often earning lower premiums and fewer violations.
• Market conventions: Some brands limit road cars by policy (e.g., the long-standing 250 km/h “gentleman’s agreement” among German marques, or specific caps like 180 km/h on certain models).

In short, capping speed is a practical, measurable way to cut risk and cost while ensuring vehicles operate within their certified design envelope.

Regulations and policies at a glance

Rules differ by country and vehicle class. Here’s how key markets approach speed limiters today.

• European Union: ISA required for new types since July 2022 and for all new registrations since July 2024; drivers can override momentarily. Heavy trucks typically limited to about 90 km/h and many coaches to about 100 km/h.
• Great Britain (UK): GB has moved to align with EU-style safety features, with ISA required on new cars introduced in 2024; like the EU, ISA can be overridden by the driver during a trip.
• United States: No federal requirement for passenger-car limiters or ISA. A nationwide heavy-truck speed limiter rule has been proposed but not finalized; many private fleets self-limit. Cities such as New York have piloted ISA on municipal fleets.
• Australia: Heavy vehicles (generally over 12 tonnes GVM) are limited to 100 km/h; additional limits may apply to buses depending on state.
• Japan: Large trucks and buses are restricted (around 90 km/h); passenger cars are not broadly mandated, though many models are electronically limited.
• India: Speed governors mandated for many transport and commercial vehicles (often around 80 km/h), with implementation and enforcement varying by state.

The overall trend is toward broader adoption of intelligent, overridable systems for passenger cars and firm caps for commercial vehicles, with details tuned to local road policy.

How speed limiters work in practice

Sensing and data

ISA blends camera-based traffic sign recognition with GPS and map data to estimate the current limit, then alerts the driver or gently resists additional throttle above that speed. Accuracy depends on clean camera views and up-to-date maps; construction zones and temporary signs can challenge any system, which is why driver responsibility remains paramount.

Driver override and behavior

EU/GB ISA rules require that drivers can temporarily override by pressing the accelerator through a tactile “hump” or by switching the system off for the current trip. Heavy trucks and some fleet vehicles use non-overridable caps. Studies show advisory or lightly resisting systems reduce average speeds without causing heavy-handed interventions.

Calibration, tires, and components

Top-speed governors are set against the vehicle’s tire speed rating and component limits. Switching to lower-rated winter tires can prompt a lower software cap. In EVs, caps help manage motor rpm and battery/thermal constraints at very high road speeds.

Common concerns and misconceptions

Speed limiters raise practical and philosophical questions. Here are frequent concerns, with context on how systems address them.

• Overtaking safety: ISA in passenger cars is designed to be overridable for short bursts when needed; hard caps are typically reserved for heavy vehicles and specific fleets.
• Sign or map errors: ISA is advisory/resistive and can be switched off during a trip; the driver remains responsible for choosing a safe, legal speed.
• Privacy: ISA itself doesn’t require sending location data; however, separate fleet telematics may track speed and routes for business and safety purposes.
• Enthusiast use: Some cars offer higher limits or “track modes” off public roads; on-road limits reflect safety, legal, and component constraints.

While not flawless, modern systems aim to balance driver control with tangible safety and efficiency gains, and most are engineered to be minimally intrusive during normal driving.

What it means if your car has one

If your vehicle includes a limiter, a few habits will help you use it effectively and avoid surprises.

• Learn the settings: Know how to adjust ISA modes, accept or decline speed prompts, and override when appropriate; many systems default to “on” each start.
• Mind your tires: Never exceed your tires’ speed rating, and be aware that winter tires or lower-rated replacements can reduce the car’s permissible top speed.
• Keep sensors current: Update maps and keep cameras/radars clean for better speed-sign recognition.
• For fleets: Set clear speed policies, review telematics ethically and legally, and train drivers on safe use and exceptions.

Used correctly, limiters become a background safety net that reduces risk and running costs without getting in the way of routine driving.

Summary

Speed limiters exist to cut crash risk, satisfy regulations, and protect vehicles, with additional benefits for emissions, noise, and operating costs. The EU and Great Britain now require Intelligent Speed Assistance on new cars (overridable by the driver), and many regions cap heavy vehicle speeds. Carmakers also apply top-speed governors for engineering reasons. Although concerns remain about accuracy and autonomy, modern systems are designed to be transparent and minimally intrusive, delivering measurable safety and efficiency gains on real roads.

Why do cars have speed limiters?

Safety Improvements: The implementation of speed limiters could lead to a decrease in high-speed collisions, which are often more severe and deadly than accidents at lower speeds. This could improve overall road safety for drivers, passengers, and pedestrians alike.

Can speed limiters be turned off?

Exactly how you turn the limiter on and off varies from car to car. It may be a button on the steering wheel or an option in the same settings menu as other driver assistance features such as lane keeping assist. There may also be the option of turning the limiter permanently.

Are speed limiters mandatory in the US?

The Federal Motor Carrier Safety Administration (FMCSA) has officially withdrawn its proposed rule mandating speed limiters on commercial motor vehicles, effective July 24, 2025, as published in the Federal Register.

What is the point of a speed limiter?

What’s the point of a speed limiter? It’s a safety device, and makes a long journey easier to complete. It relieves you from the need to keep checking your speed, by restricting your ability to exceed the speed limit (or any other speed that you might set).