Driver behavior detection: how to spot abnormal driving behavior

Driver monitoring is no longer just for experts: it now concerns both road safety and risk management for insurers. In a context where dangerous driving is still responsible for a significant proportion of accidents, learning driver behavior detection has become essential. For insurance professionals, this means refining risk assessment. For individual drivers, it's about recognizing warning signs, both in themselves and in others, to prevent accidents.

This article offers a dual perspective: an analytical approach for automotive insurance experts, and an accessible explanation for the general public. The objective: to better understand abnormal driving behaviors, the technologies that help detect them, and the right reflexes to adopt to enhance everyone's safety.

1. Why driver monitoring is a major road safety issue

In France, several thousand people still lose their lives on the roads each year, despite progress in road safety. A significant proportion of these accidents are directly linked to abnormal behavior or dangerous driving.

Data shows, in particular:

• fatigue and drowsiness involved in a significant proportion of fatal accidents, especially on motorways;
• inattention (often linked to smartphones) causing a growing number of bodily injury accidents;
• alcohol involved in approximately a quarter of road fatalities;
• drugs present in nearly one in five fatal accidents.

For insurers, these figures reinforce the interest in driver monitoring tools and scoring to better price risks. For drivers, they serve as a reminder that certain signs (fatigue, distractions, substance consumption) are never insignificant behind the wheel.

2. Physical signs of abnormal driver behavior

Driver behavior detection begins with simple indicators, visible to the driver themselves, passengers, or other road users. These physical signs are often the first to appear.

2.1. Signs of fatigue and drowsiness at the wheel

Fatigue is one of the main causes of serious accidents. It manifests as:

• repeated yawning, heavy eyelids, difficulty keeping eyes open;
• very slow blinking, blurred vision or difficulty focusing;
• microsleeps lasting a few seconds, sometimes without the driver being aware of them;
• feeling of having "missed" a section of road or a motorway exit.

For individual drivers: at the first signs of drowsiness, safety is already compromised. It is recommended to stop for a real break, or even a short sleep, rather than trying to "hold on a little longer."

For insurers: taking fatigue into account in underwriting questionnaires (long professional journeys, night work, staggered hours) and the use of on-board drowsiness sensors (DDAW – Driver Drowsiness and Attention Warning systems) can refine risk assessment.

2.2. Driver under the influence of alcohol or drugs

An abnormal driver behavior can also result from alcohol or drug consumption. Typical signs are:

• slowed or slurred speech;
• hesitant gait when getting out of the vehicle;
• excessive emotional reactions (aggression, euphoria, disinhibition);
• smell of alcohol, red eyes, dilated or very constricted pupils.

For individual drivers: if you doubt your ability to drive (or that of a loved one), the only safe decision is not to get behind the wheel. Taxis, VTCs, carpooling, or spending the night on-site are always preferable to dangerous driving.

For insurers: these elements justify targeted prevention programs, or even offers conditioned by devices such as alcohol interlocks for certain profiles.

3. Indicators of dangerous driving observable on the road

Driver monitoring is not solely based on the driver's physical state, but also on their observable behavior behind the wheel. Certain driving patterns are real warning signs.

3.1. Erratic behavior: abnormal trajectories and speeds

We speak of dangerous driving or erratic driving when the vehicle exhibits inconsistent behaviors, for example:

• frequent and unpredictable lane changes without signaling;
• difficulty maintaining trajectory (weaving, repeated crossing of solid white lines);
• abrupt alternation between strong accelerations and sudden braking;
• speed much lower or much higher than the traffic flow without apparent reason.

For individual drivers: if you observe this type of behavior in another motorist, keep your distance, do not try to "reason" with them by honking, and possibly notify the authorities (112) by providing as much information as possible.

For insurers: telematics boxes can objectively measure these behaviors (speed variation, sudden braking, corners taken too quickly). This data enriches driving scoring models and makes it possible to distinguish a punctual risk from a systematically accident-prone profile.

3.2. Distraction and inattention: the role of the smartphone

Inattention has become a central issue for road safety. Using a phone while driving significantly increases the risk of accidents, especially when the driver reads or writes a message.

Typical signs of distraction are:

• gaze often directed downwards (phone) or towards the central screen;
• lack of reaction to green lights or traffic slowdowns;
• slight and regular drift to the side of the lane;
• forgotten turn signal, exceeding speed limits without realizing it.

For individual drivers: the best accident prevention is to physically place the phone out of reach while driving, or to use a "do not disturb" mode. Hands-free systems reduce but do not eliminate the risk.

For insurers: driver behavior detection related to distraction can involve on-board sensors (in-cabin cameras, head and eye movement tracking) or analysis of telematics data (micro-trajectory breaks, delayed reactions).

Equip your vehicles with Easy Finder 4G to better prevent risky behaviors

4. Modern driver monitoring and driver behavior detection technologies

Manufacturers and equipment suppliers have invested heavily in Advanced Driver-Assistance Systems (ADAS) and Driver Monitoring Systems (DMS), which are increasingly present on new models in the European Union.

4.1. ADAS and correction of dangerous driving behaviors

ADAS systems act as an additional layer of road safety:

• lane departure warning and lane keeping;
• adaptive cruise control that maintains a safe distance;
• automatic emergency braking in case of collision risk;
• blind spot detection to avoid dangerous lane changes.

These devices can sometimes compensate for occasional abnormal driver behavior (inattention, incorrect distance estimation), but they obviously do not replace responsible driving.

4.2. On-board cameras and fatigue and distraction detection systems

New-generation driver monitoring systems use cameras facing the driver's face to detect:

• slow blinks, repeated yawning, fixed gaze indicating drowsiness;
• gaze diverted from the road towards a screen or phone (distraction);
• abnormal head position, a sign of imminent falling asleep.

In case of suspected dangerous driving (fatigue or distraction), the system emits an audible, visual, or even vibrating alert to encourage the driver to regain control or stop.

For insurers: this anonymized and aggregated data can feed more refined risk analysis models. In B2B, some fleet contracts already include objectives for reducing risky behaviors through these tools.

4.3. Telematics and driving scoring for insurers

Telematics boxes or embedded mobile applications allow real driving to be analyzed over time:

• average speed and speed excesses;
• sudden braking and strong accelerations;
• driving hours (night, peak hours);
• repeated journeys on accident-prone routes.

This data can feed into a driving score, useful for personalizing premiums, offering discounts to good drivers, or triggering targeted prevention actions for at-risk profiles.

For the general public, some connected insurance contracts offer discounts in exchange for smoother and more predictable driving, which directly links driver monitoring to positive incentives.

5. Regulatory framework and legal obligations

European regulation on general vehicle safety is progressively making several driver monitoring technologies and ADAS systems mandatory on new vehicles between 2022 and 2029.

In parallel, the French Highway Code already imposes clear rules regarding:

• maximum blood alcohol level;
• prohibition of driving under the influence of narcotics;
• prohibition of using a handheld phone;
• obligation to remain constantly in a state and position to conveniently execute all maneuvers necessary for driving.

For insurers, respecting this legal framework is indispens