Fewer accidents due to lane keeping assist function and variants

More than ten percent fewer people involved in road accidents in 2020 than in the previous year. The main reason is believed to be reduced traffic due to the ongoing pandemic. Still, every fatality on the road is one too many. There are numerous driver assistance systems on the road these days to keep you safer, including: Lane Keeping Assist. In today's post, we'll look at how they work and go over the differences in active and passive lane departure warning systems a.

What is a lane departure warning system?

A lane departure warning system (LWD)/ lane keeping assistant system (LKAS) supports the driver of a motor vehicle in road traffic in keeping to the lane. This is a driver assistance system that is installed in the vehicle. Nowadays, lane departure warning systems are usually standard equipment on new cars.

Lane departure warning systems are designed to assist riders in the event of an unintended lane change due to

Microsleep at the wheel, – loss of concentration, and – driver inattention


EU distinguishes lane departure warning systems from emergency assist systems. According to Article 3 of EU Regulation 2018/858 and EU Regulation 2019/2144, the Lane departure warning system Defined as "a system that warns the driver when the vehicle unintentionally leaves its lane". A Emergency Lane Keeping Assist (ELK – Emergency Lane Keeping), on the other hand, is "a system that assists the driver in maintaining a safe vehicle position in relation to the lane or road boundary, at least when the vehicle is leaving or about to leave its lane and a collision may be imminent."

A few years ago, the International Society for Automotive Engineering already developed a step-by-step model of autonomous driving. This classifies the degree of automation of a vehicle. Are simple driver assistance systems, such as lane departure warning systems, classified as "assisted driving" from the first stage onwards. But there are also more complex lane departure warning systems, which are counted as level two "partially automated driving".

More information on the phased model of autonomous driving:

The step-by-step model of autonomous driving

Is a lane departure warning system mandatory?

Lane departure warning systems have been mandatory for newly registered trucks weighing 3.5 metric tons or more since 2013. The same applies to buses with more than eight seats. For passenger cars, there is no obligation for a lane departure warning system so far. However, this will soon change. In 2019, the EU has decided that certain driver assistance systems must be mandatory in new vehicle types as well as newly registered vehicles.

The amendment is set out in the EU Regulation "concerning the type-approval of motor vehicles and their trailers, and of systems, components and separate technical units intended for such vehicles, with regard to their general safety and the protection of the occupants and vulnerable road users". Among them Emergency lane keeping assistants become mandatory for passenger cars and light commercial vehicles (vehicle classes L, M, N). This applies from 6. July 2022 for all passenger cars type-approved in the EU. From 7. July 2024, all newly registered passenger cars must also be equipped with an emergency lane departure warning system. The obligation also applies to other driver assistance systems, including emergency braking systems, tire pressure gauges, a drowsiness warning system and an interface that enables alcohol-sensitive immobilizers.

You can find out more about driver assistance systems in general in the following article:

Safer on the road with driver assistance systems

Fewer accidents due to lane keeping assist function and variants

How a lane departure warning system works

In most car manufacturers, the lane departure warning system includes a small video camera, which is mounted behind the windshield. This is to record when the driver leaves the space between the lane markings. The camera captures the contrasts of the lane lines. A system is connected to the camera, which evaluates the optically recorded information and compares it with the position of the vehicle. As soon as the vehicle falls below a defined minimum distance from the lane line, the lane departure warning system intervenes. To what extent the assistant intervenes depends on the respective system. The different variants of lane departure warning systems are explained in more detail in the following section.

Variants of lane departure warning systems

There are a number of different names for lane departure warning systems, depending among other things on the different car manufacturers. However, many terms mean the same thing. An overview of the most important variants and designations:

Active Lane Keeping Assist vs. Passive lane departure warning

The biggest difference is between active and passive lane departure warning systems and is essentially based on the distinction made by the EU.

Active lane departure warning systems then correspond to emergency lane departure warning systems and passive lane departure warning systems can be assigned to the lane departure warning systems. The latter are usually acoustic, haptic or visual signals that warn the driver when he or she is leaving the lane. For this reason, many manufacturers also refer to it as a lane departure warning system Lane departure warning titled. A common warning signal in vehicles with passive lane departure warning is the vibration of the steering wheel as soon as the vehicle is no longer kept in its lane. The driver should be alerted at an early stage. Can still react accordingly. If the turn signal is set to change lanes, the warning signal is deactivated.

The Active Lane Keeping Assist again, as the name suggests, actively intervenes in the driving style. This is also often referred to as Lane Assist or Lane departure warning with steering intervention referred to as. In vehicles with electric power steering, the active lane departure warning system can countersteer when the driver leaves the lane. For some automakers, this system only takes effect above a certain speed. As a rule, the driver must have both hands on the steering wheel for the lane departure warning system to work (hands-on-detection). In other vehicles, however, the system can also intervene by means of ESP through controlled braking of the wheels. If this is not the case, many types of vehicles sound a warning signal. In trucks, the lane departure warning system operates via the hydraulic system. However, the driver can intervene at any time.

Lane Change Assistant

In addition to lane departure warning systems, there are also Lane Change Assist. These work in a similar way to lane departure warning systems. If a dangerous situation arises during the lane change, for example due to other road users, the system can warn the driver. For this purpose, two radar sensors are attached to the rear of the vehicle, covering the areas next to and diagonally behind the vehicle. If vehicles are detected in the car's blind spot, for example, a visual, acoustic or haptic signal is also emitted here. Widely used are light symbols in the vehicle's exterior mirrors that flash as soon as another road user or an obstacle is in the detected areas.

Retrofitting a lane departure warning system?

Currently only newer vehicle models have lane departure warning built in. But the assistance system can also be retrofitted to older models. However, these are mostly passive lane keepers. It is helpful if the vehicle already has traffic sign recognition. Otherwise, retrofitting is quite complex and costly. Active support is difficult to retrofit in very old vehicles, as software adjustments are also necessary. Unsuitable, on the other hand, are lane departure warning systems via smartphone or dashcam, as they generally lack the necessary sensors.

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