Abstract:
An improved vehicle safety system for transport operators designed to require the driver of a passenger vehicle to fully check the entire vehicle before exiting, thereby ensuring that no passenger is left behind. The driver is required to turn a key in the switch located at the back of the vehicle to disable the alarm. This keyed switch absolutely ensures driver compliance, much more so than conventional timers with a disable button. The system is implemented with simple and reliable relays and other components.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    The present application derives priority from U.S. Provisional Patent Application Ser. No. 61/670,396 filed 11 Jul. 2012. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to safety systems for commercial transportation operators and, more particularly, to a vehicle safety system for transport operators designed to require the driver of a passenger vehicle to fully check the entire vehicle before exiting, thereby ensuring that no passenger is left behind. 
         [0004]    2. Description of the Background 
         [0005]    The news is replete with accounts of incidents involving children inadvertently left on school buses by negligent drivers that fail to fully check the bus after dropping the other children off. As seen in  FIG. 1 , most bus operators have employee policies that require drivers to check their bus for students who might have fallen asleep, and many post signs at bus stops as a reminder. These precautions have proven ineffective at preventing the problem, and the consequences of driver inattention can be catastrophic. Children are often unable to disembark the bus on their own and can become trapped for hours. Many have suffered from heat exhaustion and dehydration, and some have died. By news accounts there were 85 such instances in 2011, and 58 so far in 2012, and many such instances are never reported. 
         [0006]    Technology offers a more effective approach to the problem, and indeed at least four states including Tennessee, Arkansas, Wisconsin and Louisiana, have laws requiring buses and daycare vehicles to have vehicle reminder systems. Such systems generally prompt the driver to check the vehicle for children before they disembark. 
         [0007]    For example, Child Safety Technologies, LLC, sells the Child Guardian Reminder System™. When the driver shuts off the vehicle, the system prompts the driver to check the vehicle for children. The driver must walk to the back of the vehicle and swipe a key card past a magnetic sensor. If the system is not reset within a predetermined amount of time an alarm goes off. 
         [0008]    U.S. Pat. No. 5,874,891 to Lowe discloses a system for reminding drivers to check for remaining passengers or articles left behind on a bus and to perform an inspection of the rear door on a bus to ensure that it is working properly. When the driver completes a run and turns off the ignition switch, the system enters an alarm state and a buzzer sounds. The buzzer is silenced only when the driver walks to the back of the bus and opens and closes the rear door. 
         [0009]    Similarly, U.S. Pat. No. 7,117,121 to Brinton et al. issued Oct. 3, 2006 discloses a system to ensure performance of mandated pre/post-trip inspections of vehicles. The system activates upon powering off the vehicle, waits a period of time for an inspection to be performed, and sounds an alarm if the inspection has not been performed. The system employs a hand-held transponder that prompts a driver to walk to the back of the bus, checking proximity to an RFID tag at the back of the bus to ensure compliance. 
         [0010]    Though the foregoing and other prior art references are far more effective than employee policies and signs, they still leave some room for driver negligence and only mitigate the risk of a sleeping child being left on the bus. Moreover, they rely on sophisticated computer electronics for determining when to sound an alarm. What is needed is a simple control system that can be wired into the existing vehicle electrical system and that imposes an analog logic scheme using relays rather than software. It would also be desirable to avoid total reliance on audible alarms. 
       SUMMARY OF THE INVENTION 
       [0011]    It is, therefore, a primary object of the present invention to provide a vehicle safety system for transport operators designed to require the driver of a passenger vehicle to fully check the entire vehicle before exiting, thereby ensuring that no passenger is left behind. 
         [0012]    It is another object to provide a failsafe vehicle safety alarm system suited for transporting young children, that relies on a combination of a door switch system, a key lock switch, and a timer mechanism, which in combination requires any vehicle driver to properly inspect his or her vehicle before leaving that vehicle for an extended period of time. 
         [0013]    It is another object to provide a vehicle safety system for transport operators that is based on inexpensive and generic components suitable for installation to a wide range of vehicles. 
         [0014]    It is still another object to provide a vehicle safety system designed to use conventional off-the-shelf (COTS) components that meet all American industrial standards and specifications. 
         [0015]    In accordance with the foregoing objects, the present invention is a vehicle safety system for transport operators designed to require the driver of a passenger vehicle to fully check the entire vehicle before exiting, thereby ensuring that no passenger is left behind. After returning from a route and turning off the ignition, the vehicle safety system arms and begins a timer countdown. Within the allotted time the driver is required to insert and turn a cylindrical key in a keyed switch located at the back of the vehicle in order to disable the alarm. Failure to timely comply activates the alarm. The vehicle safety system is wired directly to the doors of the vehicle to compel compliance, rather than just being a timer with a disable button. 
         [0016]    The foregoing design in combination with other design details to be described eliminates the risk of a sleeping child being left on the bus through driver negligence, and does so in a simple, cost-effective way that can be wired into the existing vehicle electrical system in order to physically prevent the driver from disembarking until the mandatory inspection is completed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    Other objects, features, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments and certain modifications thereof when taken together with the accompanying drawings in which: 
           [0018]      FIG. 1  is a perspective view of a bus operator fulfilling a typical policy requiring drivers to check their bus for students who have fallen asleep 
           [0019]      FIG. 2  is a schematic diagram of a vehicle safety system  2  according an embodiment of the present invention. 
           [0020]      FIG. 3  is a schematic diagram of a vehicle safety system  102  according to another embodiment the, shown in Alarm Mode. 
           [0021]      FIG. 4  is a schematic diagram of the vehicle safety system  2  as in  FIG. 3  shown in Alarm Reset Mode. 
           [0022]      FIG. 5  is a schematic diagram of a fused connection for supplying +12 (VDC) power to the relays R 1 -R 5  of  FIGS. 3-4 . 
           [0023]      FIG. 6  is a schematic diagram of a fused connection (similar to that of  FIG. 5 ) for supplying +12 (VDC) power to the relays R 1 -R 5  through a voltage divider B- 1 , when voltage regulation is needed. 
           [0024]      FIG. 7  is a schematic diagram of another embodiment of the EAC safety system  202 . This embodiment of EAC safety system  202  is implemented with digital circuitry rather than relays. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0025]    Reference will now be made in detail to preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
         [0026]    The present invention is an alarm safety system for transport operators designed to require the driver of a passenger vehicle to fully check the entire vehicle before exiting, thereby ensuring that no passenger is left behind. The alarm safety system includes an Electronic Alarm Controller (EAC) at the front of the vehicle and connected to existing vehicles wiring, and a cylindrical key switch at the rear of the bus also connected to the EAC. After returning from a route and turning off the ignition, the EAC arms itself and begins a timer countdown. Within an allotted time the driver is required to insert and turn a cylindrical key in a keyed switch at the back of the vehicle in order to disable the alarm. Failure to timely comply activates the alarm. 
         [0027]    The cylindrical key comprises a body provided with an axial bore that fits into a lock cylinder of cylindrical form that is rotatable in one angular direction. The key may be removed at one angular position of the cylinder. The key can be carried along with the vehicle ignition key on a common key ring. It is not to be left in the key switch, but is only to be used at the time the EAC is to be reset and turned off. The use of a cylindrical key and key switch is advantageous because it allows the driver to insert the key in any angular position, the coupling between the key and the key switch cylinder taking place in an angular position determined by the co-operation of a male profile of the key with a corresponding female profile of the key switch cylinder. A unique set of cylindrical keys is associated with each system described below eliminating the possibility of someone outside of the operator being able to reset the system. This ensures that each vehicle operator has control of the system. The cylindrical key switch also prevents tampering of the alarm reset function by children. In comparison with security key cards, which require electronic equipment to be installed on the vehicle, use of the present cylindrical key switch assembly in accordance with the operational logic described below facilitates a retrofit installation to typical buses that entails running only two wires from the key switch at the rear of the vehicle forward to the alarm system box at the front. 
         [0028]      FIG. 2  is a schematic diagram of a vehicle safety system according to an embodiment of the present invention. 
         [0029]    As shown at left, the safety system includes EAC  2  housed in a single enclosure mounted at the front of the vehicle, connected to the cylindrical key switch  10  at the rear of the vehicle, and also connected to existing vehicle wiring harness(es) which include: (a) 12 (VDC) battery buss; (b) vehicle (battery) ground (GND) (buss); c) a vehicle ignition (on bus), and d) the existing vehicle magnetic door switches. Typically, there are dual magnetic door-switches (DSL and DSR) which indicate front left and right door open/closed status, these being connected in series for tandem operation. Additional wiring must be installed to connect an alarm module (AL) described below (an audio and/or visual and/or voice alarm) to the EAC  2 . The existing vehicle wiring harness inclusive of the referenced lead wires can generally be accessed at a connector at the vehicle dash. 
         [0030]    Relays  22 ,  26  comprise single-pole double-throw (SPDT) non-latching relays. Relay  24  is a single-pole double-throw (SPDT) latching relay. 
         [0031]    Timer U 1  in combination with resistor bank  30 , jumper connector J 2 , variable resistor R 3  and capacitor  32 , collectively form a settable timing circuit. Timer U 1  may be a Texas instruments SA555P timer and resistor bank  30 , variable resistor R 3  and capacitor  32  create the desired time delay required. Internal jumpers in resistor bank  30  allow the time to be set to preselected times from thirty seconds up to several minutes. The use of jumper board J 2  and resistor bank  30  allows manual selection of an incremental timeframe, which helps to eliminate the possibility of someone altering the specified timeframe electronically and also adds some flexibility should the need to increase or decrease the alarm timeframe become necessary. Variable resistor R 3  provides a continuous fine adjust. 
         [0032]    In operation, the EAC  2  becomes “armed” when the ignition is turned on, and thereafter has two primary modes: Alarm Set Mode, and Alarm Reset Mode. 
         [0033]    The EAC  2  enters Alarm Set Mode upon parking the vehicle. At this point the ignition IGN is turned off and the vehicle is parked. Once the ignition IGN has been turned off, the system  2  initially outputs signal via ASD Out (which may indicate via signal light, audio alarm, or voice enunciator) to signal the driver that the EAC  2  is armed. The Alarm Mode remains in effect until the vehicle alarm is reset by insertion of the key into key switch  10  at the rear of the bus. Failure to do so by the time timer U 1  counts down sounds an alarm on Alarm Out, assuming that all doors switches D/S  1 , D/S  2 , D/S  3 , etc. are closed. If any of the doors is open, this will temporarily interrupt the Alarm Out and the alarm will turn off. However, once all doors are again closed the Alarm Out will turn back on. 
         [0034]    To implement this, +12 vdc from the vehicle power system is always applied to J 1  pin  1 . This voltage is fed to relay  22  at pin  4  and is output to pin  1  when relay  22  is in its normally closed position as shown. Relay  24  is initially in the “reset” state and so pin  12  is not initially connected to pin  7  through the relay. However, pin  1  of relay  22  is connected to pin  12  of relay  24 . Relay  24  is a latching relay. While the ignition is off the +12 vdc voltage at relay  22  pin  2  is removed causing relay  22  to reset which causes pin  4  to connect with pin  1  applying +12 vdc to pin  12  of set relay R 24 . At this point the EAC  2  is in a “state of rest” waiting for the ignition to be turned on. To arm, with the circuit connected as described above, the ignition is activated, +12 vdc voltage from ignition flows to pin  3  of the EAC  2  connector J 1 . Diode D 3  ensures that relay  22  stays “latched” once the relay  22  is set. With +12 vdc ignition voltage at relay  22  pin  2 , and ground at relay  22  pin  5 , relay  22  “sets” causing pin  3  to connect to pin  1 . Ground is now sent to pin  12  of relay  24 . In addition, LED (light emitting diode) DS 2  comes on. This LED is not visible to the driver but ensures that relay  22  has latched and is used for troubleshooting. The +12 vdc ignition voltage is also applied to the set side coil of relay  24  at pin  1  and ground is applied to realy  24  pin  3 , which causes relay  24  to set allowing the ground at pin  12  to pass through to relay  24  pin  7 . The EAC  2  is now in the “armed state” with relay  24  set, and the system is simply waiting for the ignition to be turned off. 
         [0035]    +12 vdc voltage is also sent from the vehicle electrical system to illuminate LED DS 1 . This LED DS 1  is visible outside of the EAC  2  and notifies the operator that the EAC  2  is now “armed”. 
         [0036]    After running a route the vehicle is parked the ignition key is turned off, and the EAC  2  advances to Alarm Set Mode. +12 vdc ignition is removed from J 1 - 3 , relay  22  resets, +12 vdc is now sent to pin  12  of relay  24 . Furthermore, the +12 vdc voltage is sent to the delay timer U 1  and to the resistor selection bank  29  and an Alarm Reset countdown begins. The countdown is manually programmable. Jumper board J 2  may be set to any incremental resistor R 4 -R 11  and any incremental delay time, e.g., selecting resistor R 6  selects a delay time of  60  seconds. Capacitor C 2  is coupled with the selected resistor of selection bank  29  to determine the time delay threshold for the output of the delay timer U 1  to become active while C 1 , R 1  and R 3  determine the trigger. At this point the only output which is “active” (plus voltage) is pin  5 . The EAC module  2  pin  6  is currently at ground through the closed contacts of relay  26 . If the time threshold for U 1  is reached without the driver manually resetting the EAC system, the output pin  3  of U 1  goes to ground, causing relay  26  to “activate” (putting +12 vdc voltage out) on pin  6  (Alarm Out) of the EAC module. 
         [0037]    The EAC  2  preferably also employs the vehicle&#39;s existing door switches as part of the functionality. Specifically, the ground for Alarm Out is routed through each of the door switches D/S  1 , D/S  2 , D/S  3 , etc., in series. This effectively prevents the system from signaling an alarm on Alarm Out if one or more of the doors is open. Assuming that all doors switches D/S  1 , D/S  2 , D/S  3 , etc. are closed, the EAC  2  is capable of fully arming. At this time the ASD Out at pin  5  of the EAC  2  goes off notifying the operator (by light, sound or digital voice) to reset the alarm system within the predetermined countdown. 
         [0038]    The EAC  2  remains in the fully armed state until the Alarm Reset Key  10  is activated. To disable the Alarm Out and ASD Out before or after it sounds the Alarm Reset Key  10  is engaged by the operator, causing +12 vdc voltage to be applied to Alarm Reset Key  10  at J 1  pin  4  of the EAC module  2 , which in turn causes relay  24  to latch to the “reset” state, thereby removing the +12 vdc plus voltage from output pin  5  of the EAC  2  and also generating a reset to pin  4  of the delay timer U 1 . The removal of the +12 vdc voltage from the coil of relay  26  causes it to reset and the output to pin  6  of the EAC is returned to ground causing the Alarm Out at J 1  pin  6  to shut off. The EAC is now in the “fully reset state” and is once more awaiting for the ignition switch to be engaged. Until that occurs the EAC module  2  will remain in this state. 
         [0039]    The EAC  2  is also disabled if any of the doors is opened to a sufficient amount (more than 1 inch typical). However, simply opening a door does not reset the EAC  2  and the alarm will still sound when said door(s) is (are) closed properly. The only means to reset the alarm after the EAC  2  has reached the fully armed state is via the Alarm Reset Key  10 . 
         [0040]    Prior to the EAC  2  reaching the “fully armed” state the EAC will return to the armed state by simply turning the vehicle ignition switch off. This allows the operator to perform multiple vehicle restarts without having to engage the Alarm Reset Key  10  after each restart. This is possible because although relay  24  is now in the “set” state the output of relay  24  is controlled by the input to relay  22  which will be ground whenever the ignition is in the OFF state. However, whatever is connected to the Audio Sound Device/Auxiliary output pin  5  will become active whenever the ignition is in the OFF state just as described above. This is due to the EAC module  2  “detecting” the vehicle to be in OFF state. If the operator does not perform a restart of the ignition or a reset via Alarm Reset Key  10  within the preselected timeframe the Alarm will trigger as designed. 
         [0041]    Certain operational features are designed to facilitate a normal school route wherein the vehicle must be stopped numerous times without inventorying the back of the vehicle and fully resetting the alarm. So long as the engine is running, the vehicle alarm  2  remains disabled. If the driver must stop for a short period of time, leaving one of the doors open that has a magnetic door switch installed, this will prevent the alarm from sounding. If the driver decides to leave the key in the ignition in the run position with the engine off, the driver can simply start the engine from the ignition key run position and continue his trip without having to reset the vehicle alarm  2 . Alternatively, as noted above, the driver may wish to temporarily reset the vehicle alarm system using the vehicle ignition key. For a temporary reset, while stopped, the driver must leave the ignition key in the run position, without turning on the engine. With the ignition key in the on position, this will initiate the Alarm Reset Mode. 
         [0042]      FIGS. 3-4  are schematic diagrams of a vehicle safety system  102  according to another embodiment,  FIG. 3  showing system  102  in Alarm Mode and  FIG. 4  in Reset Mode. 
         [0043]    This embodiment of EAC safety system  102  is implemented with two standard double-pole double throw (DPDT) relays R 1  &amp; R 2 , two double-pole (double-throw (DP/DT) latching relays R 3  &amp; R 4 , and a double pole/double throw (DP/DT) timer relay R 5 , an alarm reset key ARK, an alarm module AL, and a driver alarm light DAL. The activation coil of the DPDT relay R 1  is connected to the vehicle ignition lead and to ground. The activation coil of the DPDT relay R 2  is connected to the vehicle ignition lead for selectively connecting lead R 1   7  to R 1   1  or R 1   4 , and in tandem connecting lead R 1   9  to R 1   3  or R 1   6 . The activation coil of the DPDT relay R 2  is connected between R 1   4  and ground for selectively connecting lead R 2   7  to R 2   1  or R 2   4 , and in tandem connecting lead R 2   9  to R 2   3  or R 2   6 . The activation coil of the DPDT latching relay R 3  is connected between R 2   1  and R 2   3  for selectively connecting lead R 3   7  to R 3   1  or R 3   4 , and in tandem connecting lead R 3   9  to R 3   3  or R 3   6 . The activation coil of the DPDT latching relay R 4  is connected between R 3   4  and R 3   6  for selectively connecting lead R 4   7  to R 4   1  or R 4   4 , and in tandem connecting lead R 4   9  to R 4   3  or R 4   6 . The activation coil of the DPDT timer relay R 5  is connected between R 4   6  and GND for selectively connecting lead R 5   7  to R 5   1  or R 5   4 , and in tandem connecting lead R 5   9  to R 5   3  or R 5   6 , in both cases after a predetermined interval. Alarm reset key Alarm Reset Key  10  is a keyed single-pole single-throw SPST cylindrical key switch that is connected to +12 VDC (KHB), and operable to connect the activation coil of the DPDT relay R 1  in series with ground, thereby activating R 1 . 
         [0044]    Alarm module AL is a visual and/or audio alarm module connected in series between R 5   4  and the series-connected door-open leads DSL and DSR for sounding or indicating an alarm. Driver alarm light DAL is as stated and is connected between R 4   4  and ground. 
         [0045]    As above, the vehicle safety system has two primary modes: Alarm Set Mode, and Alarm Reset Mode. The system  102  enters Alarm Set Mode upon parking the vehicle. At this point the ignition key KHB is turned off and the vehicle is parked. Once the ignition key KHB has been turned off, the system  102  will advance to the Alarm Set Mode, and +12 (VDC) is removed from energizing coil of relay R 1 . This de-energizes R 1  and opens contacts R 1   7  to R 1   4  (as shown in  FIG. 3 ) providing no voltage to the energizing coil of R 2 . R 2  becomes de-energized, connecting R 2   7  and R 2   1  and providing a ground path to the bottom of the R 3  energizing coil. R 2   9  is connected to R 2   3  and this provides +12 (VDC) to the top of the R 3  energizing coil. Latching relay R 3  now becomes energized and moves to an un-latch position, remaining in the un-latch position for the remainder of the alarm set process. In this position R 3   7  is connected to R 3   4  (as shown) to provide a GND path to the bottom of the latching relay R 4  energizing coil. R 3   9  is connected to R 3   6  to provide +12 (VDC) to the top of the R 4  energizing coil. Consequently, latching relay R 4  now becomes energized and moves into an un-latch position. R 4  remains in the un-latch position for the remainder of the Alarm Set Mode. In this position R 4   7  is connected to R 4   4  as shown to provide a +12 VDC signal to the driver alarm light DAL, which illuminates. R 4   9  is connected to R 4   6  provide a +12 VDC to the energizing coil of R 5 . Timer relay R 5  now becomes energized. Timer relay R 5  begins to count down a preset time period, for example, 3 minutes. If the alarm system  102  is not reset by the driver in time, the timer relay R 5  will throw and turn on the alarm module AL. When timer relay R 5  throws, R 5   7  is connected to R 5   4  to provide +12 (VDC) to the (+) terminal of the alarm module AL. Alarm module AL is connected in series with the series-connected door magnetic switch leads DSL and DSR. Simultaneously, R 5   9  is connected to R 5   6 , thereby providing a GND path to the series-connected door (switch) leads DSL and DSR and AL. Current flows through alarm module AL and provides an audio alarm. The Alarm Mode remains in effect until the vehicle alarm is reset (as will be described). Note that if either of the doors is forced open, this will temporarily interrupt the AL circuit and the alarm will go off. However, once all doors are again closed the AL alarm will turn back on. 
         [0046]    The alarm system  102  may be temporarily reset by the driver turning the vehicle ignition key to the “on” position without starting the engine, or may be permanently reset by taking the alarm reset key ARK to the back of the bus, inserting it into the keyed single-pole single-throw SPST switch and turning. This applies power to the activation coil of R 1  and resets the alarm as described in the reset operation below. 
         [0047]    The vehicle alarm system  102  reset configuration is shown in  FIG. 4 . For a permanent reset the ignition key must be turned off. The driver must push the key switch  10  into the keyed slot at the back of the bus and turn the ARK key clockwise for a short period. The key switch  10  is a momentary (spring return) cylindrical key switch, as described above, that connects +12 VDC power to the top of R 1  energizing coil. The bottom of the R 1  coil is already connected to GND. While the key switch  10  is held in the reset position this energizes the R 1  coil for a short period of time, connecting R 1   7  and R 1   4  to provide +12 (VDC) to the top of the R 2  energizing coil, the bottom of the R 2  coil already being connected to GND. R 2  likewise energizes for a short period of time, and R 2   7  is connected to R 2   4  to provide a GND path to the top of the R 3  energizing coil for a short period of time. R 2   9  is connected to R 2   6  to provide +12 VDC to the bottom of the R 3  energizing coil for a short period of time. R 3  becomes energized and moves into its latch position from the un-latch position. R 3  will now remain in the latch position for the remainder of the Alarm Reset Mode. The key can now be removed from key switch  10 . R 3   7  is connected to R 3   1  to provide a GND path for the top of the R 4  energizing coil. R 3   9  is connected to R 3   3  to provide +12 VDC to the bottom of the R 4  energizing coil. This energizes R 4  and moves it into the latch position from the un-latch position. As with R 3 , R 4  will now remain in the latch position for the remainder of the Alarm Reset Mode. R 4   7  is disconnected from R 4   4  removing +12 VDC power from the driver alarm light DAL, which extinguishes. R 4   9  is disconnected from R 4   6  removing the +12 VDC power from the top of the R 5  energizing coil. R 5  becomes de-energized. R 5   7  is disconnected from R 5   4  removing the +12 VDC power from the AL alarm module. R 5   9  is disconnected from R 5   6  removing the GND path from the door switch leads DSL and DSR. The vehicle alarm system  102  is effectively reset and turned off at this point. 
         [0048]    As above, certain operational features are designed to facilitate a normal school route wherein the vehicle must be stopped numerous times without inventorying the back of the vehicle and fully resetting the alarm. So long as the engine is running, the vehicle alarm  2  remains disabled. If the driver must stop for a short period of time, leaving one of the doors open that has a magnetic door switch installed, this will prevent the alarm from sounding. If the driver decides to leave the key in the ignition in the run position with the engine off, the driver can simply start the engine from the ignition key run position and continue his trip without having to reset the vehicle alarm  2 . Alternatively, as noted above, the driver may wish to temporarily reset the vehicle alarm system using the vehicle ignition key. For a temporary reset, while stopped, the driver must leave the ignition key in the run position, without turning on the engine. With the ignition key in the on position, this will initiate the Alarm Reset Mode. The +12 (VDC) signal is applied to the top of the energizing coil of R 1  and remains there until the ignition key is turned off again. The bottom of the R 1  energizing coil is already connected to GND, and so R 1  becomes energized. R 1   7  is connected to R 1   4  to provide a +12 (VDC) signal to the top of R 2 . The bottom of the R 2  energizing coil is already connected to GND, and so R 2  becomes energized. R 2   7  is connected to R 2   4  providing a GND signal to the top of the R 3  energizing coil. R 2   9  is connected to R 2   6  to provide +12 (VDC) power to the bottom of the R 3  energizing coil. This energizes R 3  which moves into the latch position from the un-latch position. R 3  remains in the latch position for the remainder of the Alarm Reset Mode. R 3   7  is connected to R 3   1  to apply GND to the top of the R 4  energizing coil. R 3   9  is connected to R 3   3  to provide a +12 (VDC) signal to the bottom of the R 4  energizing coil. This energizes R 4 , which moves into the latch position from the un-latch position. As with R 3 , R 4  will now remain in the latch position for the remainder of the Alarm Reset Mode. R 4   7  is disconnected from R 4   4  removing +12 (VDC) power from the driver alarm light DAL, which extinguishes. R 4   9  is disconnected from R 4   6  removing the +12 (VDC) power from the top of the R 5  energizing coil. R 5  becomes de-energized. R 5   7  is disconnected from R 5   4  removing the +12 (VDC) power from the AL alarm module. R 5   9  is disconnected from R 5   6  removing the GND path from the door switch leads DSL and DSR The vehicle alarm system  102  is temporarily reset at this point. So long as the ignition key is used to start the engine, the vehicle alarm system  102  will remain turned off. However, if the ignition key is turned off and/or removed from the vehicle, the alarm system will reinitiate the process of turning the alarm back on via Alarm Set and Alarm Mode described above. 
         [0049]      FIG. 5  is a schematic diagram of a fused connection for supplying +12 (VDC) power to the relays R 1 -R 5  as shown in  FIGS. 3-4 . The +12 (VDC) is taken from the on-board vehicle battery and run through a fuse F- 5 , through the existing vehicle ignition relay P 1  and to relays R 1 -R 5 . 
         [0050]    In some cases a level of voltage regulation may be required for proper voltage bias or to avoid relay chatter.  FIG. 6  is a simple schematic diagram of a fused connection (similar to that of  FIG. 5 ) for supplying +12 (VDC) power to the relays R 1 -R 5  through a voltage divider B- 1  comprising a pair of resistors arranged in series. The regulated voltage is picked from between the series resisters B- 1  as shown and used for powering relays R 1 -R 5 . The value of the pair of resistors is a matter of design choice depending on the other component requirements. 
         [0051]      FIG. 7  is a schematic diagram of another embodiment of the EAC safety system  202 . This embodiment of EAC safety system  202  is implemented with digital circuitry rather than relays. As above, the vehicle safety system has two primary modes: Alarm Set Mode, and Alarm Reset Mode. The system  202  enters Alarm Set Mode upon parking the vehicle. At this point the ignition key KHB is turned off and the vehicle is parked. Once the ignition key KHB has been turned off, the system  202  will advance to the Alarm Set Mode, and +12 (VDC) is removed from pin TB- 3  of electronic reset module  222 . Electronic reset module  222  is a combinatorial logic circuit that outputs reset logic “ 1 ” given a +12 vdc on J 1 - 1  to TB- 1  and no signal (ignition KHB off) on TB- 3 . A reset logic “1” output from module  222  arms electronic preset module  224  and also triggers a digital timer  225  (with optional short circuit protection) as shown). Preset module  224  initially signals a driver alarm LED and optional ASD alarm such as a voice enunciator, to signal the driver that the EAC  202  is armed. The Alarm Mode remains in effect until the vehicle alarm is reset by insertion of the ARK switch at the rear of the bus. Failure to do so by the time digital timer  225  counts down a programmable countdown sounds an alarm on ALARM OUT  229 , assuming that all doors switches D/S  1 , D/S  2 , D/S  3 , etc. are closed. Again, if any of the doors is forced open, this will temporarily interrupt the ALARM OUT  229  circuit and the alarm will turn off. However, once all doors are again closed the AL alarm will turn back on. 
         [0052]    The EAC EAC  202  may be temporarily reset by the driver turning the vehicle ignition key to the “on” position without starting the engine, or may be permanently reset by taking the alarm reset key ARK to the back of the bus, inserting it into the keyed single-pole single-throw SPST switch and turning. This applies power to TB- 4  of module  222  and resets the alarm as described in the reset operation below. The Alarm Mode remains in effect until the vehicle alarm is reset (as will be described). The EAC  202  may be temporarily reset by the driver turning the vehicle ignition key to the “on” position without starting the engine, or may be permanently reset by taking the alarm reset key ARK to the back of the bus, inserting it into the keyed single-pole single-throw SPST switch and turning. So long as the engine is running, the vehicle alarm  202  remains disabled. If the driver leaves a magnetic door switch open this will prevent the alarm from sounding. The driver may wish to temporarily reset the vehicle alarm system using the vehicle ignition key by leaving the ignition key in the run position, without turning on the engine. The vehicle EAC  202  is temporarily reset at this point. So long as the ignition key is used to start the engine, the vehicle EAC  202  will remain turned off. However, if the ignition key is turned off and/or removed from the vehicle, the alarm system will reinitiate the process of turning the alarm back on via Alarm Set and Alarm Mode described above. 
         [0053]    It should now be apparent that the above-described EAC alarm system of embodiments  2 ,  102 ,  202  eliminate the risk of a sleeping child being left on the bus through driver negligence, and does so in a simple, cost-effective way using a retrofittable relay network that can be wired into most any existing vehicle electrical system. 
         [0054]    Those skilled in the art will understand that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. It is to be understood, therefore, that the invention may be practiced otherwise than as specifically set forth in the appended claims.