Many crashes usually start with a driver inadvertently leaving the lane. These lane departures broadly fall into two categories. One is where kinematic control is lost, e.g. due to icy roads. The other, and the focus here, is when the vehicle in principle remains controllable, but where the driver for some reason temporarily does not exercise that control. Developing safety systems which detect and act on inadvertent lane departures due to e.g. drowsiness and/or distraction, has a large safety potential.

However, in addition to precise threat detection, successful implementation of such systems also requires an understanding of what motivates and controls the driver’s response to system feedback. While threat detection has advanced considerably in recent years, there has yet to emerged a common view on how to understand and improve driver compliance with system feedback in imminent lane departure situations.

The objective of the paper is to formulate a theoretical framework for understanding how safety system feedback is received by the driver in different driving situations. The purpose is to enhance the understanding of what is required to achieve high levels of driver compliance in situations where systems indicate risk, for example of inadvertent lane departures.

The framework is based on the dimensions of perceived threat relevance and opportunities for action. Essentially, when system feedback is received (e.g. a lane departure warning), the driver balances the perceived potential gravity of the situation against the effort required to abide by the system’s feedback. This aligns with a general human factors trend toward describing human behavior as a balancing act between goal desirability and energy expenditure.

Application of the framework shows that if the driver associates an imminent lane departure with a low level of threat, correctional effort in response to system feedback will be minimal. To increase lane keeping precision under those circumstances, the vehicle must offer an opportunity for action that requires minimal driver effort to realize. Here, strategies like offering to turn on lane keeping aid as soon as lane keeping starts to degrade might be a way forward. If the driver on the other hand associates a lane departure with a high level of threat, any warning that manages to bring the driver’s attention back on the forward roadway will be sufficient. The exception is if the driver is incapable of comprehending or acting the warning, in which case radical actions such as autonomously driving the vehicle to the next rest place might be necessary.

To increase road safety, a deeper understanding of driver compliance is just as important as good threat detection. The issue of how to scientifically approach driver compliance needs to be a top priority in driver behavior analysis. The framework illustrates both the need for, and a viable approach to, a systematic view of how safety system feedback influences driver behavior in lane departure situations. While a step forward, much work remains before the principles governing driver compliance in potentially threatening situations are fully understood.