NL2036643B1 - System and method for continuously monitoring intoxication of a driver of a vehicle - Google Patents

Abstract

Title: SYSTEM AND METHOD FOR CONTINUOUSLY MONITORING INTOXICATION OF A DRIVER OF A VEHICLE ABSTRACT Disclosed herein are a system and method for continuously monitoring intoxication of a driver of a vehicle. A breath sample is received from the driver and a baseline concentration of intoxicant is measured in the breath sample. The engine is allowed to be started when determining that the baseline concentration is lower than an allowable concentration threshold. While the engine is running, a measurement value is retrieved from each of the one or more ambient sensors, representative of the ambient concentration of intoxicant in the ambient air in the cabin. Each measurement value is normalized by scaling with a predetermined baseline value. Each normalized value is compared to a respective threshold value, and in response to determining that at least one of the normalized values exceeds the respective threshold value, an alert signal is generated. [FIG 1]

Description

P136173NL00

Title: SYSTEM AND METHOD FOR CONTINUOUSLY

MONITORING INTOXICATION OF A DRIVER OF A VEHICLE

The invention relates to a system and method for continuously monitoring intoxication of a driver of a vehicle, in particular while the vehicle is being driven.

Road traffic accidents claim a significant number of lives worldwide, and alcohol consumption remains a leading cause of these incidents. For example, in European countries such as the Netherlands, alcohol-impaired driving continues to be a concern, contributing to a substantial number of road fatalities. In the Netherlands alone it is estimated that alcohol consumption in traffic leads to 75-140 road deaths annually with a significant portion of these incidents attributable to serious alcohol offenders, i.e. offenders who have been apprehended with a blood alcohol content (BAC) higher than 1.3%. at least once.

According to the SWOV (the national scientific institute for road safety research), the Netherlands is home to a considerable number of serious alcohol offenders, with estimates ranging from 90,000 to 125,000 individuals. Shockingly, these offenders are responsible for two-thirds of all serious alcohol-related crashes. Law enforcement agencies arrest approximately 7,500 of them each year. Troublingly, at least 45% of these individuals exhibit persistent offending behavior, continuing to drive under the influence of alcohol even after being apprehended by the police, thereby becoming repeat offenders. The social costs associated with this group of offenders are staggering, estimated to amount to between 0.8 and 1.8 billion euros annually.

Addressing the issue of repeat alcohol offenders is of paramount importance to reduce the societal impact of alcohol-related driving offenses and enhance road safety in the Netherlands.

It 1s known to install an ignition interlock system in a vehicle, to prevent impaired drivers from operating the vehicle. These systems may require the driver to scan their driver’s license and provide a breath sample, e.g. by blowing into a breathalyzer before starting the vehicle. The ignition interlock interrupts the signal from the ignition to the starter until a valid breath sample is provided that meets maximal alcohol guidelines in a local

Jurisdiction. At that point, the vehicle can be started as normal. By measuring the alcohol content in the breath sample, the system determines the driver's sobriety level. If the alcohol content surpasses a predefined threshold, the ignition is locked, effectively preventing the vehicle from starting.

Known alcohol ignition lock systems, or alcolocks, have proven to be effective in reducing recidivism compared to driving license disqualification or a declaration of driver's license invalidity. However, the reliability of known systems can still be improved as they are sensitive to tampering efforts. An intoxicated driver may for example try to influence the system’s measurements, e.g. by hyperventilating before providing the breath sample, or get a sober passenger in his vehicle to provide the breath sample.

SUMMARY

The present disclosure addresses the limitations of prior art ignition interlock systems and methods, by providing a more accurate and reliable detection of the state of intoxication of a driver. For this purpose, aspects of the present disclosure relate to a system for continuously monitoring intoxication of a driver of a vehicle, in particular while driving the vehicle.

The system comprises a breath detection unit and an ambient detection unit. The breath detection unit is arranged for receiving a breath sample from the driver and for measuring a breath concentration of intoxicant in the breath sample.

The ambient detection unit comprises one or more ambient sensors, each ambient sensor mounted inside a cabin of the vehicle and arranged for continuously measuring an ambient concentration of intoxicant in ambient air inside the cabin.

A controller is communicatively connected to an engine of the vehicle and to each of the breath detection unit and the ambient detection unit. The controller is arranged for allowing the engine to be started when determining that the breath concentration is lower than an allowable concentration.

While the engine is running, the controller is arranged for performing the steps of: (1) retrieving, from each of the one or more ambient sensors, a measurement value representative of the actual concentration of intoxicant in the ambient air in the cabin; (11) normalizing each measurement value by scaling with a predetermined baseline value; (in) comparing each normalized value to a respective threshold value; and (iv) in response to determining that at least one of the normalized values exceeds the respective threshold value, generating an alert signal.

The threshold value(s) of the normalized concentration of intoxicant in the ambient air may be based on an allowable blood alcohol content (BAC) value, or may be set independently e.g. as part of a zero- tolerance policy. Preferably the alert signal is generated when the threshold value is exceeded at least three times within a predefined time period.

In contrast to prior art alcohol interlock devices, e.g. using only a breathalyzer device, the system disclosed herein provides a more robust and reliable approach to combating driving offenses related to intoxicants, such as alcohol or other substances that affect the driver's decision making,

responsiveness or perception of traffic, while considering the limitations encountered in previous implementations. The present system incorporates advanced features, including an ambient detection unit that provides a comprehensive assessment of the driver's condition while operating the vehicle. This comprehensive assessment ensures greater accuracy in detecting intoxicant impairment compared to conventional breathalyzer devices. Furthermore, the system offers flexibility by allowing customization of sensor combinations to suit different vehicle types and situational requirements.

By continuously measuring the concentration of intoxicant in the ambient cabin air, the driver's sobriety can be monitored throughout their journey, reducing the likelihood of undetected alcohol consumption while driving. By employing continuous measurement and multiple sensors, the likelihood of detecting any attempts to tamper with or manipulate the system is increased. This aspect serves as a powerful deterrent, reinforcing compliance with regulations and promoting safer driving practices.

In conventional alcohol interlock devices that only make use of a breathalyzer, the driver may tamper with the device by persuading a sober person to blow into the breathalyzer and provide a breath sample, enabling the vehicle to start. Another potential tampering scenario occurs when an intoxicated person attempts to retake a breathalyzer test after failing one, e.g. hoping to lower the detected alcohol level by waiting a short time before reattempting the test. By continuously measuring the intoxicant concentration in the ambient cabin air, the system disclosed herein incorporates a solution to detect and counteract such attempts.

The one or more ambient sensors continuously monitor the vehicle's cabin air for traces of intoxicant during the journey. Consequently, even if a sober individual initially passed the breathalyzer test, the presence of an intoxicated person (the driver) inside the car can be detected by these passive sensors. This continuous monitoring serves as a safeguard against attempts to trick the initial breathalyzer test, maintaining the device's integrity and efficacy in preventing alcohol-impaired driving.

By continuously monitoring the ambient intoxicant concentration, e.g. while the engine is running, the likelihood of undetected alcohol 5 consumption while driving can be detected in a reliable fashion. The continuous monitoring also increases the likelihood of detecting any attempts to tamper with or manipulate the parts of the disclosed system, which in turn reinforces compliance with regulations and promoting safer driving practices.

The generated alert signal may provide a warning message, e.g. a visual or audio message, that may contain instructions for the driver to deter continued driving to reinforce compliance with regulations and safe driving practices. The warning message may e.g. be provided on the dashboard of the vehicle, or on an interface of the system. The warning message may instruct the driver to stop the vehicle or to retake the breathalyzer test which creates the opportunity to analyze if the driver is sober enough to participate in traffic. Optionally, an alarm can be activated if the driver does not respond to the warning message or continues driving.

It 1s possible that the driver does not realize a warning message has been given, therefore an additional alarm might be necessary to notify the driver.

The alarm can be an audio, visual, and/or tactile signal. The alarm can for example comprise honking horns, flashing lights, and/or vibrating the steering wheel of the vehicle. Alternatively, or additionally, the alert signal may be logged on the computer readable storage medium, from where it may be transmitted to a local authority such as the police, to inform that the vehicle is or was driven by an intoxicated driver. The logged data can for example be wirelessly transmissible, e.g. using a WiFi, Bluetooth or NFC communication protocol, or may be transmissible via a removable storage medium or a wired connection.

In some embodiments, for each of the one or more ambient sensors, the controller is arranged for continuously retrieving measurement values over time, and for logging the retrieved measurement values on the computer readable storage medium, and the step of comparing the normalized signal comprises one or more of: calculating a mean of the logged normalized values; calculating a standard deviation of the logged normalized values; and calculating an entropy of the normalized signal; wherein the controller is arranged for generating the alert signal in response to determining that one or more of the calculated mean, standard deviation, and entropy exceeds a respective first, second and third threshold value. Preferably, the alert signal is generated when at least one of the first, second or third threshold value is exceeded at least three times within a predefined time period, e.g. a time period of 10 minutes or less, preferably a time period of 5 minutes or less, e.g. a time period of about 3 minutes, 2 minutes, or 1 minute, to avoid inadvertent triggering of the alert signal.

The mean value, e.g. over a number of historic measurement values, can be used as a low pass filter to prevent the controller responding to outliers in the measurement value, which outliers may exceed the threshold value without being representative of the state of intoxication of the driver. Instead of a mean value, other values based on historic measurement data can be used, such as a running average, a median, a root mean square, or an interpolated value. For similar reasons, the standard deviation of the measurement values can be used. The entropy of the measurement values, e.g. Shannon entropy, can be regarded as the average level of variation, or uncertainty inherent to the variable's possible outcomes. The entropy can be determined using known probability calculation techniques. In the case where certain measurement values dominate, e.g. occur more frequently, such as a skewed probability distribution, there is less surprise and the distribution may have a lower entropy. In the case where no measurement value dominates another, such as equal or approximately equal probability distribution, a larger entropy may be observed. In other words, if the retrieved measurement values are not surprising the entropy is relatively low, whereas a set of surprising measurement values provide a higher entropy. Hence by analyzing the entropy, the reliability of the measurement can be determined.

To accommodate for different types and sizes of vehicles, the predetermined baseline value is dependent on a volume of the cabin. For example, the cabin volume of a truck may be different from the cabin volume of a bus, van, or passenger car. Even within the same type of vehicle, cabin volumes may differ between brands and models. Preferably, the baseline value is obtained by installing the system in the cabin of a specific vehicle, and performing a reference measurement with each of the one or more ambient sensors. In other words, the predetermined baseline value may be associated with a specific vehicle cabin, and a specific configuration of the system as installed in the cabin. The reference measurement may be performed while the vehicle is parked and the engine is switched off, and without any people in the cabin. Preferably, all doors and windows are closed, and the air conditioning unit and heating are switched off to create a static environment in the cabin. For each ambient sensor, the obtained baseline value may be stored such that it can be retrieved by the system at a later time, e.g. on an internal storage medium or a cloud server. For example, the reference measurement(s) may be stored in a lookup table.

To limit the number of false positives, the controller is preferably arranged for generating the alert signal in response to determining that within a predefined time period more than one, e.g. two or three, preferably more than three, of the normalized values exceed the respective threshold value. In other words, only after determining that the threshold value is exceeded multiple times within a predetermined time frame, the alert signal is generated. This prevents that the alert signal is generated in response to a measurement error, or in response to a single outlier value.

The predefined time period can for example be in a range between one and five minutes, preferably between two and four minutes. The lower bound of this range may be set to reduce the number of false positives, while the upper bound of this range may be set according to the expected minimum drive time per trip of the vehicle. For example, if the majority of drives (i.e. trips) of the vehicle takes more than ten minutes, a time period between one and five minutes allows the system to reliably monitor intoxication of the driver in the majority of drives.

In preferred embodiments, the controller is arranged for retrieving measurement values from each of the one or more ambient sensors at a regular frequency. For example, the frequency is between once per second and once per two minutes. A high frequency may increase the accuracy of the monitoring. However, a lower frequency may suffice in practice to provide a reliable indication of the driver’s level of intoxication. Preferably, measurement values are retrieved with an interval ranging between 10 seconds and one minute, more preferably between 20 and 40 seconds, e.g. an interval of about 25, 30, or 35 seconds. This provides a reliable monitoring of intoxication while minimizing data transfer, processing, and/or storage.

In some embodiments, the system further comprises an air sensor mounted inside the cabin and arranged for measuring one or more of a humidity, a barometric pressure and a temperature of the ambient air, wherein the controller is arranged for adjusting the threshold value based on measurements from the air sensor. For example, when the driver opens a window of the vehicle, or activates the air conditioner of the vehicle, the changed conditions of the cabin air can be detected. In this way, any effects caused by changes in air pressure, temperature or humidity, each of which may affect the measured concentration of intoxicant in the cabin air, can be accounted for when monitoring the driver’s level of intoxication.

Preferably, the ambient detection unit comprises at least two ambient sensors, wherein at least one of the ambient sensors is mounted at or near a steering wheel of the vehicle, and wherein the controller is arranged for determining the threshold value based on a respective distance of each ambient sensor with respect to the driver. By mounting at least one of the ambient sensors at or near the steering wheel, said ambient sensor is relatively close to the driver and can therefore measure a concentration of intoxicant in a part of the cabin air in which the driver regularly exhales.

More than one ambient sensor may be mounted at or near the steering wheel, e.g. on the dashboard behind the steering wheel, on the center console, on the roof panel near the rear view mirror, and/or on the A-style frame part between the windscreen and the side window on the driver’s side of the cabin. Air exhaled by the driver when operating the vehicle has a large chance of passing towards or along these ambient sensor mounting positions. One or more further ambient sensors may also be mounted at or near the front and/or rear passenger side of the cabin, to determine whether a concentration of intoxicant in the air around the passenger. In this way, it can be detected when, rather than the driver, a passenger in the cabin is intoxicated and thus influences the concentration of intoxicant in the ambient air inside the cabin. The one or more further ambient sensors can e.g. be mounted to a portion of the dashboard at the passenger side of the cabin, next to the driver's side, to an A-style frame part between the windscreen and the side window on the passenger side, or to the cabin door on the passenger side. Alternatively, or additionally, one or more further ambient sensors may be mounted in the rear of the cabin, around a backseat of the vehicle, e.g. to the roof panel, near the rear doors, or to the rear side of the front seat(s). Accordingly, a concentration mapping of the cabin can be made, from which the controller can be arranged to determine the source(s) of the measured concentration of intoxicant in the cabin air.

For example, in some tampering scenarios the vehicle's windows are left open and the air conditioning (AC) is running at full capacity. Both of these factors may influence the concentration of intoxicant in the vehicle's interior environment and potentially interfere with the system’s accurate detection of intoxicant levels. The influx of fresh air and the air circulation caused by the AC system may potentially dilute the concentration of alcohol within the vehicle. The system disclosed herein effectively takes these factors into account. By strategically placing the ambient sensors, the influence of open windows and AC on the device's alcohol detection capabilities can be mitigated. For example, by mounting ambient sensors at a distance from the cabin windows, the measurements are less affected by variations in environmental conditions. Hence, even with open windows during parts of the drive, the system remains capable of detecting traces of intoxicant, such as alcohol, within the cabin throughout the journey.

Other potential tampering scenarios include the effects of exposure to gasoline fumes at a gas station, or smoke within the vehicle. These substances may potentially produce false positives and/or false negatives. It is found that gasoline fumes from a gas station do not cause an unexpected spike in the sensor readings. This means that the device's ability to detect alcohol remains undisturbed even in the presence of gasoline fumes, adding another layer of reliability to our system. In the context of smoke within the vehicle, tests demonstrated that the system is able to accurately detect the presence of alcohol, and other intoxicants. The system maintains its robustness and sensitivity despite being exposed to smoke.

In general, the one or more ambient sensors and further ambient sensors may be mounted inside the cabin as an add-on to an existing cabin interior, e.g. screwed or glued to the interior, such that the system can be retrofitted in existing vehicles. Alternatively, the one or more sensors may be integrated in the cabin interior, e.g. inside the dashboard and/or cabin lining and panels, such that the sensors are embedded to reduce the risk of tampering with the system.

In some embodiments, for each of the at least two ambient sensors, the controller is arranged for assigning a weight factor to the retrieved measurement values, wherein the weight factor is based on the respective distance of the each ambient sensor with respect to the driver. For example, a relatively high weight factor may be assigned to an ambient sensor located at or near the steering wheel, e.g. with a relatively short distance to the driver and in the driver’s direction of breathing, because it is expected that its output correlates with a level of intoxication of the driver. In contrast, other sensors located farther away from the driver, e.g. at or near a passenger side of the cabin, may be assigned with a relatively low weight factor.

Preferably, each of the one or more ambient sensors provides an analog output signal, e.g. an output voltage proportional to the measured concentration of intoxicant. The output voltage may e.g. continuously vary between 0-5 V, corresponding to situations where no intoxicant is detected, and where a maximum amount of intoxicant is detected, respectively. By providing an analog output signal, any intermediate values of intoxicant concentration can be retrieved by the controller, processed during the steps of normalizing, comparing to a threshold, in order to determine whether the alert signal is to be generated. The analog output signal allows the controller to determine trends of the measured concentration and outliers.

This may be more difficult with discrete ambient sensors that provide a binary output, such as either 0 V or 5 V. The one or more ambient sensors can be used for performing both the baseline, e.g. reference, measurement as well as the continuous measurement of the sobriety of the driver. This may be important to reinforce compliance with regulations and safe driving practices while the vehicle is being operated. The analog sensors allow continuous monitoring of the concentration of intoxicant in the ambient cabin air. The output voltage of the analog sensor may increase with

Increasing concentration.

In some embodiments, the controller is arranged for generating the alert signal in response to determining that the normalized value 1s constant over a predefined period of time. Such a constant signal may be indicative of a failure of the system, e.g. of the controller or at least one of the ambient sensors, or may be indicative of the system being tampered with. For example, the driver may purposely cover or obstruct one or more of the ambient sensors during the readings, e.g. using tape, or damage the sensors, in an attempt to alter the functioning of the system. The controller may be arranged for interpreting the resulting measurement over time as “abnormal”, and generate the alert signal accordingly. Accordingly, the system is capable of detecting a "flatlining" or constant reading, which may be indicative of a tampered or obstructed sensor. Also, a driver may potentially tamper with the device by blowing into the sensors with a face mask on, which may potentially disperse or dilute the expelled breath, making the intoxicant concentration more difficult to detect. Test results indicated that, despite the mask, the system is able to accurately detect the presence and concentration of alcohol in the ambient cabin air. This suggests that the ambient sensor system and algorithms effectively handle the dispersion or dilution effects a face mask might introduce. Furthermore, it underscores its robustness against potential tampering methods while maintaining reliable and accurate readings.

Another potential form of tampering involves cutting the wires connected to the one or more ambient sensors. This scenario represents a more aggressive attempt to bypass the system, aiming to physically disconnect the sensors and thus disrupt the system's ability to detect the presence of alcohol and other intoxicants. To counteract such attempts, the system may monitor the pattern of values provided by the one or more ambient sensors, with a normal operation reflected in a dynamic and varying pattern. If a wire is cut, the corresponding sensor's input to the system will be interrupted, resulting in a different pattern. By monitoring the pattern of measurement values, the system can effectively identify disruptions. This detection capability allows the system to identify wire cutting attempts, promptly triggering the necessary countermeasures to prevent operation of the vehicle.

Preferably, the threshold value is set independently from environmental conditions, physiological traits of the driver, and the dimensions of the cabin of the vehicle. For example, the normalized measurement values may be compared with fixed minimum threshold value, e.g. to establish a zero tolerance policy.

However, in some embodiments, the system further comprises an identification unit arranged for determining an identity of the driver, and the controller may be arranged for determining the threshold value based on the determined identity of the driver. In this way, the threshold value can be individualized, e.g. specifically set for each person. For example, the identification unit may be arranged for scanning an ID of the driver, such as a driver’s license or passport, e.g. using NFC, to verify the identity of the driver. The identity may be coupled to physiological properties of the driver which may affect the threshold value, such as the driver's gender, length, and/or weight. For example, a large male driver may be more tolerant to intoxicant substances, such as alcohol, than a small female driver. Also, past behavior of the driver may be coupled to the ID. For example, in case of recidivism, or earlier reckless behavior of the driver, the threshold value may be specifically lowered for that person.

Also, the threshold value may be determined on the basis of the type and size of vehicle that is to be driven. For example, the threshold value may be lowered for a driver of a bus, or heavy duty vehicle, where the risk of harming passengers and/or other traffic participants is high.

In preferred embodiments, besides the ambient detection unit described herein, the system further comprises a breath detection unit, e.g. “breathalyzer”, arranged for receiving a breath sample from the driver and for measuring a breath concentration of intoxicant in the breath sample, wherein, in response to generating the alert signal, the controller is arranged for requesting the driver to provide a breath sample to the breath detection unit. The driver may be prompted to provide a breath sample to the breathalyzer for determining whether or not the driver is authorized to start the engine of the vehicle, or after driving for a certain period of time, whether the driver is allowed to continue operating the vehicle. Any measurements of the breathalyzer are not necessarily linked to the continuous measurements of the ambient detection unit, as they concern different volumes of air, and thus different levels of concentration. When the breathalyzer detects a concentration of intoxicant in the breath sample that is higher than an allowable concentration threshold, this may indicate that the driver is intoxicated beyond an acceptable level considered safe for participation in traffic. Compliance with regulations and safer driving practices may be reinforced by the controller preventing the engine from being started if the system determines that the driver is not sober enough to participate in traffic.

Additionally, or alternatively, the system further comprises an accelerometer configured to detect movement of the vehicle, wherein, after generating the alert signal, the controller is arranged for activating an alarm in response to the accelerometer detecting movement of the vehicle.

Accordingly, when the driver does not respond to the alert signal and continues to operate the vehicle after it is detected that the ambient concentration of intoxicant is too high, the system may activate an alarm, e.g. a sound or visual alarm.

Other aspects of the invention relate to a method for continuously monitoring intoxication of a driver of a vehicle. The method comprises the steps of: measuring, using one or more ambient sensors mounted inside a cabin of the vehicle, an actual concentration of intoxicant in ambient air inside the cabin; retrieving, from each of the one or more ambient sensors, a measurement value representative of the actual concentration of intoxicant in the ambient air in the cabin; normalizing each measurement value by scaling with a predetermined baseline value; comparing each normalized value to a respective threshold value; and in response to determining that at least one of the normalized values exceeds the respective threshold value, generating an alert signal.

In some embodiments, the method further comprises the steps of: logging the normalizes values in time; calculating a mean of the logged normalized values; calculating a standard deviation of the logged normalized values; and calculating an entropy of the normalized signal; wherein the alert signal is generated in response to determining that one or more of the calculated mean, standard deviation, and entropy exceeds a respective first, second and third threshold value.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further elucidated in the figures:

FIG. 1 schematically illustrates an embodiment of the system described herein;

FIG. 2 schematically illustrates another or further embodiment of the system, comprising two ambient sensors;

FIG. 3 schematically illustrates another or further embodiment of the system, comprising an air sensor;

FIG. 4 schematically illustrates another or further embodiment of the system, comprising five ambient sensors;

FIG. 5 schematically illustrates yet another embodiment of the system;

FIG. 6 schematically illustrates an embodiment of the method described herein;

FIG. 7 illustrates an exemplary set of (normalized) measurements obtainable by the system and method disclosed herein.

DETAILED DESCRIPTION

The invention is described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown.

In the drawings, the absolute and relative sizes of systems, components, layers, and regions may be exaggerated for clarity. Embodiments may be described with reference to schematic and/or cross-section illustrations of possibly idealized embodiments and intermediate structures of the invention. In the description and drawings, like numbers refer to like elements throughout. Relative terms as well as derivatives thereof should be construed to refer to the orientation as described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the system be constructed or operated in a particular orientation unless stated otherwise.

According to the invention, an ambient detection unit, comprising one or more ambient sensors mounted inside the cabin, is continuously monitoring, e.g. in real-time, a concentration of intoxicant in the ambient air inside the cabin. Intoxicant in this context generally refers to any kind of substance that may impact the driving skills of the driver and/or influence their participation in traffic, such as alcohol, cannabis, opioids and other intoxicating substances. The intoxicant may have an effect on the reaction speed and/or capacity of the driver. It is also possible for the intoxicant to influence the width and/or depth of their focus and/or attention. A different example may be an influence on their alertness, whereby the intoxicant may make the driver drowsy and/or fall asleep. The substance can include, but not limited to, different types of alcohol, drugs, medicines, and/or any other substance that may impact the driving skills and/or participation of the driver in traffic. For example for some medicine it is known that they cannot be used while driving, and in those cases it is mentioned on the disclaimer and/or instructions for use of the medicine. Another example is alcohol, for which it is known it can impact how a driver participates in traffic.

A controller is arranged for retrieving measurement values from each of the one or more ambient sensors, and for normalizing the measurement values. The measurement values of the ambient sensors represent the ambient concentration of intoxicant in the ambient air of the cabin. Each measurement value is normalized by scaling it with a predetermined baseline value. The baseline value may for example be the initial value of the corresponding measurement at the time of installing the sensor in the cabin. The (normalized) measurement values can be logged and the time-evolution of the measurement value can be used for further calculations. Such calculations may include, but not limited to, the mean, the standard deviations, the entropy, root mean square, confidence intervals, and/or expected values. These calculated values can be compared to a corresponding threshold value and alerts may be generated if a calculated value exceeds a corresponding threshold value. The threshold value may be set by taking one or multiple different factors into account.

Such factors may include the type of the corresponding measured value, but also the physical traits of the driver, such as their height, weight, gender.

Another set of possible factors may be past behavior of the driver such as their driving history, number of years since their last infraction, number of years since their last accident, and/or possible history of substance abuse.

Preferably, the measurement values are retrieved from each of the one or more ambient sensors at a regular frequency, e.g. at a regular time interval between retrieval of subsequent measurement values from each ambient sensor. This time interval may also be variable. Preferably, the interval between retrieved measurement values ranges between 10 seconds and one minute, more preferably between 20 and 40 seconds, e.g. an interval of about 25, 30, or 35 seconds. The retrieval of measurement values can also be biased to retrieve more values during a specific time period. For example, the controller may be arranged for adjusting the frequency at which the measurement values are retrieved. For example, the frequency may temporarily be increased, e.g. in a certain period of time just after the engine of the vehicle is started, and/or upon determining that measurement values are trending towards the threshold value. Conversely, the frequency may temporarily be decreased, e.g. when the controller determines that, over a certain period of time, the retrieved measurement values follow a steady, predictable pattern.

The controller is arranged for normalizing the measurement values retrieved from each of the one or more ambient sensors, by scaling each measurement value with a baseline, or reference value, which may be obtained with the same ambient sensor. Preferably, the controller is arranged to generate an alert signal if more than one, preferably more than three, of the normalized measurement values exceed the corresponding threshold value in a predefined time period. The number of false positives can be limited by considering multiple normalized measurement values within a predefined time period, because this prevents the generation of an alert signal due to a single measurement error and/or outlier value. The predefined time period may be in a range of one and five minutes, preferably between two and four minutes. The lower bound may be set to reduce the number of false positives, as a larger time period minimizes the influence of a single measurement error and/or outlier value. The upper bound may be set according to the expected drive time per trip of the vehicle. This prevents the situation in which an alert signal cannot be given due to the trip being too short.

The predefined time period can be a rolling time period, for example a six minute drive with a predefined time period of three minutes,

can have more than just two sets of a three minute predefined time period within that drive. A rolling time period may better reflect and monitor the continuous possibility of a changing intoxicant concentration in the air.

The predefined time period may be constant during a trip, but it may also be variable. The predefined time period may for example be shortened during the journey when the system notices that measurement values and/or calculated values are trending towards a threshold value which may be a signal that the driver is slowly becoming intoxicated and might be unfit to participate in traffic. A shorter predefined time period may lead to a faster generation of an alert and instruction of the driver to pullover, to enable a re-evaluation of the sobriety of the driver. The predefined time period may also be lengthened if for example the system notices that the relevant values are trending away from the threshold value, or if the system gave a false alert. A subsequent lengthening of the predefined time period during that journey may lead to a higher accuracy and therefore less false alerts.

Now, turning to the figures, FIG. 1 schematically illustrates a cabin 50 of a vehicle, in particular a passenger car, in which an embodiment of a system 1000 for continuously monitoring intoxication of a driver of the vehicle is installed. Instead of a passenger car, the system may also be installed in the cabin of any other types of vehicle, such as trucks, buses, utility vehicles, etc. The system 1000 comprises a breath detection unit 1.

The breath detection unit 1 may comprise a breathalyzer device, and is arranged for receiving a breath sample from the driver and for measuring a breath concentration of intoxicant in the breath sample. The intoxicant may be any kind of substance that negatively alters the driver’s ability to participate in traffic and comply with safety regulations. Examples of such substances may be medicine, drugs, and/or alcohol. The breath detection unit 1 may comprise a digital or an analog concentration sensor arranged for measuring the concentration of intoxicant in the breath sample. The output of such a concentration sensor may be binary, having only two possible output levels—high level (“1”) or low level (“0”), to signal if the 1ntoxicant concentration in the breath sample is either above or below a threshold value. Alternatively, the output may comprise an analog or discrete signal containing information in the continuous variation of the signal with respect to time.

A controller 3 is communicatively connected to the breath detection unit 1 and is arranged to start the engine if the measured concentration of intoxicant in the breath sample is lower than an allowable threshold value.

In other words, the driver is not able to start the engine when the measured concentration of intoxicant in the breath sample is higher than the allowable threshold value, indicating that the driver's level of intoxication is too high to safely operate the vehicle.

An ambient detection unit is mounted inside the cabin of the vehicle, comprising one or more ambient sensors 2 for measuring a concentration of intoxicant in the ambient air inside the cabin. In the exemplary embodiment of the system illustrated in FIG. 1, one ambient sensor 2 is mounted inside the cabin of the vehicle, near the steering wheel.

More than one ambient sensor 2 may be provided, e.g. two, three, four, five, or even more. Ambient sensors 2 may be mounted at various locations inside the cabin of the vehicle, e.g. on the dashboard, near the seats, near the headrests, on the roof panel, and/or near the door. Each ambient sensor 2 is arranged for continuously measuring an ambient concentration of intoxicant in ambient air inside the cabin.

While the engine is running, the controller 3 is arranged for retrieving a measurement value from each of the ambient sensors 2, normalizing each measurement value by scaling it with a predetermined baseline value, and comparing the normalized value to a respective threshold value, and if at least one of the normalized values exceeds the respective threshold value, generating an alert signal. The predetermined baseline value can be the measured value at the time of installing the system in the vehicle. The baseline value can for example be dependent on the volume of the entire vehicle and/or the cabin of the vehicle.

In some embodiments, the controller 3 is arranged to retrieve and log the measurement values on a computer readable storage medium, such as a hard drive, a solid state drive, and/or a SD-card. The controller 3 may be arranged for processing the logged measurement values. For example, the controller may be arranged for calculating an indicator value such as a mean, a running average, a root mean square, a standard deviation, and/or an entropy of the logged measurement values over a certain period of time.

A threshold value may be set for each type of indicator value. The controller may be arranged to generate an alert if one or more of these calculated indicator values exceed the respective threshold value.

In other or further embodiments the controller 3 may be arranged to only generate an alert signal if multiple measured and/or calculated values exceed their corresponding threshold values, e.g. within a predefined time period. For example the controller 3 may be arranged to generate an alert signal if more than one, preferably more than three, of these values exceed their respective threshold values within the predefined time period.

The predefined time period may be in a range between one and five minutes, or a smaller range, e.g. between two and four minutes.

The alert signal generated by the controller 3 may comprise a warning message such as a visual or audio message, that may contain instructions for the driver to safely pull over. The warning message may be provided on the dashboard of the vehicle, on an interface of the system, and/or projected on the window. By instructing the driver to safely pull over, an opportunity is created for the driver to provide another breath sample to the breath detection unit 1 and to determine if the driver is sober enough to participate in traffic. In some embodiments the system comprises an accelerometer that is configured to detect movement of the vehicle,

specifically after an alert signal has been given. The controller 3 may be arranged to activate an alarm in response to the detection of movement by the accelerometer. The alarm may be an audio, visual, and/or tactile signal.

Examples include, but are not limited to, honking horns, flashing lights, and/or vibrating steering wheel. In another embodiment, the controller 3 might be arranged to log the event of the driver ignoring the warning and/or alarms on a computer readable storage medium. The logged events may for example be used during an evaluation of the driver to determine if the driver complies with safety regulations.

FIG. 2 schematically illustrates another or further embodiment of the system, comprising an ambient detection unit comprising two ambient sensors 2, one mounted near a passenger’s seat and one mounted near a driver's seat. The controller 3 may be arranged for retrieving measurements from each of the ambient sensors at a regular frequency. The frequency may vary depending on the situation. For example, the frequency may be between once per second and once per two minutes. Higher frequencies may increase the accuracy of the monitoring, but a lower frequency may be sufficient to reliably determine the state of the driver. The frequency of retrieving measurement may have a constant time interval between retrieval, but it may also be varied. The frequency of retrieval can also be biased, for example maintaining a higher frequency after providing a breath sample or if the system has determined that a normalized value is trending towards a threshold value. Preferably an interval between measurements retrieved from each of the ambient sensors ranges between 10 seconds and one minute, more preferably between 20 and 40 seconds, for example 25, 30, or 35 seconds.

In some embodiments the controller 3 is arranged to determine a threshold value based on the distance between an ambient sensor 2 and the driver. For example in FIG. 2 the controller may determine a different threshold value for the different ambient sensors 2 since each sensor has a different distance to the driver. In another embodiment the controller 3 may be arranged to assign a weight factor to the retrieved measurement values, based on the distance between the ambient sensor and the driver. By assigning different weight factors to different sensors based on factors such as the distance to the driver, the occurrence of false alerts can be minimized.

A higher weight factor may be assigned to ambient sensors 2 that are closer to the driver to emphasize the measurement values. For example, the weight factor assigned to an ambient sensor mounted in the cabin near a passenger can be relatively small compared to a weight factor assigned to an ambient sensor mounted near the drive, to minimize the number of false alerts given as a response to an intoxicated passenger.

FIG. 3 schematically illustrates another embodiment with an ambient detection unit comprising two ambient sensors 2 mounted at different locations, and additionally comprising an air sensor 4. The air sensor 4 may be mounted at various locations inside the cabin. Examples include, but are not limited to, the dashboard, near the steering wheel, near a car seat, on the ceiling, and/or near the rear view mirror. The air sensor 4 is arranged to at least measure one or more of a humidity, a barometric pressure, and a temperature of the ambient air. Preferably, the controller 3 1s communicatively connected to the air sensor 4 and arranged to adjust the threshold value based on measurements from the air sensor 4. In another embodiment the measured values of the air sensor may be normalized by scaling it with a predetermined baseline value. The baseline value may for example be one or more of a humidity, a barometric pressure, and a temperature of the ambient air at the time of installing the system in the car. These measured values can also be logged on a computer readable storage medium and made available for calculations. The calculations can include, but not limited to, the mean, the standard deviation, and/or the entropy. The controller 3 may be arranged to use these measurements to determine if the system has been tampered with. For example sudden changes in the condition of the cabin can be detected and taken into account.

Sudden changes may for example be windows that are opened, turning on the air conditioning, and/or spraying an aerosol.. The system may also comprise an identification unit (not shown) for determining an identity of the driver. The identification unit may determine the identity of the driver by scanning personal documents such as a driver's license, an identity card, or perhaps a specific card with a unique identification number. The identification unit itself may for example be an NFC reader and/or a barcode scanner. Accordingly, the controller 3 may be arranged for determining the threshold values based on the identity of the driver. The identity of the driver may inform the system of possible traits the driver might have that may influence the determination of the threshold values such as, but not

Limited to, their height, weight, gender, driving record, and/or behavioural record. In an embodiment the ambient sensors 2 provide an analog output signal. In other embodiments the ambient sensors 2 provide a digital output signal with a sampling rate of at least 1 Hz, preferably more than 10 Hz, to provide sufficient data points.

FIG. 4 schematically illustrates another embodiment with an ambient detection unit comprising five ambient sensors 2 of which four are near a driver's seat and one is near a passenger’s seat. At least one of the ambient sensors 2 is mounted at or near a steering wheel of the vehicle. As a result, the distance between this ambient sensor 2 and the driver 1s small and allows for a better measurement of the intoxicant concentration in the breath of the driver after exhalation. Different numbers of ambient sensors 2 may be provided, wherein the ambient sensors are mounted at other locations inside the cabin. The number of ambient sensors 2 and also the ratio of sensors near the driver, and sensors near the passengers may be adapted in dependence of the desired accuracy of the system and/or the total cost of the entire system. A larger number of sensors may lead to a better accuracy and reliability of the system, but may also increase the cost of the overall system. Fewer sensors may lead to a more affordable system, at the cost of decreased performance. The number of ambient sensors 2 may also be adapted in dependence of the internal volume of the cabin. A larger volume may require a larger number of ambient sensors 2 to accurately determine the concentration of intoxicant in the ambient cabin air, and thus the level of intoxication of the driver.

FIG. 5 schematically illustrates another embodiment of the system, further comprising an engine lock 4, arranged for preventing the engine of the vehicle to be started when a breath sample concentration measurement performed with the breath detection unit 1 exceeds an allowable threshold value. The control unit 3 is operative connected to the engine lock 4.

Ambient sensors 2 are provided at various locations inside the cabin, such as near the rear view mirror, near the A-style chassis frame member on the driver and passenger side of the vehicle, and centrally on the dashboard. Preferably, the controller 3 is arranged to generate an alert and/or a warning if ambient sensors 2 show irregular behaviour that may imply tampering of the system, e.g. upon detecting that the normalized value is constant over a predefined time period. Tampering efforts such as cutting wires, and/or obstructing a sensor, may result in such irregular behaviour.

FIG. 6 schematically illustrates an embodiment of a method 100 for continuously monitoring intoxication of a driver of a vehicle, e.g. using the system described herein. The method 100 comprises the steps of:

Step 101: measuring, using one or more ambient sensors mounted inside a cabin of the vehicle, an actual concentration of intoxicant in ambient air inside the cabin.

Step 102: retrieving, from each of the one or more ambient sensors, a measurement value representative of the actual concentration of intoxicant in the ambient air in the cabin.

Step 103: normalizing each measurement value by scaling with a predetermined baseline value.

Step 104: comparing each normalized value to a respective threshold value.

Step 105: in response to determining that at least one of the normalized values exceeds the respective threshold value, generating an alert signal.

Optionally, the method 100 may comprise other steps. For example, after step 103 of normalizing each measurement value, the method may comprise the steps of logging the normalized values in time. Steps 104 and 105 may be performed by calculating e.g. (i) a mean of the logged normalized values, (11) a standard deviation of the logged normalized values, and (ii) an entropy of the normalized signal. Instead of calculating the values listed in (1)-(@i1) other or more values may be calculated from the historical data provided by the logged normalized values. For example, the calculated values may comprise a median, a running average, a root mean square, a statistical distribution, or an interpolation.

In step 105, the alert signal is preferably generated in response to determining that one or more of the calculated mean, standard deviation, and entropy exceeds a respective first, second and third threshold value.

Preferably, the alert signal is generated in response to determining that at least one of the first, second or third threshold value is exceeded three or more times within a predefined time period, e.g. a time period between 1 and 5 minutes, or between 2 and 4 minutes.

The method 100 may further comprise a step of requesting the driver to provide a breath sample to a breath detection unit. The breath detection unit may measure the intoxicant concentration in the breath sample. The measured intoxicant concentration may be above or below a threshold value. In case the concentration is above the threshold, this may be indicative of the driver being intoxicated. As a result, the engine may be prevented from starting, e.g. by a control unit operatively connected to the engine and the breath detection unit, until a breath sample is provided with an intoxicant concentration lower than the allowable threshold value.

Preferably, after detecting a too high intoxicant concentration, there is a cooldown period in which the breath detection unit does not analyse any further breath samples, e.g. to deter an intoxicated driver from asking a sober passenger to provide a breath sample after the driver failed a breathalyzer test.

Upon determining that the intoxicant concentration is below the allowable threshold value, e.g. indicative of the driver being sufficiently sober, the engine may be allowed to start. While the engine is running, the level of intoxication of the driver is continuously monitored by one or more ambient sensors continuously measuring the concentration of intoxicant in the ambient air inside the cabin of the vehicle. For each ambient sensor measurement values representing the actual concentration of intoxicant in the ambient air in the cabin are retrieved. The retrieved measurements are normalized by scaling them with a predetermined baseline value. Each normalized measurement value is compared to a respective threshold value.

An alert signal is generated if at least one of the normalized values exceeds the respective threshold value, preferably multiple times, e.g. at least three times, or more.

FIG. 7 illustrates an exemplary set of measurement values retrieved from multiple ambient sensors, normalized, and converted to a mean, a standard deviation, and an entropy. Each column contains plots for a different ambient sensor. The first five columns are related to ambient sensors at various locations within the vehicle, such as near the driver, near the center of the dashboard between the drive and passenger side, and/or at the passenger side. The last column is related to an air sensor and in this particular figure, the pressure has been plotted. This situation uses five ambient sensors, and one air sensor. Each row in FIG. 7 relates to a different calculated value. The first row represents the calculated mean of logged measurement values, the second row represents the calculated standard deviation, and the third row represents the calculated entropy. A relatively large mean value associated with an ambient sensor close to the driver may indicate a state of intoxication of the driver. A relatively large standard deviation of the measurement value associated with the same ambient sensor may be indicative of a measurement error or outlier. The calculated entropy value is indicative of the variation of measurement values. A large entropy may indicate a level of intoxication that is too high.

By analysing the different types of calculated values in combination, the reliability of the system can be increased and as a result the number of false alerts can be decreased. Instead of, or in addition to, the mean, standard deviation and entropy, other calculations can be performed with the normalized measurement values in order to compare with a threshold value.

Such other calculations may include a confidence threshold, interpolated or extrapolated values, and/or other computations. Each calculated value may be associated with a threshold value indicative of the driver being intoxicated or sober, depending on the comparison between the calculated value and their respective threshold value.

It will be clear to the skilled person that the invention is not limited to any embodiment herein described and that modifications are possible which may be considered within the scope of the appended claims.

Also kinematic inversions are considered inherent to the invention disclosed herein. In the claims, any reference signs shall not be construed as limiting the claim.

The terms 'comprising' and ‘including’ when used in this description or the appended claims should not be construed in an exclusive or exhaustive sense but rather in an inclusive sense. Thus expression as including’ or ‘comprising’ as used herein does not exclude the presence of other elements, additional structure or additional acts or steps in addition to those listed. Furthermore, the words ‘a’ and ‘an’ shall not be construed as limited to ‘only one’, but instead are used to mean ‘at least one’, and do not exclude a plurality. Features that are not specifically or explicitly described or claimed may additionally be included in the structure of the invention without departing from its scope.

Expressions such as: "means for ...” should be read as: "component configured for …" or “member constructed to ..." and should be construed to include equivalents for the structures disclosed. The use of expressions like: "critical", "preferred", "especially preferred” etc. is not intended to limit the invention. To the extent that structure, material, or acts are considered to be essential they are inexpressively indicated as such. Additions, deletions, and modifications within the purview of the skilled person may generally be made without departing from the scope of the invention, as determined by the claims.

Claims (15)

CONCLUSIONS 1. A system for continuously monitoring the intoxication of a driver of a vehicle, comprising: — a breath detection unit adapted to receive a breath sample from the driver and to measure a breath concentration of intoxicant in the breath sample; — an environmental detection unit comprising one or more environmental sensors, each environmental sensor being mounted in a cabin of the vehicle and adapted to continuously measure an ambient concentration of intoxicant in the ambient air within the cabin; and — a control unit communicatively connected to an engine of the vehicle and to each of the breath detection unit and the environmental detection unit; the control unit being adapted to allow the engine to be started upon detecting that the breath concentration is below a permissible concentration; the control unit being adapted, while the engine is running, to perform the steps of: retrieving, from each of the one or more ambient sensors, a measured value representative of the ambient concentration of intoxicant in the ambient air within the cabin; normalising each measured value by scaling by a predetermined baseline value; comparing each normalized value with a respective threshold value; and upon determining that at least one of the normalized values exceeds the respective threshold value, generating a warning signal. The system of claim 1, wherein the control unit is configured to continuously acquire measurement values from each of the environmental sensors over time and to record the acquired measurement values on a computer-readable storage medium, and wherein the step of comparing the normalized signal comprises one or more of the following: calculating an average of the captured normalized values; calculating a standard deviation of the captured normalized values; and calculating an entropy of the normalized signal; wherein the control unit is configured to generate the warning signal upon determining that one or more of the calculated averages, standard deviations, and entropies exceed a respective first, second, and third threshold value. 3. The system of any preceding claim, wherein the predetermined base value is dependent on a volume of the cabin. 4. The system according to any one of the preceding claims, wherein the control unit is arranged to generate the warning signal upon determining that within a predefined time period more than one, preferably more than three, of the normalized values exceed the respective threshold value. 5. The system according to claim 4, wherein the predefined time period is between one and five minutes, preferably between two and four minutes. 6. The system of any preceding claim, wherein the control unit is configured to retrieve measured values from each of the one or more environmental sensors at a regular frequency. 7. The system of any preceding claim, further comprising an air sensor mounted in the cabin and adapted to measure one or more of a humidity, a barometric pressure and a temperature of the ambient air, the control unit adapted to adjust the threshold based on measurements from the air sensor. 8. The system of any preceding claim, wherein the environmental sensing unit comprises at least two environmental sensors, at least one of the environmental sensors being mounted on or near a steering wheel of the vehicle, and the control unit being adapted to determine the threshold value based on a respective distance of each environmental sensor from the driver. 9. The system of claim 8, wherein the control unit is configured to assign a weighting factor to the retrieved measurements for each of the at least two environmental sensors, the weighting factor being based on the respective distance of each environmental sensor from the driver. 10. The system of any preceding claim, wherein each of the one or more environmental sensors provides an analog output signal. The system of any preceding claim, wherein the control unit is configured to generate the warning signal upon determining that the normalized value is constant over a predefined time period. 12. The system according to any of the preceding claims, further comprising an identification unit adapted to determine the identity of the driver, wherein the control unit is preferably adapted to determine the threshold value based on the identity of the driver. 13. The system of any preceding claim, further comprising an accelerometer configured to detect movement of the vehicle, wherein, after generating the warning signal, the control unit is configured to activate an alarm upon detecting movement of the vehicle by the accelerometer. 14. A method for continuously monitoring the intoxication of a driver of a vehicle, the method comprising the steps of: — measuring, using one or more ambient sensors mounted in a cabin of the vehicle, an actual concentration of an intoxicating substance in the ambient air within the cabin; — retrieving, from each of the one or more ambient sensors, a measurement value representative of the actual concentration of an intoxicating substance in the ambient air within the cabin; — normalising each measurement value by scaling by a predetermined baseline value; — comparing each normalised value with a respective threshold value; and — upon determining that at least one of the normalised values exceeds its respective threshold value, generating a warning signal. 15. The method of claim 14, further comprising the steps of: — recording the normalized values over time; — calculating an average of the recorded normalized values; — calculating a standard deviation of the recorded normalized values; and — calculating an entropy of the normalized signal; — the warning signal being generated upon determining that one or more of the calculated averages, standard deviations and entropy exceed a respective first, second, and third threshold value.