Lane Drift

New research data from the Insurance Institute for Highway Safety (IIHS) indicates that lane departure warning systems lower rates of single-vehicle, sideswipe, and head-on crashes of all severities by 11 percent and lower the rate of injury crashes of the same type by 21 percent. While encouraging, several limitations currently exist preventing this life-saving technology from reaching its full potential.

The latest data in this ongoing study, led by IIHS vice president for research Jennifer Cicchino, is based on 2015 police crash reports, which includes information on the circumstances of the crash, allowing researchers to examine the types of crashes that lane departure warning systems are designed to prevent.

“This is the first evidence that lane departure warning is working to prevent crashes of passenger vehicles on U.S. roads,” said Cicchino. “Given the large number of fatal crashes that involve unintentional lane departures, technology aimed at preventing them has the potential to save a lot of lives.”

A 2015 study of lane departure warning on trucks in U.S. fleets found lane departure warning systems cut the rate of relevant crashes nearly in half, a reduction greater than the new data. A similar study of Volvo cars in Sweden found a reduction of relevant injury crashes of 53 percent.

AAA believes that lane departure warning could totally eliminate almost 50 percent of all head-on collisions. Why hasn’t current test data shown those results? Greg Brannon, the Automobile Association of America’s director of automotive engineering, called IIHS’ studies “encouraging,” but said that drivers need to understand the limitations as well as the capabilities of the safety technology in their vehicle.

Limitations within Lane Departure Warning Technology

There are two types of lane departure warning systems, activated by unintended lane departure:

  • Lane departure warning systems (LDW) which give the driver visual, audible, and/or vibrating warnings when the vehicle is leaving its lane
  • Lane keeping systems (LKS) which automatically take steps to ensure the vehicle stays in its lane

Lane warning and lane keeping systems are based on:

  • Video sensors mounted behind the windshield, typically beside the rear mirror
  • Laser sensors mounted on the front of the vehicle
  • Infrared sensors mounted either behind the windshield or under the vehicle

Because they rely on visible lane markings, lane departure warning systems typically cannot decipher faded, missing, or incorrect lane markings or markings covered in snow or obscured by rain or excessive glare from the sun.

Few Vehicles on the Road with Lane Departure Warning Systems

In 2000, the United States company Iteris developed the first lane departure warning system in Europe for Mercedes Actros commercial trucks.

In 2002, the Iteris system became available on Freightliner Truck’s North American vehicles. With this system, the driver is warned of unintentional lane departure by an audible rumble strip sound on the side of the vehicle drifting out of the lane, but the warning is not generated if the driver gives an active turn signal before crossing the lane.

Honda was the first U.S. passenger vehicle automaker to introduce this feature, with its Lane Keep Assist System (LKAS) on the 2003 Inspire.

Nissan followed in 2004 with its Infiniti FX and in 2005 on the M vehicles, which issues a warning tone to alert the driver when the vehicle begins to drift over lane markings.

Also in 2004, Toyota added a Lane Keeping Assist feature to the Crown Majesta, which applies a small counter-steering force to aid in keeping the vehicle in its lane.

In 2006, Lexus introduced a multi-mode Lane Keeping Assist system on the LS 460. The LS 460’s LKA system issues an audiovisual warning, steers the vehicle to hold its lane, and applies counter-steering torque to ensure the driver does not over-correct the steering wheel while attempting to return the vehicle to its proper lane.

Audi began offering its Audi Lane Assist feature in 2007 on the Q7. This system will not intervene, but will vibrate the electric power-steering system when it detects an unintended lane departure. The electric power-steering system will then introduce a gentle torque that will help guide the driver back toward the center of the lane. However, a driver engaging the turn signal or accidently leaving it on will prevent the Lane Assist feature from functioning.

As of 2017, most car makers offer both lane departure warning and/or lane keeping assist as optional features on some of their models, usually in the higher price ranges, with fewer as standard.

Combining the Human Factor with Lane Departure Warning Technology

Driver assist technology will continue to improve with better, more reliable features, but the greatest challenge will be working the driver into the equation. Technology is still a poor substitute for an alert driver, and must rely on driver response to an impending emergency.

A turn signal will temporarily disable lane departure warning and lane keeping systems to allow a driver to complete a turn. If it is left on unintentionally, the system will not work when it is needed. Some drivers, irritated by lane departure warning sounds, also intentionally disable the feature.

Lane departure warning systems require an appropriate response from drivers, who may be unable to respond. IIHS research found that in 631 lane-drift crashes, 34 percent of the drivers were physically incapacitated, either asleep or unconscious due to drugs or alcohol, seizures, heart attacks, strokes, or diabetic shock. Whether or not these systems can prevent a crash depends on how the system responds if the driver doesn’t take control after the system has intervened.

“If drivers are physically unable to control the vehicle, it’s not enough to only nudge the car back into the lane. In such cases, a crash avoidance system would need to bring the vehicle to a stop on the side of the road,” said IIHS vice president for research Jessica Cicchino.

Unfortunately, drifting to the side of the road could also take the vehicle to a narrow shoulder still within the flow of traffic, or over the side of a cliff.

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