BASICS OF AND IDEAS BEHIND LANE DEPARTURE WARNING
DISCLAIMER: This webpage presents information in a potential area of automotive advanced safety system technology. The information presented in this webpage is in no way intended to be, either directly or indirectly, representative of completely formulated and organized aspects of the respective technology, and should not be assumed to be such unless it is expressly indicated to the contrary by the inventor via a formal notification method of his choosing. It is not intended to take the place of laws, regulations, safe driving habits or common sense. ALWAYS DRIVE SAFELY! This proviso may apply to any other works by the inventor.
Basics start with constituent words. What is meant by the phrase "LANE DEPARTURE"? What is a "LANE DEPARTURE WARNING"? To answer those questions, it might be best to first consider the two words "LANE" and "DEPARTURE" separately.
The word "LANE", very simply put and in the context of vehicular traffic, might be thought of as “a travel boundary for a vehicle operator”. Similarly, the word "DEPARTURE" might be thought of as “the change to a travel boundary”. Thus, the phrase "LANE DEPARTURE" might be looked at as “the operational change of a vehicle from within a current travel boundary to outside the current travel boundary”. Hence, a "LANE DEPARTURE WARNING" might be described as "a notification to a vehicle’s occupants that a lane transition is occurring which they should be alerted to". This alert may be visual, audible, haptic, or any combination of the three.
Tasks related to roadways, simplified. A lane departure warning system needs to be able to perform many tasks. Two of the most vital are its ability to recognize likely longitudinal lane markings from the field of view and then to formalize a relationship for the positioning of the vehicle with respect to those boundaries. However, a lane departure warning system may extract more than just likely longitudinal lane boundaries toward relative vehicle positioning. It might also potentially use demarcations to contribute to a multi-parameter model of the roadway supporting a more thorough and robust understanding of the "travelled way". With a comprehensive roadway model comes the increased possibility for path prediction as (potentially) supported by other sensing modalities and roadway geometry resources. This website contains further details on my invention as well as further explanation as to how image analysis may be performed for lane departure warning systems.
Challenges to overly simplified explanations. Due to the very complex nature of the problem domain, identifying precisely when the departure from a lane occurs and how to alert a vehicle operator to its occurrence are circumstances likely best left up to the vehicle manufacturers and/or organizations that are responsible for governing the function and performance of these systems. There are many different types of vehicles which may be equipped with lane departure warning systems. Additionally, there are many different legislative bodies around the world which handle roadway rules and regulations according to their own government guidelines. In general, assuming a vehicle is safely operating within a lane boundary on a given roadway, then there would also be a point when a portion of that vehicle would be considered as having crossed an established borderline which delineates that lane from a different lane.
Lane marker transitions, borders, projection lines and relative positioning. A longitudinal lane marker may simply be looked at as having two borders, one for the "darker to lighter" transition and another for the "lighter to darker" transition. Consider the following image which contains some potential structure for a "broken" white lane marker.
This website shows many road scene images with superimposed forward and rearward projection lines which may be used to support relative positioning relationships. Consider the following image which shows how forward and rearward projection lines may be formulated from a line segment potentially representing a border of a longitudinal lane marker.
This process may be used to formulate innermost and outermost projection lines where the innermost are typically designated by dashed red or yellow lines and the outermost are typically designated by dashed red lines. Consider first the following image which shows projection lines for a vehicle which is clearly within a lane boundary.
Consider next the following image which shows projection lines for a vehicle which is clearly not within a single lane boundary.
Related LDW complicating factors. There are many complicated issues related to lane departures including (but not limited to) intent, right of way, obstructions, human factors, environmental conditions, dynamic vehicle operating conditions and more. Consumers might be aware that two of the principal components of a lane departure warning system are the camera system and the vehicle alert system. However, there are many other complicated safety devices and mechanisms which may interface with those components and the vehicle operator including (but not limited to) the steering system, the cluster and/or head up display, the rear view mirror system, the braking and acceleration systems, the radar and/or ultrasonic systems and more. Systems may be designed to predict if a lane departure might occur, when it will likely occur, when it is imminent as well as to alert when one is occurring. I have compiled a more comprehensive list of factors affecting lane delineation. This list is accessible via the 'further explanation..' text link in the Tasks.. heading above.
Consider the potential block diagram for a general road scene image processing system.
Additional resources. Many other resources are available for further explanation of both lane departure warning technology and the roadways on which vehicles may travel.
The previous road scene images showing projections were generated using Matlab Student Version from The MathWorks.
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