Abstract:
A light tracking apparatus mounted on a movable vehicle includes a power source for the light tracking apparatus. There is at least one light receiving means for detecting reflected light from the surface marking and surrounding background. A computing means is included for processing the difference between intense and weak reflected light from the pavement marking providing a signal indicating a significant change in light intensity, and an alarm means responding to said signal for indicating a that change in the light intensity.  
     A method of operating a light tracking apparatus mounted on a movable vehicle includes engaging a power source for the light tracking apparatus. The next step includes providing at least one light receiving means for detecting reflected light from the surface marking and surrounding background. A computing means is used for processing the difference between intense and weak reflected light from the pavement marking providing a signal indicating a significant change in light intensity. The final step is engaging an alarm means responding to said signal for indicating that change in the light intensity.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a vehicle safety device and, more particularly, to a device that tracks the position of a moving vehicle relative to its location along a road.  
         BACKGROUND OF THE INVENTION  
         [0002]    Modern highway systems have allowed passengers in vehicles to safely travel great distances. Nevertheless, a large number of vehicular accidents occur that cause significant loss of life and property. The overwhelming majority of automobile collisions are caused by driver inattention, exhaustion and falling to sleep at the wheel of a vehicle. The conditions that lead to the driver&#39;s loss of concentration allow the automobile to deviate off-course and collide with surrounding objects. The early signs of fatigue include staring blankly at the road and a reduction in the rate of eye blinking. The drivers of motor vehicles, particularly on long highway drives, are frequently stricken by fatigue and need to stop and rest in order to return to an alert condition. Frequently the driver is many miles from the nearest available and safe roadside rest stop.  
           [0003]    There are some prior art devices and methods that have been used in an attempt to increase vehicular safety on the highway. Such devices include devices to sense indications of when the driver is becoming fatigued such as nodding of the head or erratic steering wheel movements. For example, one such invention uses glasses as part of a system to detect the sleeping driver and to provide an awakening alarm. The system attempts to use the closing of the eyes to activate an alarm signal. A timer provides a delay period between the closing of the eye and the activation of the alarm. Devices that depend on indications of sleep have been found to trigger an alarm that may be too late to be of use in preventing accidents.  
           [0004]    In another invention described in U.S. Pat. No. 5,717,399, an obstacle detection system for vehicle use is described which utilizes a plurality of electromagnetic antennas for transmitting FM radio waves. The electromagnetic antenna has poor detection of nearby objects because of its narrow directivity. As a result, a plurality of electromagnetic antennas are necessary, within a single radar module, to provide a wide detection angle for the nearby object. The obstacle detection system receives reflected radio waves for detection of nearby objects as well as remote objects in order to cover a wide detection range. However, this involves additional and complex circuit configurations and mechanical structures with an attendant cost increase for manufacture of the system. Furthermore, when the plurality of the differently oriented electromagnetic antennas are combined into one radar module the individual antennas have to be activated sequentially to monitor individual areas one by one in the detection zone. Consequently, there is a problem with this detection method because the nearby object is detected last in the sequence. This causes a time delay in the detection response wherein the driver of the vehicle has already veered of the road.  
           [0005]    Another obstacle detecting device projects light, ultrasonic waves or electromagnetic waves in a specified forward or backward direction to and receives reflected waves from an object or obstacle. This system is an optical distance apparatus utilizing image sensors that include a pair of first and second optics with two convex lenses disposed in a horizontally aligned relation at a prescribed distance away from each other. It is possible to detect the presence or absence of an object lying in the direction in which the ultrasonic or electromagnetic waves or light are projected. However, it is difficult to determine whether the object detected is an obstacle to the travel of the vehicle. For example, when a vehicle is travelling on a curved road, the obstacle detecting apparatus can misidentify a guide rail as an obstacle. In addition, many transmitters and receivers are required in order to determine the location and direction of an object with respect to the moving vehicle. This results in a great increase in size and costs of manufacturing the overall apparatus.  
           [0006]    In U.S. Pat. No. 5,929,784 an invention is disclosed for determining the distance to a road lane white line marking from a travelling vehicle. This is accomplished by two imaging lenses and two light receivers each with three light sensor arrays that detect a continuous straight white line that connects only a point of maximum value in a distribution of quantity of light on each sensor array. The line image is detected only when the sensor arrays are maintained within a predetermined narrow range for a predetermined length of time. The sensors are arranged parallel to a plane perpendicular to the optical axis of the lens thus perpetuating the narrow range of the system. For example, if a white line in the road is not a solid line, such as a dotted center line or a curved white-line, the system fails to operate. The white-line detector calculates the difference in data value between two successive pixels in each sensor along its longitudinal line. This difference in value is compared to a previous value with the final outcome being a signal output. When there is a constant change from white-line to road and back again the system detects each successive dotted white line as a first time detection and recalculates the difference in data value between two successive pixels. Consequently, there can be a constant error in the final output signal. Additionally, when the white-line is curved the system is inoperative because the sensor arrays are not angled or positioned in the narrow range required for the system to operate.  
           [0007]    What is needed is an inexpensive system that will alert drivers of any type of vehicle that the vehicle is moving outside the lane markings on any road or highway. What is further needed is a system that operates with changing road conditions.  
         SUMMARY OF THE INVENTION  
         [0008]    It is an aspect of the present invention to use existing highway or road surface markings to detect the position of a moving vehicle relative to those surface markings.  
           [0009]    It is yet another aspect of the present invention to provide a light tracking apparatus for moving vehicles.  
           [0010]    It is still another aspect of the present invention to provide a light tracking apparatus for vehicles that is both inexpensive to manufacture and simple to operate.  
           [0011]    To accomplish these and other aspects a light tracking apparatus mounted on a movable vehicle includes a power source for the light tracking apparatus. There is at least one light receiving means for detecting reflected light from the surface marking and surrounding background. A computing means is included for processing the difference between intense and weak reflected light from the pavement marking providing a signal indicating a significant change in light intensity, and an alarm means responding to said signal for indicating a that change in the light intensity.  
           [0012]    A method of operating a light tracking apparatus mounted on a movable vehicle includes engaging a power source for the light tracking apparatus. The next step includes providing at least one light receiving means for detecting reflected light from the surface marking and surrounding background. A computing means is used for processing the difference between intense and weak reflected light from the pavement marking providing a signal indicating a significant change in light intensity. The final step is engaging an alarm means responding to said signal for indicating that change in the light intensity.  
           [0013]    These and other aspects of the claimed invention will become apparent from the following description, the description being used to illustrate a preferred embodiment of the claimed invention when read in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 shows a block diagram of the whole configuration of the preferred embodiment of the invention.  
         [0015]    [0015]FIG. 2 is the logic diagram used to provide microprocessor software to operate the preferred embodiment of the invention.  
         [0016]    [0016]FIG. 3 shows the preferred embodiment of the invention positioned in a vehicle on a highway.  
         [0017]    [0017]FIG. 4 shows the operation of the light detector portion of the preferred embodiment of the invention.  
         [0018]    [0018]FIG. 5 is a detailed portion of the scanning area of the light sensor in the preferred embodiment of the invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    While the claimed invention described below references tracking moving vehicles, a practitioner in the art will recognize the principle of the claimed invention are applicable elsewhere, for example, mobile equipment and the like.  
         [0020]    As can be seen in FIG. 3 one feature of highways is the pavement markings  51   a ,  52  and  51   b  that separate a first lane  50   b  from the second lane  50   c  and from the shoulder  50   d  of the highway  50   a . A vehicle  53  travelling properly within a lane in a highway  50   a  maintains a given distance from these pavement marks. As long as the vehicle  53  is properly driven, the first distance  54  from the first pavement marking  51   a  and the second distance  57  from the second pavement marking  52  is constant within a tolerance interval. There are only limited situations in which a vehicle&#39;s distance from any pavement markings would vary substantially. For example, a vehicle makes a planned lane change, a vehicle is exiting a highway, a vehicle stops at the shoulder of the highway, a vehicle is inattentively driven or the pavement marks are absent. A vehicle  53  is typically a passenger automobile, a truck, a bus, mobile equipment or a recreation vehicle.  
         [0021]    The pavement markings as shown in FIG. 4, being either yellow or white in color or are reflectors that reflect a greater amount if incident light compared to the surround asphalt or concrete. The first surface area  17   a , in FIG. 5, comprises a left side background  17   b  of the first pavement marking  51   a  and a right side background  17   c  of the first pavement marking  51   a . The intensity of light reflected from the first pavement marking  51   a  is greater that the gray background of the left side  17   b  and the right side  17   c . A first light sensor  18   a  is mounted on vehicle  53  and positioned to provide a first sensor measurement  54   a  of the first surface  17   a . The first light sensor  18   a  measures reflected light from the first surface area  17   a  and either detects the presence of the first pavement marking  51   a  or does not detect the presence of the first pavement marking  51   a , depending on the position of vehicle  53  on the highway  50   a . As is shown in FIG. 3 and FIG. 4 a second light sensor  18   b  is also positioned on vehicle  53  to provide a second sensor measurement  57   a  of an area around the second pavement marking  52 . As is understood by the practitioner in the art, the light tracking apparatus  10  functions with one, two, three, four or more light sensors, depending on the application, to measure the reflected light intensity of the pavement surface markings. Furthermore, a first light source  19   a  directs light to a first pavement marking  51   a  and a second light source  19   b  directs light to a second pavement marking  52  when needed for the first and second light sensors to detect reflected light. The light sources are typically required during night driving of the vehicle. Alternately, in conjunction with the same number of light sensors, the light tracking apparatus  10  functions with one, two, three, four or more light sources.  
         [0022]    Now referring to FIG. 1, it shows the whole configuration of the light tracking apparatus  10 . A controller  10   a  includes a microprocessor and its peripheral devices. The microprocessor includes a MPU  11  (microprocessor unit), a RAM  13  (random access memory), a ROM  14  (read only memory), an input port  12 , an output port  15  and a common bus  11   a . A first light source  19   a  and a second light source  19   b  provide a regulated amount of light beamed directly at the pavement markings and surrounding background of a road, highway or the like. A first light sensor  18   a  and a second light sensor  18   b  each provide a signal to the controller  10   a , by measuring reflected light from pavement markings on a road, highway or the like where the light source was directed to. A power source transformer  20  provides DC voltage to apparatus  10 . A switch  22  is provided to turn the system on and off. A day/night sensor  21  determines if there is enough background light for apparatus  10  to operate and provides a control signal to operate the first light source  19   a  and the second light source  19   b . Finally, an alarm  16  is provided that activates when not enough reflected light is measured by the first light sensor  18   a  and the second light sensor  18   b . In other words when vehicle  53  in FIG. 3 veers off of highway  50   a  then the light tracking apparatus  10  activates alarm  16  to alert the driver.  
         [0023]    The power source  23  for energizing the components of the light tracking apparatus is typically obtained from the 12 volt DC battery of an automobile or other type of vehicle. In other applications the DC voltage is substitutable for AC power obtained from 110 volt AC outlet. In yet another application DC voltage is obtainable from photovoltaic cells mounted on a vehicle. In any application a power source transformer  20  is provided to allow apparatus  10  to operate as a low voltage system. Low voltage electrical energy is provided at a MPU  11  through a first circuit  20   a , an alarm  16  through a second circuit  20   b, a  day/night sensor  21   a  through a sixth circuit  20   f, a  first light source  19   a  through a fourth circuit  20   d  and a second light sources  19   b  through a fifth circuit  20   e . Furthermore, low voltage electrical energy is provided at a first light sensor  18   a  and a second light sensor  18   b  through a third circuit  20   c  and a seventh circuit  20   g , respectively. Typically, the power transformer  20  is a single transformer but the single transformer is substitutable for a number of transformers individually providing low voltage power to the different components of apparatus  10 .  
         [0024]    The switching means  22  consists of a manual on-off toggle device to engage (activate) or disengage (deactivate) the light tracking apparatus  10 . In the preferred embodiment of the invention the switching means  22  further consists of a vehicle&#39;s turn-signal indicator switch device. When a driver is making a conscious lane change, the alarm  16  is temporarily deactivated so that it will not result in sounding the alarm  16 . Alternately, a photo sensitive switch device (not shown) is incorporated into the light tracking apparatus  10  so as not to allow it to operate during day light hours. As is known by the practitioner in the art, the switching means  22  is a variety of devices that engage/disengage power to apparatus  10 .  
         [0025]    A light emitting means consists of a first light source  19   a  and a second light source  19   b . Alternately the light emitting means consists of one, two, three, four or more light sources to provide an adequate amount of light for apparatus  10  to operate. For example, the light emitting means might consist of two sets of three light sources on each side of a vehicle. If one light source were to malfunction then the other light sources would be adequate for continued operation of the apparatus  10 . The light emitting means of the preferred embodiment of the invention projects light onto a pavement marking and surrounding background. Typically the light emitting means is activated only during the night when it is dark. It provides light so that the light sensors measure intense reflected light from the pavement marking and weak reflected light from the surrounding background.  
         [0026]    It is a feature of the light sources that they are typically a wide variety of light sources such as incandescent bulb, light emitting diode and infra-red. For example, the first light source  19   a  and second light source  19   b  can produce light in either the visible or infrared portion of the light spectrum. Regardless of the particular light source used, the light source is typically powered from a DC power source that is low voltage such as 12 volts. The light source is operated at times of low light conditions so that the proper amount of light is reflected from the first surface  17   a  and the second surface  17   b , respectively, to the first light sensor  18   a  and the second light sensor  18   b.    
         [0027]    Regardless of the number or type of light sources used, each light source is separately mounted on one side of vehicle  53  and the opposite side of vehicle  53 . Preferably, the light sources are mounted and aligned so that the incident angle of light will reflect back to the light sensors from the pavement markings in the first surface  17   a  and the second surface  17   b . That is to say that the light emitted from the first light source  19   a  provides a beam of light with a first angle of incidence  61  and the light emitted from the second light source  19   a  provides a beam of light with a second angle of incidence  59 . The first light sources  19   a  with the first angle of incidence  61  and the second light source  19   b  with the second angle of incidence  59 , as shown in FIG. 3, is directed respectively to the first pavement marking  51   a  and the second pavement marking  52 . These angles of incidence are such that the reflected light from the first and second pavement marking, respectively, are measured by the first light sensor  18   a  and the second light sensor  18   b . It is very important to achieve the correct first angle of incidence  61  and the second angle of incidence because of vehicle headlights from other vehicles on highway  50   a . One reason for this is because approaching vehicle headlights create a spot in the highway surface diffusing reflection from the surface markings causing erroneous measurement of the first light sensor  18   a  and/or the second light sensor  18   b.    
         [0028]    A light receiving means for detecting gradations of intensities of incident reflected light from the pavement marking and surrounding background includes a first light sensor  18   a  and a second light sensor  18   b . Alternately the light receiving means consists of one, two, three, four or more light sensors to detect an adequate amount of reflected light for apparatus  10  to operate. Typically the light receiving means is an infra-red sensor, an optical sensor, silicon photodetectors or retroflective sensors. The first light sensor  18   a  receives reflected light from a first surface area  17   a  while the second light sensor  18   b  receives reflected light from a second surface area  17   b . As long as the first sensor  18   a  and the second sensor  18   b  continue to measure uniform reflected light, the relative distances, that is the first distance  54  and the second distance  57  and/or the incidence of light upon the sensors, is the same. If the first sensor  18   a  and/or the second sensor  18   b  suddenly measures (detects) reflected light intensity substantially lower than previously measured (detected), then the position of the sensors relative to the pavement markings must have changed. In such an instance, the assumption would be that vehicle  53  has veered out of its first lane  50   b  into either the second lane  50   c  or the shoulder  50   d  of highway  50   a.    
         [0029]    In one embodiment of the invention, in a situation where a driver is operating the vehicle  53  along a solid first pavement marking  51   a , single sensor the first light sensor  18   a  mounted on the vehicle  53  will suffice. The first light sensor  18   a  will be positioned on vehicle  53  such that the sensing angle would correspond to the position of the first pavement marking  51   a . However, in more complicated driving conditions, when pavement markings are less predictable and when precise positioning of the vehicle  53  is desired, apparatus  10  includes a first light sensor  18   a  and a second light sensor  18   b . Typically, the first light sensor  18   a  is located on one side of the vehicle  53  and the second light sensor  18   b  is located on the opposite side of the vehicle  53 . The first light sensor  18   a  measures reflected light from the first pavement marking  51   a  while the second light sensor  18   b  measures reflected light from the second pavement marking  52 . Furthermore, if for example, the second pavement marking  52  is a broken line separating the first lane  50   b  from the second lane  50   c  of highway  50   a , the second sensor  18   b  will still properly measure the position of vehicle  53  within the first lane  50   b . This is accomplished by measuring reflected light and providing a signal to the MPU  11  that is programmed to report an average intensity of light. Alternately, the second light sensor  18   b  and a third light sensor (not shown) are positioned on same side of vehicle  53 . They face the broken second pavement marking  52  but are angled differently such that the second light sensor  18   b  is measuring the broken second pavement marking  52  and the third light sensor (not shown) is detecting in between the broken second pavement marking  52 . Thus one sensor is always reporting an intensity of light.  
         [0030]    The light receiving means first light sensor  18   a  and second light sensor  18   b  are operated on 12 volts, direct current, having a range between 2 feet and 10 feet, a beam spread of 20° or so and an angle of tilt of plus or minus 10° or so. It functions like a simple rheostat switch by moving between a normally open position when no reflection of light is detected and a closed position when the reflection of light is detected. The fully open position prevents the passage of electrical energy therethrough while the fully closed position allows the passage of electrical energy therethrough. In between are various values of electrical energy that provide the MPU  11  with a signal for the apparatus  10  to operate.  
         [0031]    The light receiving means first light sensor  18   a  and second light sensor  18   b  has two or more distinct range sensitivity that is automatically selected by controller  10   a  to thereby vary the reach of the sensors. The sensors have a short range sensitivity selection to detect the first surface area  17   a  and/or second surface area  17   b  that is between 2 feet and 4 feet. Alternately, the sensors have a long range sensitivity selection to detect the first surface area  17   a  and/or the second surface area  17   b  that is between 4 feet and 10 feet.  
         [0032]    The light receiving means further includes a day/night detection circuitry  21 . The day/night detection circuitry  21  includes a day/night light sensor  21   a  for detecting whether or not there is adequate amount of background light for apparatus  10  to operate without a light emitting means. In other words, does the day light provide enough light so the light receiving means detects the reflected light from the first payment marking  51   a  and the second payment marking  52 . The day/night light sensor  21   a  provides a signal to the MPU  11  to either activate or deactivate the light emitting means. The day/night detection circuitry further controls and varies the intensity of light emitted from the light emitting source in conditions that do not either fully activate or deactivate the light emitting source, that is like cloudy day light hours.  
         [0033]    An alarm means that is an alarm  16  indicates a change in the position of vehicle  53  that is veering off highway  50   a . The alarm  16  receives a signal from the controller  10   a  that the first light sensor  18   a  and/or the second light sensor  18   b  is no longer measuring enough reflected light from either the first pavement marking  51   a  and/or the second pavement marking  52 . Typically the alarm  16  is an electronic alarm beeping out pulsating sound waves. These sound waves are strong enough for the driver of vehicle  53  to notice hear the sound waves and notice the vehicle  53  is veering off the highway  50   a . Alternately, the electronic alarm  16  is substitutable for a siren, horn or flashing light The computing means includes controller  10   a  with a MPU  11 , a RAM  13 , a ROM  14  and common bus  11   a . The computing means further includes a software structure  100 , as shown in FIG. 2, of the controller  10   a  The computing means processes the difference between intense (strong) and not so intense (weak) reflected light received from the pavement markings and surrounding background. A signal is provided to alarm  16  indicating a significant change in the light intensity, that in other words shows the driver of vehicle  53  is veering of the highway  50   a.    
         [0034]    In FIG. 2, software structure  100  provides the necessary logic for programming apparatus  10  to operate. The software structure  100  at a first decision  101  determines whether there is enough natural light to operate. If the first path  101   a  is chosen then the first step  102  deactivates or reduces the amount of light being emitted from the first light source  19   a  and the second light source  19   b . If the second path  101   b  is chosen then the second step  103  activates and/or increases the amount of light emitted from the first light source  19   a  and the second light source  19   b . When the first step  102  reduces the amount of emitted light from the light sources a third path  102   a  is chosen and a second decision  106  determines whether there is enough reflected light from the first pavement marking  51   a  and the second pavement marking  52 . When the second step  103  activates or increases the amount of light emitted from the light source, it follows that in the third step  104  the light is directed to the first surface  17   a  and the second surface  17   b . The directed light is then reflected in the fourth step  105  from the first pavement marking  51   a  and the second pavement marking  52 . The fourth step  105  reflects light measured by the light receiving means and proceeds through a fourth path  105   a  to a second decision  106  that determines whether enough light is being reflected for apparatus  10  to operate.  
         [0035]    The second decision  106  determines whether enough light is being reflected for apparatus  10  to operate. If a fifth path  106   a  is chosen then the third decision  108  determines whether the first light sensor  18   a  detects a reflectance. If a sixth path  106   b  is chosen then a fifth step  107  proceeds through the seventh path  107   a  to increase the amount of light emitted from the light sources so that a certain intensity of light is reflected to the first light sensor  18   a  and the second light sensor  18   b  as provided in the third step  104  and the fourth step  105 .  
         [0036]    When the third decision  108  does not detect reflected light the eighth path  108   a  is taken to a fourth decision  109  that determines whether the reflected light is intermittent. If the reflected light is determined not to be intermittent than a tenth path  109   a  is taken and activates an alarm  110  indicating that the driver is veering of the road. If the reflected light is determined to be intermittent than an eleventh path  109   b  is taken not activating the alarm  111 . When the third decision  108  detects reflected light is takes the ninth path  108   b  and no alarm  111  is activated. The twelfth path  11   a  is taken to the fifth decision  113  that determines if the second sensor detects reflected light.  
         [0037]    When the fifth decision  113  does not detect reflected light the thirteenth path  113   a  is taken to a sixth decision  115  that determines whether the reflected light is intermittent. If the reflected light is determined not to be intermittent than a fifteenth path  115   a  is taken and activates an alarm  110  indicating that the driver is veering of the road. If the reflected light is determined to be intermittent than a sixteenth path  115   b  is taken not activating the alarm  111 . When the fifth decision  113  detects reflected light is takes the fourteenth path  113   b  and no alarm  111  is activated.  
         [0038]    The programing structure  100  is incorporated into the controller  10   a  of apparatus  10 . At the first decision  101  a subroutine is executed. In details, the MPU  11  of the controller  10   a  determines whether or not there is enough background light for the first sensor  18   a  and the second sensor  18   b  to operate without a light source. That is to say the day/night sensor  21   a  measures how much background light is present sending a signal to the MPU  11 . The subroutine of MPU  11  determines, based upon pre-loaded information into ROM  14 , if there is enough background light to receive minimal reflected light from the surface markings to be measured by the first and second sensors.  
         [0039]    If there is not enough light then the MPU  11  sends a signal activating the first light sources  19   a  and the second light source  19   b . However, if the day/night sensor  21   a  measures to much light then the MPU  11  activates the first step  102  and reduces the amount of light being sent from the first light source  19   a  and the second light source  19   b.    
         [0040]    At the subsequent second decision  106  the MPU  11 , through a subroutine and using pre-loaded information from ROM  14 , decides whether there is enough light being reflected for the first and second sensors to operate. If there is not enough light then the MPU  11  activates the fifth step  107  and increases light to the surface markings from the light sources. As is understood by the practitioner in the art, the subroutine used by MPU  11  with programming structure  100  further receives a signal from stored data in ROM  14 . The MPU  11  provides a proper intensity range modulation so that it does not allow the light sources to be continuously activated and deactivated wherein erroneous reflected light or lack thereof would be measured by the light sensors.  
         [0041]    Once the controller  10   a  has adjusted the light source within a proper range so that the light sensors correctly measure the reflected light from the surface markings, the MPU  11  with its subroutine, RAM  13  and ROM  14  now determine if the reflectance measured by the sensors indicate whether the vehicle is veering off the road. The controller  10   a  receives a signal from the light sensors through the common bus  11   a  that feeds information to MPU  11 . As long as the light sensors continue to measure a uniform reflection of light, that is to say, the relative distance and/or angle of incidence of reflected light does not change, the subroutine of MPU  11  does not activate the alarm  16 . If the light sensors suddenly measure reflected light intensities substantially lower than previously measured then the subroutine of MPU  11  activates the alarm  16 . The subroutine allows MPU  11  to compare actual data signals received from the light sensors to recent reflected light data signals that are previously stored in the RAM  13 . The comparison, for example, enables the MPU  11  to not erroneously detect a broken pavement marking, such as a broken center line on a highway, through an algorithm stored in the ROM  14  that performs a calculation averaging the reflected light intensity. As can be seen in FIG. 2, the programming structure  100  used in the subroutine directs the MPU  11  to first determine whether the first light sensor is measuring reflected light and then directs the MPU  11  to determine whether the second light sources is measuring reflected light. In this way the alarm will be activated when the vehicles veers off the road in either direction.  
         [0042]    A light tracking apparatus is typically installed on a moving vehicle such as an automobile. A DC power source is engaged to energized the components of the light tracking apparatus. When the driver of the automobile starts it by turning on the ignition a power source engages the light tracking apparatus. The driver then can turn on or off a switch in the automobile to activate or deactivate the light tracking apparatus. Also, if the light tracking apparatus is activated, the driver can temporarily deactivate the light tracking apparatus by using a turn signal in the automobile when, for example, the driver wants to turn off the road or make a lane change. At least one light emitting means provides light projected onto a pavement marking and the surrounding background of the road. At least one light receiving means provides measurement of reflected light received from the pavement marking and surrounding background of the road. A computing means is used to process the difference between intense and weak reflected light providing a signal indicating a significant change in light intensity. Finally, an alarm means is engaged when there is a significant change in light intensity.  
         [0043]    While there has been illustrated and described what is at present considered to be the preferred embodiment of the claimed invention, it will be appreciated that numerous changes and modifications are likely to occur to those skilled in the art. It is intended in the appended claims to cover all those changes and modifications that fall within the spirit and scope of the present invention.