Stay in your lane
Various systems fall under the broad description of lane-keeping assist, because they all work to keep your vehicle from straying out of its lane. Many cars combine these functions into an integrated system, but earlier examples (and some less-expensive current ones) only apply one or two of these actions.
Lane-keeping assist is based on front-mounted cameras, which scan the road markings to determine your car’s position in its lane. There are obvious limits to this approach, however – most notably, it struggles to scan lane markings if those are faded, and merging (or splitting) lanes may confuse the control unit.
This system is temporarily de-activated by using the indicators, which signals to the car that it’s about to cross lane markings, or can be switched-off completely by the driver. This ability to turn the lane-keeping assistant all the way off is quite handy when travelling down a narrow and winding road, or when dodging potholes – ignoring the beeping and overriding any car-initiated corrections can become tiresome very quickly, so it’s sometimes helpful to just disable it altogether.
Related: The best cars for highway driving.
Lane departure warning (passive)
This is the lowest level of lane-keeping assistance, because it merely warns the driver that the car is drifting from its desired trajectory. This warning may take different forms, either separately or in some combination.
The driver will be alerted by a vibration in the steering wheel, and/or a beep from the dashboard, and/or an animated icon or warning light in the instrument cluster will let you know when your car is about to cross the lane markers. However, this system will only warn the driver, without taking any other corrective action.
Lane-keeping assistant (active)
Integrating lane departure warning combined with a steering (or braking) interface leads to the full-house, active lane-keeping assistant. The basic inputs are unchanged, but rather than only warn the driver if the car is straying, this system also applies steering corrections to steer the vehicle back into its lane.
In cars without electric power assistance (or in earlier and cheaper implementations), the car’s trajectory can be adjusted by selectively applying the brakes on individual wheels, to literally drag the car back into line. This approach has not proven to be very popular, however, and has fallen by the wayside in recent years.
Lane change assistant
The latest evolution of the lane-keeping assistance system incorporates lane-changing assistance, where the front camera is augmented by side-mounted proximity sensors (also used in blind-spot monitoring), to determine if there is a clear path into the next lane.
When the driver wants to initiate a lane change with the cruise control activated, they would simply tap the car’s indicator stalk in the desired direction, and, if the way is clear, the car will smoothly slot into place in the next lane. This feature is generally only found on cars which incorporate adaptive cruise control, however, because safety concerns may dictate that the system needs to know the relative speed of the surrounding traffic as well.
