Impaired Driving. Statistical Data Technological Solutions and Recommendations. Submitted the 13 th Mai 2005

Transcription

1 Active Safety Department of Machine and Vehicle Systems Chalmers University of Technology Academic Year 2004 / 2005 Active Safety Report Impaired Driving Statistical Data Technological Solutions and Recommendations Submitted the 13 th Mai 2005 MickaÄl PAUTONIER Kloiravab SONGPON Sylvain LEJEALLE Benoit MEUNIER Tobias DEHLER Xavier BEAUD

2 Abstract Impaired driving is a major cause of car accident fatalities and imposes enormous costs on the society : families, health care, insurance companies and the public in general pay the price for impaired drivers. In order to tackle this issue, researches were and are still going on in the field of active safety. The main concerns of the present report is to define as well as possible the different kind of impairments and their influences on the driving performances. According to these biological analysis, a review of the different technical solutions used today or still in development is presented. A brief overview of their operating and functioning means is generally done. For each kind of impairment and especially if a lack of technical solutions is noticed, recommendations to avoid dangerous situation are given. The report is divided into four parts that constitute four major impairments: drowsiness, alcohol, drug and the effect of age on driving. Each part begins with a background in which some statistics or global presentation of the impairment are given. This background is followed by the review of the technical solutions and recommendations. It turns out through this report that the main technical solutions tackle mostly with drowsiness, drugs being technically difficult to detect except through an induced drowsiness state. Alcohol can be detected and some solutions are studied. Regarding elderly drivers, they might drive with functional deficits, medical problems or under the influence of legal medicine, thus limiting their ability to drive. Recommendations are mostly given in that case. Some solutions which seems to be very efficient to detect impairment are presented in this report. But they are often restrictive for the driver and might not please customers. Therefore even if science is ready to do things to decrease car fatalities, it is not taken for granted that drivers are. 1

3 Table of content Abstract Table of content I Introduction II Drowsiness and driving II.1) Background II.2) How to detect a drowsy driver II.3) Technological solutions II.4) Recommendations III Alcohol and driving III.1) Background III.2) Driving effects of alcohol use III.3) How to detect a drunk driver III.4) Technological solutions III.5) Recommendations IV Drugs and driving IV.1) Background IV.2) Effect of the illegal drugs IV.3) Laws in the different countries IV.4) Technological solutions IV.5) Recommendations V Elderly drivers V.1) Background V.2) Effect of the age on the driving capacity V.3) Effects of medical conditions and medications V.4) When should you stop driving VI Conclusion References Appendices 2

4 I Introduction Road safety is one of the most important problems that car manufacturers, traffic institutes and governments have to deal with. The global cost of road crashes in the highly motorised countries are estimated to 2% of their GNP. That is why a lot of researches in the area of safety are financed by these institutions to reduce the gravity of the crashes, and especially on active safety to simply reduce the number of these same crashes. If all types of impairment are taken into account, impaired-related fatalities represent easily more than 50% of the total fatal crashes. Furthermore, these impairments are often only one of the many causes which have leaded to a crash. Indeed, safe driving requires clear judgment, concentration, and being able to react to what happens on the road. Drowsiness, alcohol, drugs and even age affect all of these, involving decreased driving performances. In order to optimize the traffic safety and minimize the fatalities in road crashes, impaired drivers have to be alerted or excluded from the traffic. Excluding drivers having a long-term impairment, caused for example by chronic sickness or age, is a responsibility of the legislation. But alerting or excluding short-term impairment, caused for example by drowsiness or alcohol, needs technological devices that control the state of the driver over the whole driving process and can inhibit the impaired driver starting the car if needed. One more time, investing in researches on this kind of onboard technologies or in the implementation of safety devices on roads mainly depends on governments priorities. The following chapters address the reasons that cause impairments and summarize the state of the art in technological solutions, that are or can be used to prevent impaired persons from driving or alert them of their physical state. They also discuss advantages and limitations of the different technologies and describe how, when and why the impairments occur. 3

5 II Drowsiness and Driving II.1) Background L1,2,3, WS1,2 a) Drowsiness and fatigue : complex human factors Sleepiness and drowsiness are generally defined as the state where a person is almost asleep or lightly asleep. It refers to an inability to keep awake or a drive to sleep. Fatigue is a consequence of a physical labour and is defined as a disinclination to continue the task. In regard to driving, a psychologically based conflict between the disinclination and the need to drive. Sleep is a neurobilogic need with predictable patterns of sleepiness and wakefulness. It is governed by the circadian pacemaker which is our internal 24 hours body clock. A predictable pattern of sleepiness commonly occurs about 12 hours after the previous midsleep period. That means people who sleep through the night are likely to become sleepy in mid afternoon and just before their usual bedtime. The number of hours of sleep we need each day varies from person to person. To reach their highest level of performance, most people need between 7 and 10 hours in each 24 hours period, with 8 hours being often considered as the norm. If the normal circadian cycle is broken due to restriction, interruption or fragmentation of sleep, the risk of drowsiness during the day is increased a lot. Research into the ability to perform specific vigilance tasks indicates that less than 4 solid hours of sleep per night significantly impairs performances. Moreover, loss of sleep is cumulative. The loss of one night s sleep can lead to extreme short-term sleepiness while habitually reducing sleep by 1 or 2 hours a night can result in a sleep debt and lead to an unexpected chronic sleepiness. Other biological cycles (light/dark, hunger, ), can also lead to drowsiness if they are interrupted. For example the repetitive cycle of light and dark influences our alertness. If this cycle is interrupted, that means a person who is used to sleep during night has to be awake, the results are sleepiness and performance impairment, even if the person have slept enough during the 24 hours before. External conditions have also influences on the state of sleepiness. Studies have shown that drowsiness and hypovigilance frequently occurs during highway driving with low traffic. It is in fact due to the safe feeling of the driver and the monotony of this kind of high quality roads. A simulator study L2 has been carried out by the Transport Research Centre of the University of Montreal to show the influence of the monotony of the road on fatigue. A lot of external factors (weather conditions, traffic, inside temperature, comfort, ) can in the same way favour drowsiness. Some studies about the psychological and physical states of the driver have also been done. After specifically exhausting events, if the driver is ill or if he feels particularly sad, he is more likely to reach the state of drowsiness. Drivers who suffer from sleep disorders (chronic insomnia, sleep apnea, narcolepsy, ) are at particular risk of accidents because those problems lead to excessive daytime sleepiness. These psychological and physical states can be of course highly influenced by the ingestion of medications, alcohol or drugs. But the main factor of drowsiness is still the loss of sleep due to a personal lifestyle choice or a jobrelated sleep time restriction. Indeed the contemporary societies function 24 hours a day and economic pressures increase demands on many people to work instead of sleep. Drowsiness and driving problems become here consequences of the modern way of life and society model. 4

6 L1,6, WS3,4,6,7 b) How drowsiness influences the driving performances Sleepiness involves crashes because it impairs element of human performances which are critical for a safe driving. - Time of reaction The time of reaction is the most influenced by drowsiness human factor. Drowsiness involves of course a slower reaction time and even a small decrement in this parameter can have a profound effect on crash risk, especially at high speed. - Vigilance The Vigilance decreases with drowsiness. Drowsy drivers, as distracted drivers (phone, food, ) are always less vigilant than the others (we talk sometime about hypovigilance ). Performance and attention based tasks decline with sleepiness. It involves an increased delay of respond which has basically the same effect on driving performances than a slower reaction time (See Figure II-1). Faster Normal Inverse of Reaction Time Slower Sleep Deprived Time on Task Figure II-1: Influence of drowsiness on the total reaction time L1 - Information integration Processing and integrating the information is also longer if the driver is subjected to drowsiness. The accuracy of short-term memory decreases and the information can be in a wrong way interpreted. We talk here about impaired judgement which involves of course declined performances but which also can lead directly to a crash. - Micro-sleep and major sleep phenomena If drowsiness becomes too important, a micro-sleep phenomena can occur : the driver fall asleep during 1 to 4 seconds. The driver is often not conscious of these break times during which he receives no information at all. This phenomena can lead directly to a crash if a capital information has not be integrated by the driver. The next level of gravity in drowsiness and driving problems is simply the major sleep! 5

7 L1,2,3,4,5,6, WS5,6,7,8 c) Statistics: drowsy driving experiences and population concerned Drowsy driving is a serious problem that leads to thousands of road vehicle crashes each year. Many studies are done by road institutes all over the world. We will try in the following chapters to summarise the information of these different studies and we will give data graphs from one of the most complete and accurate survey held in USA in 2002 L4. - Experience with drowsy driving The NHTSA study 2002 L4 shows that around 37% of the driving population have nodded off for at least a moment or fallen asleep while driving at some time in their live. 29% of them have last experienced this problem within the past year and 10% within the past month (See Figure II-3). This give a range of 4% of the drivers (that is around 7,5 million drivers in USA) who have nodded off while driving at least one time during only one month. Males (49%) are almost twice as likely to report having nodded off while driving than are female drivers (26%) (See Figure II-2). If young people are often considered as one of the population group at highest risk, it doesn t really appear in this study. Indeed, newer drivers (i.e. those under age 21) who have had less time driving overall, are only half as likely to have experienced nodding off while driving (18%) as older drivers. Figure II-2: Ever nodded off while drivingl L4 Figure II-3: Recency of nodding off at Wheel L4 An other American study made by the National Sleep Foundation WS8 on this topic has quite the same conclusions and reports that 62% of drivers drive while feeling drowsy and 23% have at least one time fallen nodded off. A separate roadside survey WS1 of 593 long-distance truckers found that at least 25% of them had fallen asleep behind the wheel at least once. Other American and European studies L1,5,6 confirm these results. But these studies are based on interview of drivers. So only drivers who were conscious having fallen asleep have reported it. These results are probably underestimated and doesn t include the micro-sleep phenomena. We can conclude that at least 25% and probably not far from 50% of the drivers in the world have fallen asleep behind the wheel at least once. - Influence of the number of hours slept on drowsiness As it has been explained in the chapter II-1)a), the drowsiness is mainly due to the loss of sleep, so the number of hour slept before the driving trip. The NHTSA study 2002 L4 is the only one which permit to give an accurate conclusion about the influence of the number of hours slept on drowsiness. It shows that 24% of the drivers who have reported a drowsiness experience had less 6

8 than 4 hours slept the night before. Only 33% of them had slept at least 7 hours, which can be considered at the lowest level to reach his maximum performances during the day (See Figure II-4 and II-5). For a statistical result showing the influence of the number of hours on the risk of the drowsiness related crash please refer to the graph in Appendix A.1. Drowsy drivers under age of 30 had slept on average 5,5 hours before driving and drowsy drivers over age of 65, 7,7 hours. This result shows that old people are one of the population group at highest risk as they are more likely to nod off even if they have slept enough before. But we should not forget that young people are considered as the population group at highest risk as they often sleep less and underestimate the influence of drowsiness on driving performances. Figure II-4: Hours slept the night before drowsiness L4 Figure II-5: Average time slept the night before L4 As we were expected, the conclusion is that drivers with less than 7 hours of solid sleep time are more likely to be subjected to drowsiness. Population groups concerned are here young people (under 30) and old people (over 65) but for different reasons. - Characteristics of the most drowsy driving trip As it has been said in chapter II-1)a), external factors and especially the road/traffic conditions and the psychological and physical state of the driver can highly favours drowsiness. Many studies L1,2,4,6 have been done to determinate the worst conditions which involve drowsiness. The NHTSA study 2002 L4 considers only few of the many factors which could be considered as having an influence on drowsiness, but the conclusion are quite interesting. It shows that 28% of the drivers reporting a recent drowsy driving experience had this experience during night, between midnight and 6:00am, 35% between 6:00am and 5:00pm and 17% between 5:00pm and 9:00pm (See figure II-6). It also highlights the fact that only 22% of these same drivers were driving for more than five hours and 47% were for one hour or less (See figure II-7 and II-8). This is of course strange results but it shows that the loss of sleep is probably more dangerous than the fatigue due to driving. However we have to be careful when giving a conclusion for these results as the short driving trips are largely more frequent than long ones (more than 5 hours), even in USA where the mean travelling distances are longer than in Europe. On average, these drivers were driving for almost three hours before they nodded off and we can clearly identify old people as a population group at highest risk as they nodded off after less time of driving. The last factor taken in account in this study is the type of road. Here the study show that 58% of the drivers reporting a recent drowsy driving experience had this occurrence on multi-lane highways (See Figure II-9). Combined with the fact that only 55% of the drivers frequently drive on highways, it shows that this kind of road is very favourable to sleepiness. 7

9 Figure II-6: Time of day nodding off while driving L4 Figure II-7: Average time driving before nodding offng L4 Figure II-8: Average time driving before nodding off L4 Figure II-9: Type of road driving on while nodding off L4 Other studies and papers L1,2,6 have quite the same conclusions : driving at night, during long hours without breaks and on highways (monotonous roads) increases the risk of crashes related to drowsiness in high proportions. Explanation of these phenomena can be found in the previous chapter II-1)a). L1,4,6,7,8, WS5,6,7,8,9 d) Statistics: number, importance and costs of the crashes due to drowsiness Studies in USA and Europe show that drowsiness is the fourth accident factor after alcohol, speed and right of way refusal. In USA, it is estimated by NHTSA that between 1 to 4% of the accidents are related to drowsiness, but the National Transportation Safety Board consider that more than 10% of the accidents are related to drowsiness with 28% of them being fatal. Studies from Norway, Australia and Britain have given estimates of 4%, 6% and 16% respectively. One more time these results are underestimated as it is very difficult for the police officers to determine the real causes of a crash. Furthermore, sleepiness is often only one of the many parameters which lead to the crash. The NHTSA WS5 estimates that police-reported crashes annually involve drowsiness or fatigue as a principal cause in USA. Fall-asleep crashes are responsible for roughly 1,500 fatalities every year (about 4% of all crash fatalities) and at least injuries. Sleepiness related crashes are usually severe because drivers who have nodded off are unable to attempt to avoid the crash. NHTSA estimate that the annual cost of these crashes represent 12,5 billion dollars. An other study L7 shows that in Germany this cost is around 1,2 billion dollars and is reduced in Sweden to 0,3 billion dollars. It represents around 0,1% of the GNP in the highly motorised countries. The previous estimations increase if we only consider highways. Studies L1,6 shows that on French highways the crashes related to drowsiness represent around 30% of the total crashes and 40% of the fatal crashes on American highways are due to sleepiness. They also show that 55% percent of the 8

10 drowsy related crashes occurs at night (between midnight and 8:00pm), 81% in straight lines and that in 76% of the case, the driver was the only occupant of the vehicle. L1,4,5,6,7,8, WS4,5,6,7,8 e) Population groups at highest risk In a study made by the state of North Carolina, 55 percent of fall-asleep crashes involved people 25 years old or younger. The overwhelming majority were males (78%), and the peak age of occurrence was 20 years. The NHTSA study 2002 L4 gives quite the same conclusions on the past 5 years (See Figure II-10 and II-11). It is easy to conclude that young people are the population group at highest risk for the crashes related to drowsiness. Indeed, if old people are more likely to nod off behind the wheel, they are conscious of this problem and apply countermeasures. For more detailed statistics about the crashes due to drowsiness by age and time of the day, see the NHTSA report 1998 L1 in Appendix A Figure II-10: Involved in crash as result of nodding off L4 Figure II-11: Estimated number of crashes due to nodding off L4 Other studies L4, WS3 suggest that 20 to 30% of the shift-workers with non traditional schedules had a sleep-related mishap within the last years. They are 2 to 5 time more likely to fall asleep at wheel. Many studies are also dedicated to the professional drivers and especially the truck drivers. Fatigue related crashes constitute 2,7% of all the crashes involving trucks. As these professional drivers stay all day long behind the wheel, they are particularly likely to nod off while driving due to fatigue. That s why they are the only type of drivers to be subjected to laws in different countries regarding the number of driving and sleeping hours. f) Conclusion Sleepiness is the fourth factor of crashes. In most of the cases, drowsiness is not the direct cause of the crash but have reduced significantly the performances of the driver to avoid it. Crashes having drowsiness as main cause represent between 5 and 20% of the total crashes and are generally severe, involving injuries or death. This kind of crashes is more likely to occur during the night, on large highways with low traffic and if the driver is alone in his vehicle. But of course the main causes of drowsiness at wheel are the loss of sleep and the fatigue due to the number of hours driven before. The population group which is more likely to feel drowsiness while driving is old people. But the one having the highest risk of crash related to drowsiness is definitely young males who are more subjected to losses of sleep and are not conscious of it. Shift-worker and people who suffer from sleep disorders are also a population group at high risk as their circadian cycle is often broken. 9

11 II.2) How to detect a drowsy driver L1,3,9,10, WS1,2,3,4 a) Visible behaviours and external physiological parameters As it has been explained before, a drowsy state involve a high decrease of the driving performances. This phenomena can especially be recognized through the time of reaction which tends to increase a lot. This can involve particularly dangerous behaviours, for example the driver vary out of lane and suddenly notice that he is too close to the car ahead and has to brake in emergency. Microcorrections in the steering angles done by the driver to compensate the road imperfections and crosswinds tend also to decrease and the steering movements become larger. This phenomena involves an increased lane tracking variability, that simply means that the driver tends to not follow perfectly his lane, which can be considered as a very dangerous behaviour. A drowsy driving can also be recognized by an increased speed variability and a decreased minimum distance to any lead vehicle. Many electronic systems are used or are going to be used to measure the driving performance according to the previous cited parameters. They are presented in chapter II.3). Other visible physiological parameters which seem to be quite reliable to indicate drowsiness concern ocular dynamics. Five parameters are generally taken in account: the blink duration, the blink frequency, the partial eye closure, the complete eye closure and the saccade frequency. The two last parameters signal micro-sleep or complete nod off phenomenon and studies show that they often precede off-road crashes. The other parameters permit to estimate a level of sleepiness. Some researches on a complete Electrooculogram (EOG) are carried out. This system could permit to add the eye movements and the pupil size to the other cited parameters. The body motions give also parameters which can be related to drowsiness. Indeed, the fatigue due to driving affect the alertness of the driver which makes slower and fewer movements. For example large head and body movements show an obvious indicator of fatigue, and repeated nods forward of the head indicate a micro-sleep phenomenon. These parameters are generally not very reliable as it is very difficult to measure and interpret them in a right way. But they are often used combined with ocular dynamics parameters to give a more accurate estimation of the fatigue level. Yawning is also one the more visible sign of drowsiness. Unfortunately no system is able today to use this parameter to signal to the driver his state of drowsiness. L9,10, WS4,8 b) Internal physiological parameters The brain activity is closely related to drowsiness and electroencephalogram (EEG) can be used to detect it. The amount of activity in different frequency bands can measured, and the stage of sleepiness can be determined thanks to a spectral analysis. Studies L9,10 have shown that it is a very accurate and reliable indicator of drowsiness, but it involves of course an expensive and uncomfortable electronic system. An other internal physiological parameter which could be used to detect drowsiness is the heart rate. A decrease in heart rate and an increase in heart rate variability have shown to be indicators of drowsiness. A decreased production of adrenaline, noradrenaline and cortisol are other possible indicators of drowsiness. 10

12 II.3) Technological solutions a) The PERCLOS monitor L9,10,11 This technology is based on the physiological properties of the human eye. Indeed the retina reflects different amount of infrared light depending on its wavelength. Furthermore, a 850nm wavelength infrared radiation totally passes through the eye, and reflects on the retina. Thus, the image given by an infrared sensitive camera shows a bright pupil (See Figure II-13). On the other hand, an infrared radiation at 950nm wavelength is almost entirely absorbed by the water molecules in the eye, resulting in a dark pupil (See Figure II-12). Figure II-12: Bright pupil image L11 Figure II-12: Dark pupil image L11 Since the only difference between the two images is the intensity of the retinal reflection, subtracting one to another leads to an image on which only the retinal reflection remains (See Figure II-13). Then, the system measures the pupils height, and this value is used to calculate PERCLOS (PERcent eyelid CLOSsure), which is a scientifically validated measure of drowsiness. Indeed, knowing both the instantaneous height of the pupils and the blinking frequency of the eye, it is now possible to make an evaluation of the state of awareness of the driver, and therefore to warn him if needed. To perform this process, the system needs to be composed of two cameras with two different filters, seeing exactly the same image. This is done thanks to a beam-splitter which reflects or transmits the image onto the lens of the two cameras, placed at a 90 degree angle from one another (See Figure II- 14). Figure II-13: Processed image L11 Figure II-14: Set up of the cameras L11 11

13 One of the main advantages of this system is that, if the process is well defined, it could detect a drowsy driver before he put himself, as well as others, in a dangerous situation. Just by measuring the blinking period as well as the height of the pupils, the system should be able to determine whether the driver is able to drive or not and thus alert him, wake him up or give him recommendations. Of course, such a system has to be reliable. Indeed if the driver begins to rely on this system, any failure might lead to an increase in the risk for a crash since the driver will no longer be aware of its drowsiness. It should as well not give many false alarms, otherwise the driver will no longer pay attention to the alerts, even in actual dangerous situations. This system is one of the most reliable and easy to implement drowsiness indicator. Studies have shown that it could give very good results if it is used in a proper way. Indeed, if the driver relies too much on this technology, he might tend to continue driving even if he is conscious of his drowsiness since he will think that the system will be here to wake him up if he falls asleep. b) The Nap Zapper WS12 As it as been said before, the body movements can be considered as an indicator of drowsiness. It is generally a parameter only used to complete the PERCLOS monitor system which can give a more accurate drowsiness level estimation. But recently, a new little device called the Nap Zapper (figure 5 and 6) appeared on the American market. This system is equipped with an electronic position sensor, being thus able to detect any unusual movement of the head. When the head of the driver nods forwards, the system sounds a loud alarm, therefore waking up the driver instantaneously and warning the other occupant of the vehicle. Figure II-15: Nap Zapper WS12 Such a system has the huge advantage of being very cheap, only 15$, and therefore affordable by most of the drivers. It is also a device which has not to be implemented directly in the car. Nevertheless the reliability of this technology has not been proved yet, and it is very likely to give many false alarms. Indeed, any quick movement of the head to look at the radio or the dashboard for example might be interpreted by the system as a sign of drowsiness. If the number of those false alarms tends to be quite large, the driver will simply no longer use the device. c) The Steering Attention monitor L9,11,12 In order to keep a straight trajectory, the driver needs to apply micro-corrections to the steering wheel, to compensate for environmental factors such as crosswinds, and any imperfection in the road. Yet, when a driver starts to be drowsy, the number of those micro-corrections will strongly decrease and the steering movements become lager. Therefore, thanks to a sensor measuring the 12

14 position of the steering wheel, and thus the micro-corrections, the system is able to detect whether a driver is drowsy or not, depending on the frequency of the micro-corrections. If the driver is considered as potentially drowsy, the system will sound an alarm in order to wake him up. One asset of this technology is that it can be quite easily implemented on cars, as compared to some other technologies such as the PERCLOS monitor. As well, this system might not be too expensive, since the main device is a sensor. On the other hand, this technology strongly depends on the road condition and might therefore not be very accurate. Indeed, if a perfectly awake person drives on a straight highway, very smooth, and without any crosswind, the driver should not have to make many micro-corrections to maintain a straight trajectory. Yet the system might consider this lack of micro-corrections as a sign of drowsiness and therefore sound an alarm when not needed. d) Lane Departure Warning System (LDWS) WS10 This system, first implemented on the recent cars of the French manufacturer CitroÖn, is composed of six infrared sensors located within the front bumper and dispatched on both sides of the vehicle. More precisely, each sensor is composed by an infrared-emitting diode and a detection cell. Those sensors are thus able to detect a line just by measuring the difference of intensity of the reflected infrared light. Figure II-15: The system detect a lane departure and alert the driver WS10 Figure II-16: Once the driver is alerted, the car retrieves a normal trajectory WS10 Once activated, the sensors detect any line crossing and if the driver has not put his indicator, the system interprets this situation as potentially dangerous (See Figure II-15). Therefore, the driver will be alerted thanks to a vibration in the side of the seat corresponding to the side where the line has 13

15 been crossed, and will thus be able to retrieve a normal trajectory (See Figure II-16). It should also be highlighted that this system only works when activated by the driver and above a threshold speed value of 80km/h to avoid excessive alerts while driving in a city. Of course, one could wonder whether or not the driver should be able to desactivate this device. Indeed, anyone driving on a highway can see that very few people use their indicator when they change line. Therefore, anyone driving a car equipped with this technology will have the choice between putting the indicators each time he crosses a lane or switching off the system. Since any bad habit is quite difficult to change, most of driver who usually do not use their indicator would probably rather turn off the system. Thus this technology might only lead to significant results if imposed to the driver (noting that he can always buy an other car model), or coupled with a campaign aiming at making people more aware of the importance of the indicators on highways. e) Shoulder Rumble Strips (SRS) WS6,11 An alternative to the LDWS technology is to place shoulder rumble strips (See Figure II-17) on highways and other rural roads. According to an American study about the effectiveness of those strips, such devices were shown to reduce drive-off-the-road crashes by 30 to 50 percent or even more (figure 8, 9, 10). Figure II-17: Shoulder Rumble Strips (SRS) WS11 Figure II-17: Drift-off accident reductions in Pennsylvania WS11 Figure 9: Drift-off accident reductions [S5] Figure II-19: Drift-off accident reductions on Poarkway WS11 Figure II-17: Drift-off accident reductions in NewYork WS11 14

16 This kind of device has the huge advantage to apply to every single car when implemented on a road. Indeed, this does not only apply to brand new cars and the driver has no choice whether to use the system or not. If a driver begins to go off the road, he will automatically be alerted, with no possibility of any false alarm. Of course, the sound made by this device when driving on it might be a little annoying for the other passenger of the car, but this is a minor drawback as compared to the improvement of the safety. Yet, the installation of such strips depends strongly on the will of the different governments to invest in safety on roads and it might therefore take a lot of time before it can be implemented in every country, even if a study handled by the National Sleep Foundation WS6 in 1995 showed that this device have a positive benefit-to-cost ratio. L13, WS13 f) Lateral Position Tracking and Adaptive Cruise Control (ACC) As it has been said before, a drowsy driving implies an increased lane tracking variability. This parameter can easily be controlled by a radar system which use the two lane of the road to determinate an accurate lateral target positioning (See Figure II-18). This system can be combined with an Adaptive Cruise Control which can automatically reduce the speed and alert the driver if the car ahead is too close (See Figure II-19). The system proposed by Mobileye WS13, composed by both a camera and a radar, can also be used as a Lane Departure Warning (LDW) system and a pre-crash pedestrian protection system. Figure II-18: Lateral target positioning WS13 Figure II-19: Adaptive Cruise Control (ACC) WS13 An alternative to this technology for Lateral Position Tracking is to use the on board GPS. With this technology it is now quite simple to have access to the precise position of a vehicle and thus to calculate its lane tracking variation. Of course, as for the Steering Attention Monitor, these technologies are closely link to the environment of the car and might therefore be subject to many false alarms. Yet, combining these systems with a Steering Attention Monitor might lead to very good results since one technology can evaluate the behaviour of the car, while the other focuses on the driver. The data collected can therefore be compared in order to determine whether the driver is drowsy or not. 15

17 II.4) Recommendations The influence of drowsiness on the ability of a person to drive cannot be denied. As they are more likely to adopt a very dynamic way of life (with less sleep hours) and have less experience in driving, young people are the population risk at highest risk for an accident due to drowsiness. Most alarming is that a tired driver will tend to go faster in order to arrive sooner, therefore increasing even more the risk and the gravity of a crash. That is why, as shown before many technological solutions have been developed to detect drowsiness and thus try to avoid risky situation and accidents. Among all those systems, great hopes are put in the PERCLOS monitor. Indeed, this system should be able in a near future to evaluate very precisely the state of awareness of the driver, and therefore to warn him a long time before he falls asleep. Thus the driver should never be put in a dangerous situation because of drowsiness, as compared to some other technologies which wait to detect a dangerous situation to warn the driver (Nap zapper, lane departure warning system, shoulder rumble strips). Of course, all those technologies might reveal to be almost useless if there is no effort made concerning the education and formation of the driver. Every single people should try to be conscious of their own limits and seize the consequence of their acts as a driver. To go further, if the driver received a better formation, they should know how to avoid drowsiness. Some good advices to avoid drowsiness during a long driving trip are quoted below: Avoid driving during night Have a full sleep night of at least 7 hours before the trip Make breaks of at least 15 minutes every 2 hours Set correctly the ventilation or climate regulation Take caffeine drinks if needed Avoid having a heavy meal before starting out If all these advices were taken in account every day, for each driving trip, the risk of crashes due to drowsiness would decrease a lot. But often the drivers can t choose when and in which physical state they have to drive 16

18 III Alcohol and Driving III.1) Background a) Statistics WS13,14 Drunk driving is an important cause of traffic accidents causing deaths and injuries with a huge amount of monetary cost. In USA, the average percent of alcohol-related fatalities for the year 2003 has been estimated to 40% of all the fatal crashes, killing persons. In 2000, an estimated total of crashes in the USA involved alcohol, killing and injuring people. In Canada 48 % of public highway fatalities are caused by drivers who have been drinking beyond the legal limit set for driving. In 1999, more than Canadians were killed and were injured in alcohol related accidents. Drunk driving is not a new problem. First of all, it is a part of traffic safety, an issue gaining importance since the first cars were introduced and the first roads were constructed. b) Health Effects of Alcohol Use WS1 Ninety-five percent of all alcohol consumed is absorbed into the body through the stomach, small intestine and colon. Complete absorption into the blood requires 2-6 hours or more. The rate of absorption into the blood stream is influenced by the presence of food in the system, the time period of consumption, the driver s body weight and metabolism. Once alcohol is in the bloodstream, alcohol quickly goes to every cell and tissue in the body. Alcohol causes red blood cells to coagulate together in sticky wads, slowing circulation and depriving tissues of oxygen. Alcohol in the blood can cause anemia by reducing the production of red blood cells. Alcohol decreases the ability of white blood cells to destroy bacteria and degenerates the clotting ability of blood platelets. Alcohol kills brain cells, which is permanent damage. Long-term alcohol use causes loss of memory, impaired judgment, and learning ability due to the damage done to the brain cells. Alcohol affects the central nervous system of the body more than any other bodily function. Because alcohol is a depressant, it inhibits the control mechanisms of the brain, which results in unrestrained activities in various parts of the brain. An extremely high dose of alcohol can depress the central nervous system to a point where breathing may stop completely, resulting in death. Besides the effects alcohol has on the central nervous system, it causes damage and destruction to the tissue cells in the body including brain cells. Excess alcohol use can depress the appetite and prevent the absorption of amino acids, vitamins and other nutrients, which contribute to malnourishment of the body. Alcohol hampers the liver s ability to metabolize fat which leads to fatty liver disease and cirrhosis of the liver. Alcohol increases the blood pressure in people with hypertension, which can lead to life threatening heart problems. A large dose of alcohol can cause: blurred vision impairment in perception decreased mental alertness decreased physical coordination 17

19 An average of three or more servings per day of beer (12 oz.), whiskey (1 oz.), or wine (6 oz.) over time, may result in the following health hazards: Dependency Fatal liver disease Kidney disease Pancreatitis Ulcers Decreased sexual functions Increased cancers of the mouth, tongue, pharynx, esophagus, rectum, breast, and malignant melanoma Spontaneous abortion and neonatal mortality Birth defects Withdrawal from heavy alcohol use can lead to: Severe tremors Convulsions Death c) Effects of Alcohol in Your Blood WS2 Alcohol is a central nervous system depressant. How drinking affects your body and mind depends upon your blood alcohol concentration (BAC). BAC is related to how much alcohol you drink in a given period of time and your body weight. % of Blood Alcohol Concentration (BAC) Body Weight Number of Drinks in Two Hours* (lbs) BAC Effects 0.05% Relaxed state. Judgment is not as sharp. Release of tension; carefree feeling. 0.08%** Inhibitions are lessened. 0.10%** Movements and speech are clumsy. 0.20% Very drunk. Can be hard to understand. Emotions can be unstable. 100 times greater risk for traffic accident. 0.40% Deep sleep. Hard to wake up. Not able to make voluntary actions. 0.50% Can result in coma and/or death * 1 drink equals 11/2 ounces 80-proof hard liquor, 12 ounces beer, or 5 ounces wine. ** Some states use 0.08 as the lowest indicator of driving while intoxicated. Some use Table III-1: % of Blood Alcohol Concentration (BAC) and Effects WS2 18

20 III.2) Driving effects of alcohol use a) Crash risk L1 Through case-control studies, researchers have assessed the crash risks associated with different BACs. On average, the increased probability of crashing at increasing BACs is as follows: BAC Probability (relative to zero BAC).05 Twice.08 7 times times Table III-2: The increased probability of crashing at increasing BACs L1 b) Behaviour L1,2 According to the crash statistics in NSW, Australia, for the period , only 18% of all fatal crashes were alcohol-related. Table II-3 shows total number of fatalities and number of fatalities in alcohol-related crashes for the period Year N o of fatalities N o of fatalities in alcohol-related crashes Alcohol-related fatalities as % of total fatalities Average ( ) Table III-3: Total number of fatalities and number of fatalities in alcohol-related crashes, New South Wales, Australia L2 Compared to the other studies, these percentages seem to be underestimated. But an other result of this study is quite interesting: compared to other drivers involved in fatal crashes, drink drivers who are involved in fatal crashes are: three times as likely to have been speeding twice as likely to have not been using a protective device (seatbelt or helmet) seven times as likely to have been both speeding and not using a protective device 19

21 III.3) How to detect a drunk driver WS3 There are several indicators that a driver may be alcohol-impaired. Those indicators are listed here along with the percent possibility that the driver may be alcohol-impaired. 55% to 65% Turning with a wide radius Straddling center line or lane marker Appearing to be impaired (leaning forward, clutching steering wheel, oblivious to outside events, et. al.) Almost striking an object or vehicle Weaving Driving on other than designated roadway Swerving 40% to 50% Driving at a speed which is ten to twenty miles per hour slower than the posted limit Stopping without cause in traffic lane Following too closely Drifting Tires on center lane or lane marker Braking erratically Driving into opposing or crossing traffic Slow response to traffic signals Signaling inconsistent with driving actions 30% to 35% Stopping inappropriately Turning abruptly or illegally Accelerating or decelerating rapidly Headlights off at night III.4) Technological solutions a) Enforcement Devices WS4 There are three major types of breath alcohol testing devices. Regardless of the type, each device has a mouthpiece, a tube through which the suspect blows air, and a sample chamber where the air goes. The rest of the device varies with the type. - Breathalyzer Breathalyzer is a device to measure the amount of alcohol in blood. Alcohol that a person drinks shows up in the breath because it gets absorbed from the mouth, throat, stomach and intestines into the bloodstream. Because the alcohol concentration in the breath is related to that in the blood, you can figure the BAC by measuring alcohol on the breath. The ratio of breath alcohol to blood alcohol 20

22 is 2,100:1. This means that 2,100 milliliters (ml) of alveolar air will contain the same amount of alcohol as 1 ml of blood. Figure III-1: BreathalyzerWS4 Figure III-2: Breathalyzer UsageWS12 - Intoxilyzer Intoxilyzer can detect alcohol by infrared (IR) spectroscopy, which identifies molecules based on the way they absorb IR light. Molecules are constantly vibrating, and these vibrations change when the molecules absorb IR light. The changes in vibration include the bending and stretching of various bonds. Each type of bond within a molecule absorbs IR at different wavelengths. So, to identify ethanol in a sample, you have to look at the wavelengths of the bonds in ethanol and measure the absorption of IR light. The absorbed wavelengths help to identify the substance as ethanol, and the amount of IR absorption tells you how much ethanol is there. Figure III-3: Intoxilyzer 5000CWS8 Figure III-4: Intoxilyzer 300WS9 - Alcosensor III or IV Alcosensor can detect a chemical reaction of alcohol in a fuel cell. The fuel cell has two platinum electrodes with a porous acid-electrolyte material sandwiched between them. As the exhaled air from the suspect flows past one side of the fuel cell, the platinum oxidizes any alcohol in the air to produce acetic acid, protons and electrons. The electrons flow through a wire from the platinum electrode. The wire is connected to an electrical-current meter and to the platinum electrode on the other side. The protons move through the lower portion of the fuel cell and combine with oxygen and the electrons on the other side to form water. The more alcohol that becomes oxidized, the 21

23 greater the electrical current. A microprocessor measures the electrical current and calculates the BAC. Figure III-5: Alcosensor WS10 b) Non-enforcement device WS5,6,7,11 - Alcohol Interlock An alcohol interlock device is an electronic breath-testing device connected to the ignition of a vehicle. The vehicle will not start unless the driver passes a breath test. It is a small breath-testing device, about the size of an electric shaver, which can be fitted to your vehicle. It measures your breath alcohol level when you blow into it, allowing you to drive legally, but preventing you from driving after drinking. Figure III-6: Alcohol Interlock WS11 Figure III-7: Alcohol Interlock Usage WS7 III.5) Recommendations The technological solutions for the drunk driving need cooperation of drivers. But it is difficult that drivers would detect themselves before driving. Then, effective solutions would be to use laws and enforcement controlling drivers not to drive when they are drunk. Another way to solve this problem is to educate drivers how drunk driving affects to road accidents. 22

24 IV Drugs and Driving IV.1) Background Drugs (mainly marijuana and cocaine) are involved in about 18% of motor vehicle driver deaths in the United States. These drugs are generally used in combination with alcohol involving a particular level of impairment. (NHTSA 2003). Drugs whether prescription, over-the-counter or illegal drugs can impair necessary driving skills including vision, reaction time, judgment, hearing, and simultaneous task processing/accomplishment. Driving requires other cognitive skills, such as information processing and psychomotor skills, which may also be impaired by the use of drugs. IV.2) Effects of the illegal drugs WS1,2,3,4 - Marijuana After alcohol, delta-9-tetrahydrocannabinol (THC), marijuana's major psychoactive constituent, is the drug which is found most often in the blood of drivers involved in road accidents. THC has a very different effect from alcohol. Pot users are acutely aware of their impairment - that is, they feel "high" - and some try to compensate by driving more cautiously. THC diminishes psychomotor skills and attention span. It reduces the ability to perform tracking tasks; at high doses, users drive less accurately and show difficulty with steering. Alcohol additionally impairs cognitive function, including risk perception, decision-making and planning. It can also trigger aggressive driving behaviour such as speeding and following too closely. - Cocaine Cocaine is a strong central nervous system stimulant that interferes with the reabsorption process of dopamine, a chemical messenger associated with pleasure and movement. Dopamine is released as part of the brain's reward system and is involved in the high that characterizes cocaine consumption. Physical effects of cocaine use include constricted peripheral blood vessels, dilated pupils, and increased temperature, heart rate, and blood pressure. The immediate euphoric effects of cocaine include hyper-stimulation, reduced fatigue, and mental clarity. Some Immediate side-effects are: Fast heartbeat and breathing and increases in blood pressure and body temperature Erratic or violent behavior Blurred vision, chest pain, nausea, fever, muscle spasms, convulsions Drivers under the influence of cocaine have an impaired coordination and vision. They maintain the illusion of being alerted and stimulated, guided by confusion and the tendency towards impulsive behaviour. 23

25 - Opiates Opiates are used to relieve severe pain. They are medically used as strong painkillers and surgical anaesthetics. Opiates affect many organs through the autonomic nervous system, which controls such body functions as circulation, respiration, and digestion. They cause blood vessels to relax and heartbeat to slow, lowering blood pressure. They slow and weaken contraction of muscles that control breathing and constrict intestinal muscles, slowing digestion. As do most drugs of abuse, opiates induce euphoria, in this case a sense of contentment and physical relaxation. Drivers under the influence of opiates experience drowsiness, grogginess and mental confusion due to the sedative effect of opiates, so opiates lead to mental and physical impairment. - Amphetamines Amphetamines speed up the nervous system and act as mood enhancers. Amphetamines often make the user feel good, happy and relaxed at least at first. Contrary to rumors, they are not an aphrodisiac and can actually inhibit sexual performance. Some common side effects can be quoted: increased heart rate, increased body temperature, anxiety, increased blood pressure, increased confidence, nausea, feelings of well-being, sweating, loss of appetite. Drivers under the influence of amphetamines have impaired concentration and vision and tend to overestimate their own capabilities. - Hallucinogens (LSD and PCP) The term hallucinogen is used to describe naturally occurring or synthetic drugs taken primarily for the distorting effects they have on the user s perceptions. Hallucinogens effects range from mild sensory distortion to hallucinations, paranoia, and delirium. This means drivers under the influence of hallucinogens have distorted impressions of time, space and distance and, thus, are heavily mentally and physically impaired. - Tranquilizers Tranquilizers have a calming and sedative effect. The use of tranquilizers produces drowsiness, a lack of coordination, altered perceptions, memory impairment, poor control of speech, and slower reaction time. Effects on driving include poor tracking, difficulty in maintaining lane position, and neglecting roadside instructions. 24

26 L1, WS1 IV.3) Laws in different countries - Europe In general, all European countries have specific regulation on driving under the influence of drugs and/or medicines. Banned drugs common in most of the countries are: Amphetamines, Cannabinoids, Cocaine, MDMA, MDEA and MBDB, Heroin and morphine. In general, there are no specific rules for particular categories of drivers. A good indicator for the growing importance that is being paid to this topic is the number of recent changes in legislation, in the EU 15. These are as follows: In 2003, blood test in Austria is compulsory if a driver is suspected to be influenced by drugs In 2002, drug driving offences became very serious in Spain In 2003, drugs were included in the French road code In 2003, more severe sanctions and modified modalities for checks were included in the Italian rode code. In some countries the sanction regime for drugs and medicines is identical to the drink and driving sanction regime (for instance, in Germany). However, in most of the countries, drug driving falls only or mainly under the criminal law. Lowest defined values for financial penalties, in the national ranges, are in force in Belgium (100 ), Netherlands (190 ), Greece (150 ), Italy (258 ) and Netherlands (190 only for first time offenders). Highest values for financial penalties in the national ranges are in force in Belgium ( ), France (cumulative use of drugs and alcohol while driving and use of drugs while driving ), Austria and Ireland (around 3650 ). Regarding restriction of liberty (imprisonment), sanctions in force are as follows: Up to 2 years: Italy, (up to 30 days), Belgium (15 to 180 days), United Kingdom (up to 180 days), Portugal (from 120 to 365 days), France, Sweden, Finland (up to 2 years) and Denmark (up to 1 year) Up to 5 years: Germany In Spain, house arrest sentences can be applied if no aggravating circumstances have occurred At least 2 months: Greece Suspension of driving licence, disqualification from driving, points added to the individual register of the driver (penalty points schemes) and alternative sanctions can also be applied (sole or cumulatively). - Canada: The police usually rely on symptoms of impairment, driving behaviour and witness testimony when enforcing drug-impaired driving offences. However, they can only ask a driver to participate voluntarily in tests for drug impairment. The police have not the authority to demand physical tests and body fluid samples from suspected drug-impaired drivers. 25

27 IV.4) Technological solutions WS4,5,6 Drugs can be detected very reliable and exact by special laboratories. This can take hours, up to days until the results are available. Here blood, urine and hairs are used. Of course, those test methods are not suitable in order to detect an impaired driver before or during driving. The role model for a device detecting a driver under the influence of impairing drugs is an equivalent to the breathalyser devices, that are used to detect drunk drivers. Such a system has to fulfil a lot of requirements. It has to be fast, reliable, sensitive, exact and repeatedly applicable and can not be bypassed. Therefore the police and emergency physicians use quick saliva tests with test strips, that show if and which drugs have been taken. But the reliability and sensitivity of those saliva tests is very low. There is a lot of research work being done to develop improved test devices, for example using socalled bio-chips. The main focus for evaluating those devices is the sensitivity for detecting d9- THC (Marijuana). This psychoactive constituent of Marijuana can be detected very badly, because it is almost water-insoluble. Apart from the very high sensitivity this bio-chip system promises additional advantages such as up to 100 simultaneously detectable substances. Some advantages of saliva analysis for drugs of abuse are quoted below: Ease of collection: The collection of oral fluid is a noninvasive means of collecting a suitable specimen for analysis for drugs of abuse. In a matter of minutes, the sample is produced. Real time values: The oral fluid sample provides a good indication of recent drug use. Most drugs are present in the saliva for 2-4 days after use. This corresponds to the approximate times that the drugs are detected in the urine except for THC and PCP. Because THC and PCP are fat soluble, these drugs remain in the body longer and can be detected in the urine sometimes for weeks after usage. Thus, only recent use of THC and PCP can be detected in the oral fluid. Drugs detected at low concentrations: Since the levels of drugs are much lower in the oral fluid (saliva), different methodologies of testing are necessary to detect the drugs. The police use the screening method ELISA (enzyme-linked immunosorbent assay) and the confirmation of positives is done by GC/MS (gas chromatography mass spectrometry). IV.5) Recommendations The generalised difficulty in the control of any rules regarding abused drug use has to do with the nature of the tests needed to detect drugs or medication. Because the use of screening devices has not yet become common in drug enforcement, roadside tests are limited to the visual assessment by the police. Therefore, training of police officers assumes particular importance. So one way to overcome those problems would be an impairing drugs detecting device implemented in the car and connected to an interlock ignition system. Such a system, comparable to the breathalyzers used for alcohol detection, would be very expensive, if you think of the circumstances, that a part being implemented in a production car may not cost more than 10 to 15. And this is the highest category. 26

28 V Elderly drivers V.1) Background a) Introduction The purpose of this part is to present you what is the effect of age on driving. As everyone ages differently, some people are perfectly capable of driving in their seventies, eighties or even beyond. However, a loss of motor functions (visual, hearing acuity, ) chronic diseases and physical impairments and use of medications generally go hand in hand with age. Those impairments factors are studied for elderly persons, more susceptible to develop them but it can be widely generalized to anybody developing diseases presented below. Given that in most cases no technical solutions have been developed specifically for elderly drivers, recommendations through this report are given to help them deal with diseases in relation with driving. But first let s study if elderly drivers are, as some puts it, a threat on roads. b) Collisions rates per licensed drivers involving elderly persons WS1,2,3 Driving safely requires the integration of complex motor, visual and cognitive tasks. Although those abilities tend to decrease with age, elderly drivers can continue to drive safely, mainly owing to the fact that they develop an instinctive pattern of driving. In order to compensate for moderate functional deficits, most elderly persons avoid indeed rush hours and drive fewer kilometres with shorter distances and less at night. Moreover, elderly drives are more cautious than younger drivers, take fewer risks in traffic and drive more slowly. Considering this way of driving, they have fewer collisions. This statement is by the way shown on the graph below, which represents the collision rate per 1000 licensed drivers according to the age. It is clearly stressed that collision rates decrease steadily with age, putting as a myth criticisms blaming that elderly drivers are responsible for a disproportionate number of car accidents. Figure IV-1: Motor vehicle collision rates per 1000 licensed drivers according to age WS2 To conclude, relatively few deaths of elderly persons (1 percent) involve motor vehicles. Cancer, heart disease and health issues are indeed the leading causes of death among people 65 years old and old. 27

29 c) Traffic collisions per kilometres driven WS1,2,3 Per kilometres driven, elderly drivers have however higher risks of traffic violations, collisions and rates of fatal crashes than all age groups over age 25. As it can be seen on the following graph, fatal collisions rates per miles driven increase after about age 60 and rise sharply after age 75. It turns out that elderly drivers do not deal as well as younger drivers with driving tasks that require complex decision making. Failing to yield, turning improperly and running stop signs and red lights are common violations. Elderly drivers have also a higher proportion of collisions at intersections, involving most of the time more than one vehicle. Furthermore, an elderly person (65 and older) who is involved in a car accidents is more susceptible to be seriously injured, more likely to require hospitalization and more likely to die than younger people involved in the same crash. Figure IV-2 : Fatal crash involvement per 100 million miles according to age WS3 Elderly persons have higher risks to develop medical diseases or functional deficits which can limit their ability to drive. The following paragraphs list some of them and their influence on the driving skills. V.2) Effects of age on the driving abilities L2, WS1 a) Motor functions The muscle strength (particularly the grip strength decreases) decreasing with age makes driving more difficult. We will see in the visual function paragraph that the field of view decreases with eye modifications due to age. But a limited mobility of the neck can produces the same result. Limited mobility of the shoulder, wrist, elbow or hand can also affect steering. The reaction time can be divided into 2 parts: movement time and choice time. The reaction time increases with the difficulty and the number of choices, but also with the time needed to perform the decision. Elderly people have slower movements than younger people, which in some cases can be very dangerous in urgency situation. 28

30 Today non power assisted or power assisted devices are able to help people with limited mobility. For example, spinner knobs (See Figure IV-3) can be installed on the steering wheel. This device is not expensive (around 20 ) and make driving easier for drivers with limited arm or shoulder mobility. Radars and video camera can be used to replace rear and side mirrors and compensate the limited field of view as it does for usual drivers. Figure IV-3: Spinner knobs WS5 L1, WS1,6 b) Visual functions Vision is a very important sense used by man to organize movement which is of course essential when driving. Several studies have shown and everyone can notice that the visual function efficiency decreases with age. But we need to know exactly what is going on with eyes in order to find suitable solutions for elderly drivers. Some studies state that with age there are changes in the optics of the eye. The first modification is what is called light absorption phenomenon. The cornea becomes thicker and loses its transparency; metabolic changes and a defect of hydration of the crystalline lens cause its yellowing. The yellowing of the eyes optic produces changes in colour perception. For example, older people have more difficulties to see a purple object on a red background (See Figure IV-4). Age 20 Age 60 Age 75 Figure IV-4: Color perception vs. age WS6 Furthermore, the pupil shrinks and the pupillary reflexes are weak and slow. That is why the light adaptation, which is the time for the eye adjusts from light to dark or to dark to light (From example when we drive into a tunnel) becomes higher with the age. It means that older drivers can almost be blind when they drive from a light to a dark place (and vice versa) increasing the accident risk. Changes in eye movements can also explain why older people have difficulties to judge very slow or very fast motions and to well estimate distances. The capacity to detect peripheral signals is degraded with age, the size of the driver s field of view decreases significantly. The restriction in the useful field of view predisposes elderly drivers to ignore road information. When the eye is adapted to a specific brightness, sources much more intense than the current level produce glare. Due to the clouding of the eye's optics of older people, the quantity of light diffused or reflected by the various parts of the eye is more significant for old people, which leads to reduce 29