Patent Publication Number: US-2016237690-A1

Title: Systems and methods for monitoring use of rail on a footpath

Description:
If an Application Data Sheet (“ADS”) has been filed on the filing date of this application, it is incorporated by reference herein. Any applications claimed on the ADS for priority under 35 U.S.C. §§119, 120, 121, or 365(c), and any and all parent, grandparent, great-grandparent, etc., applications of such applications, are also incorporated by reference, including any priority claims made in those applications and any material incorporated by reference, to the extent such subject matter is not inconsistent herewith. 
     CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of the earliest available effective filing date(s) from the following listed application(s) (the “Priority Applications”), if any, listed below (e.g., claims earliest available priority dates for other than provisional patent applications or claims benefits under 35 USC §119(e) for provisional patent applications, for any and all parent, grandparent, great-grandparent, etc. applications of the Priority Application(s)). 
     PRIORITY APPLICATIONS 
     None 
     If the listings of applications provided above are inconsistent with the listings provided via an ADS, it is the intent of the Applicant to claim priority to each application that appears in the Domestic Benefit/National Stage Information section of the ADS and to each application that appears in the Priority Applications section of this application. 
     All subject matter of the Priority Applications and of any and all applications related to the Priority Applications by priority claims (directly or indirectly), including any priority claims made and subject matter incorporated by reference therein as of the filing date of the instant application, is incorporated herein by reference to the extent such subject matter is not inconsistent herewith. 
     TECHNICAL FIELD 
     The field of the present disclosure relates generally to safety systems for a footpath or pathway, and in particular, to such safety systems for monitoring use of a safety rail that borders the footpath to prevent injuries or falls while moving along the footpath. 
     SUMMARY 
     The present disclosure describes various embodiments for safety systems and methods of use for monitoring use of a safety rail that borders a footpath (such as a staircase, a ramp, a walkway, a hallway, or other pathway) to help a human user move along the footpath while avoiding potential injury. For example, in one embodiment, the safety system includes a sensor system operatively coupled with the safety rail and the footpath, where the sensor system is configured to detect a presence of the human user within an activation field of the sensor system and track a movement speed of the user moving along the footpath. The sensor system converts the detected presence of the user into a footpath presence signal. The safety system may further include a mobile barrier system or platform including a mobile barrier that is extendable to cross or block a travel route of the footpath, where the mobile barrier is configured to move along the safety rail at substantially the movement speed of the user in advance of the user. 
     In some embodiments, the sensor system (or a second sensor system) is further configured to detect the presence and/or absence of contact by the user on the safety rail and generate a safety rail contact signal in response to detecting or not detecting contact. The sensor system may include one or more sensors suitable for detecting the presence of the human user on the footpath and for detecting contact between the user and the safety rail, such as optical sensors, infrared sensors, acoustics sensors, pressure sensors or any other suitable sensor. 
     In such embodiments, the mobile barrier may be configured to lock in position upon receipt of the footpath presence signal and the safety rail contact signal indicating that the human is concurrently moving on the footpath without making contact with the safety rail. The mobile barrier helps ensure that the user cannot walk along footpath (e.g., walk down the stairs) unless the user is contacting or holding on to the rail. When the user contacts the rail, the barrier may retract away to allow the user to continue walking along the footpath. In some embodiments, the barrier may be self-propelled and move along the footpath at a predetermined constant speed or at a speed calculated to match the moving speed of the user along the footpath. In such embodiments, the barrier may serve both as a block to remind the user to hold on to the safety rail before entering the footpath, and as an aid that may be used to physically support the user (e.g., the user may hold on to the barrier) as the user walks along the footpath. 
     In some embodiments, the sensor system may include one or more sensors arranged and supported by the safety rail, where the sensors are configured to detect a touch and/or to detect a grip pressure between the human user and the safety rail. The rail sensors may help determine not only that the user is contacting the safety rail, but also that the user is gripping the safety rail with sufficient strength to properly support the user while walking on the footpath. In such embodiments, contact information detected by the sensors on the safety rail is communicated via the safety rail contact signal. 
     In some embodiments, the footpath presence signal and the safety rail contact signal are communicated to a sensor observation system that is in operative communication with the sensor system. The sensor observation system receives both signals and generates a warning signal or alert signal when the signals indicate that the human is concurrently present on the footpath without contacting the safety rail, or without gripping the safety rail with sufficient grip force above a predetermined force threshold. For example, when the human user begins walking up or down a staircase without immediately (or shortly after entering the staircase) holding on to the safety rail, the warning signal is generated to warn or command the user to hold the safety rail. In some embodiments, the warning signal or alert signal may be a visual signal that the user may perceive or an audible signal or tone that the user may hear. For example, the alert signal may be an synthesized speech (such as a command), a buzzer sound, or a visible light, among other signals. 
     Additional details of these and other embodiments are described further below with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a safety rail monitoring system for monitoring a footpath with a plurality of footpath presence sensors, according to one embodiment. 
         FIG. 2  is a partial cut-away view of the footpath illustrating another embodiment of a safety rail monitoring system. 
         FIG. 3  is a partial cut-away view of the footpath illustrating an automatic identification and data capture system for monitoring the footpath, according to one embodiment. 
         FIG. 4  is a partial cut-away view of the footpath illustrating a camera system for monitoring the footpath, according to one embodiment. 
         FIG. 5  is a partial cut-away view of the footpath illustrating one embodiment of a sensor observation system for communicating an alert signal to the user. 
         FIG. 6  is a partial cut-away view of the footpath illustrating another embodiment of a sensor observation system. 
         FIG. 7  illustrates a moveable barrier positioned along the footpath for impeding progress of the user along the footpath, according to one embodiment. 
         FIG. 8  is a block diagram illustrating a method for monitoring use of a safety rail bordering a footpath, according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS 
     With reference to the drawings, this section describes particular embodiments of various safety systems and their detailed construction and operation. Throughout the specification, reference to “one embodiment,” “an embodiment,” or “some embodiments” means that a particular described feature, structure, or characteristic may be included in at least one embodiment of the safety system. Thus appearances of the phrases “in one embodiment,” “in an embodiment,” or “in some embodiments” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the described features, structures, and characteristics may be combined in any suitable manner in one or more embodiments. In view of the disclosure herein, those skilled in the art will recognize that the various embodiments can be practiced without one or more of the specific details or with other methods, components, materials, or the like. In some instances, well-known structures, materials, or operations are not shown or not described in detail to avoid obscuring aspects of the embodiments. 
     In the following description, the terms “footpath” and “staircase” may be used interchangeably to refer to an example pathway for which the safety system may be used. In addition, the accompany drawings illustrate the footpath as being a staircase in some example embodiments. It should be understood that a staircase is only one example of a footpath that may be monitored with the safety system described below and is not intended to be limiting. The staircase is merely used for illustration purposes in the written description and the accompanying figures. 
       FIGS. 1-8  collectively illustrate various embodiments of a safety rail monitoring system  100  for monitoring use of a safety rail  105  that borders a footpath  110  to help a user  115  travel along the footpath  110  and avoid tripping or falling while walking on or along the footpath  110 . As is discussed in further detail below, the safety rail monitoring system  100  includes a sensor system  120  that monitors the presence and movement speed of the user  115  along the footpath  110  and determines whether the user  115  is holding on to or contacting a safety rail  105  arranged along the footpath  110 . The safety system  100  further includes a mobile barrier system  750  including a mobile barrier  700  that extends across a travel route along the footpath  110 , where the mobile barrier  700  is configured to move along or adjacent to the safety rail  105  at substantially the movement speed of the user in advance of the user (see  FIG. 7 ). If the sensor system  120  determines that the user  115  is present on the footpath  110  but is not holding or contacting the safety rail  105 , then a sensor observation system  160  generates an alert signal or warning to remind the user  115  to hold the safety rail  105  for the safety of the user  115 . Upon being alerted, the user  115  may hold the safety rail  105  and continue walking along the footpath  110  to avoid possible injury. Once the user  115  holds the safety rail  105 , the barrier  700  may move along the footpath  110  in advance of the user  115 . 
     As mentioned previously, it should be understood that while the footpath  110  is illustrated as a staircase in the figures, a staircase is only one example of a footpath  110  and not intended to be limiting. In other embodiments, the footpath  110  may be a ramp, a hallway, a walkway, balcony, escalator, overpass, walkway (such as near a fall or a waterway), or any other suitable pathway. The following section describes additional details of these and other embodiments of the safety rail monitoring system  100 . 
     With particular reference to  FIG. 1 , the safety rail monitoring system  100  includes a sensor system  120  operatively coupled with a safety rail  105  and a footpath  110 . The sensor system  120  is configured to detect the presence of the user  115  on the footpath  110 , and to detect a contact presence or absence between the user  115  and the safety rail  105  (e.g., to detect whether or not the user  115  is holding on to the safety rail  105 ). In some embodiments, the sensor system  120  may include a first sensor subsystem  125  operatively coupled to or arranged along the footpath  110 , and a second sensor subsystem  130  operatively coupled to the safety rail  105 . Both the first and second sensor subsystems  125 ,  130  may be in communication with one another and share various components, or they may be separate, independent systems. 
     With reference to  FIG. 1 , the first sensor subsystem  125  may be coupled to or arranged along the footpath  110  and may comprise one or more individual footpath presence sensors  135 . Preferably, at least one footpath presence sensor  135  is positioned near or adjacent an entry of the footpath  110  and at least one other footpath presence sensor  135  at an exit of the footpath  110  to detect the user&#39;s  115  approach from either side of the footpath  110 . For example, as illustrated in  FIG. 1 , the footpath sensor  135   a  may be positioned proximal to or at an entry apron  140  (e.g., at an initial step or beginning portion of the staircase), and another footpath presence sensor  135   b  may be positioned proximal to or at an exit apron  145  (e.g., a final step or exit portion) of the footpath  110 . In such embodiments, the first sensor subsystem  125  detects the user  115  as the user enters the footpath  110  near the entry apron  140  (e.g., the user begins walking down the staircase), and detects the user  115  at the exit apron  145  when leaving the footpath  110  (e.g., the user walks away from the staircase after reaching the lower level). 
     As mentioned previously, the first sensor subsystem  125  also includes a plurality of footpath presence sensors  135  positioned along the footpath  110 . The footpath presence sensors  135  may be arranged in a variety of configurations along the footpath  110 . For example, in one embodiment, the footpath  110  may be a staircase and each stair may include an individual footpath presence sensors  135  coupled to each stair (such as on the risers) or attached adjacent the stair. In some embodiments, a single footpath presence sensor  135  may monitor multiple stairs to reduce the number of total sensors  135  needed to monitor the footpath  110 . In other embodiments, the sensors  135  may be positioned underneath the footpath  110  so that they are activated when the user  115  walks on the sensors  135  (e.g., weight sensors). In still other embodiments, the sensors  135  may be arranged in a different configuration, such as distributed at specific distance intervals along a footpath  110  or arranged underneath sections of the footpath  110  (such as weight or pressure sensors). Collectively, these sensors  135  are configured to detect the presence of the user  115  along a travel route extending from the entry apron  140  to an exit apron  145  of the footpath  110 . In other words, the sensors  135  detect the user  115  while the user is traveling on the footpath  110 , such as when the user is walking up or down the stairs. 
     Any one of a variety of sensors capable of detecting the presence of the user  115  may be suitable for use. For example, in some embodiments, the footpath presence sensors  135  may include any of the following: optical sensors, acoustic sensors, infrared sensors, photocell sensors, ultrasonic sonar sensors, radar sensors, micro-impulse radar sensors, proximity sensors, pressure sensors/plates, weight sensors, microwave sensors, motion sensors, Doppler sensors, or any other active or passive sensors. It should be understood that in some embodiments, the sensors  135  of the sensor system  120  may not all be of the same kind or type of sensors. For example, the footpath presence sensors  135  near the entry apron  140  and the exit apron  145  may be optical sensors, and the footpath presence sensors  135  on or along the footpath  110  may each be pressure sensors. 
     In some embodiments, the footpath presence sensors  135  may include one or more light curtains  235  for monitoring the footpath  110  and detecting the presence of the human user  115  within the footpath  110  (see  FIG. 2 ). With reference to  FIG. 2 , in one embodiment, a light curtain  235  may be positioned on or near and traversing the entry apron  140  of the footpath  110 , and additional light curtains  235  may be on or adjacent individual steps of the footpath  110  and traversing those steps. Although light curtains  235  are illustrated only on portion of the footpath  110 , it should be understood that the light curtains  235  may be arranged on each step of the footpath  110 , including the exit apron  145 , so that each step has a corresponding light curtain. In other embodiments, the light curtains  235  may be arranged in different configurations. 
     With particular reference to  FIG. 2 , the light curtains  235  comprise one or more transmitters  240  and receivers (such as photoelectric cells), each of the transmitters  240  projecting one or more light beams  245  toward the receivers (not shown) so that the light beams  245  travel across a width of the footpath  110 . Preferably, the light beams  245  are infrared light beams so that they are not visible to the user  115  for aesthetic purposes, but may be other types of light beams. In some embodiments, the light curtains  235  may further include one or more reflectors (not shown) configured to reflect light from one of the transmitters  240  to one or more of the receivers; for example, the receivers and transmitters can both be located on the same side of the footpath, with reflectors placed on the opposite side. When the light curtains  235  are triggered (e.g., a user  115  traverses one or more light beams  245 ), the sensor system  120  generates the footpath presence signal in response to the human user  115  triggering the light curtains  235 . Additional details of these and other embodiments are discussed below. 
     In some embodiments, the light curtains  235  may be capable of distinguishing between a human user  115  and any other mobile object (such as a pet, ball, toy, etc.) that may be present or moving on the footpath  110  by arranging the light beams  245  at different heights above the footpath  110  and monitoring the light beams  245  that are traversed or interrupted. For example, in one embodiment, the light beams  245  of the light curtain  235  may be arranged so that the topmost light beam  245  is at a height of at least two to three feet and up to eight feet or more above the surface level of the footpath  110  (e.g., as measured from a top surface of the corresponding step). In such embodiments, it is highly likely that when the topmost light beam  245  is interrupted, it signals that a human user  115  is moving in the pathway since a cat, a dog, or other pet likely are not tall enough to interrupt the topmost light beam  245  if it is set at two or three feet. In other embodiments, the topmost light beam  245  may be set at a height of at least three to four feet or higher to minimize the risk that a dog (or a dog&#39;s tail) may interrupt the topmost light beam  245 . In addition, by tracking and monitoring the interruption of light beams of successive light curtains  235  positioned throughout the footpath  110 , the safety rail monitoring system  100  may determine a position, a direction of motion, and a speed of motion of the human user  115  on the footpath  110 . 
     With reference to  FIG. 2 , the following section briefly describes an example operation process using the light curtains  235 . In one example, the sensor system  120  monitors the various light beams  245  of the light curtains  235 . When the topmost light beam  245  of the light curtain  235  on the entry apron  140  is triggered, this indicates that a human user  115  has entered the footpath  110  (e.g., a user  115  is going down the stairs). At this point, the sensor system  120  (or the light curtains  235 ) generates the footpath presence signal indicating that the user  115  has entered the footpath  110 . However, if a pet or other object enters the footpath  110 , the pet or object may interrupt one or more beams  245  of the light curtains  235 , but will likely not interrupt the top most light beam  245 . Accordingly, since the topmost light beam  245  is not interrupted, the sensor system  120  will not generate any signal. 
     In other embodiments, the footpath presence sensors  135  may include or comprise an automatic identification and data capture (AIDC) system positioned proximal to the footpath  110  to automatically detect the user  115  as the user enters the footpath  110 . With reference to  FIG. 3 , the AIDC system may include a tag  300 , such as an radio frequency identification (RFID) tag or a tag readable by a machine-vision system, and a tag reader  305 , such as an RFID reader configured to detect the RFID tag  300  or a machine-vision system for reading the tag  300 . The tag  300  may be carried by the user  115  (such as in a pants pocket, shirt pocket, included or embedded in clothing worn by the user, or embedded in an electronic device, such as a phone), wherein the tag reader  305  is configured to detect the tag  300  and capture data from the tag  300  to detect the presence of the user  115  within the footpath  110 . Preferably, the tag  300  includes identification and other information for its wearer/carrier. For example, the tag  300  carried by the user  115  may include some or all of the following information: (a) the name of the user  115 ; (b) physical issues or injuries that may impair the user&#39;s  115  ability to walk, such as the user&#39;s  115  impaired vision, blindness, leg injury, age, etc.; (c) preferences regarding preferred alert signal, such as auditory, visual, spoken commands, etc.; and (d) preferences regarding preferred system settings, such as whether the system should be operative for user  115 , what grip strength is required, what fraction of time or travel distance safety rail contact must be maintained, whether or how an existing physical barrier should be operated for user  115 , etc. 
     With reference to  FIG. 3 , one tag reader  305  may be positioned proximal to the entry apron  140  of the footpath  110 , and another tag reader (not shown) may be positioned proximal to the exit apron  145  of the footpath  110  to detect the presence of the tag  300  as the user  115  enters/exits the footpath  110  from either end. In some embodiments, the sensor system  120  may include a plurality of tag readers  305  arranged at various positions along the travel route of the footpath  110  to detect the presence of the tag  300  and position of the user  115  as the user moves along the footpath  110  between the entry and exit aprons  135 ,  140 . 
     The tag  300  and tag reader  305  may be any one of a variety of suitable devices. For example, in one embodiment, the tag  300  may be a beacon emitting radiation and the tag reader  305  may be a detector for the radiation. The radiation may comprise at least one of ultrasonic radiation, radio frequency radiation, infrared radiation, visible radiation, or ultraviolet radiation. In some embodiments, the tag  300  may be an RFID tag, such as an active RFID tag, and the tag reader  305  may be an RFID reader. The RFID tag may be an active or passive RFID tag, and the RFID reader may be an active or passive RFID reader. Preferably, the RFID reader has a reception range overlapping the footpath  110 . 
     In one embodiment, the RFID tag  300  may be an active RFID tag  300  and the tag reader  305  may be a passive RFID reader  305  configured to receive a signal from the active RFID tag  300 . In other embodiments, the RFID tag  300  may instead be a passive RFID tag  300  and the RFID reader  305  may instead be an active RFID reader  305  configured to transmit interrogatory signals and receive data from the passive RFID tag. In yet other embodiments, RFID tag  300  is an active RFID tag  300  and the tag reader  305  is an active reader  305  configured to transmit interrogatory signals, wherein the RFID tag  300  is activated in response to receiving the interrogatory signal. 
     In some embodiments, the RFID reader  305  may have a fixed interrogatory zone overlapping the footpath  110 , where the RFID reader  305  is configured to transmit interrogatory signals within the interrogatory zone and receive data from the RFID tag  300  when the RFID tag  300  is positioned within the interrogatory zone. In such embodiments, the RFID tag  300  may be carried by the human user  115 , and the sensor system  120  may generate the footpath presence signal in response to the RFID reader  305  receiving a signal from the RFID tag  300  indicating that the human user  115  is positioned within the interrogatory zone. 
     In other embodiments, the sensor system  120  may be in communication with smart apparel (e.g., apparel in communication with the sensors of the first sensor system) worn by the user  115  to detect the presence of the user  115  within the footpath  110 , and to also detect movement and position information of the user  115 . In still other embodiments, the sensor system  120  may be in communication with an electronic device (not shown), such as a mobile phone, personal data assistant (PDA), an electromagnetic transmitter, an ultrasonic transmitter, or other suitable device, carried by the user  115 . The electronic device may include a position determination system, such as a GPS or environmental tracking system, configured to generate position information and communicate the information to the first sensor system  120 . With this information, the first sensor system  120  may be able to detect the user  115  and track movement of the user  115  through the footpath  110 . As is further described in detail with respect to the sensor observation system  160 , motion and positional information may be communicated to the sensor observation system  160  to assess whether to provide an alert signal to the user  115 . 
     In still other embodiments, the sensor system  120  (or the footpath presence sensor) may be or include a camera system  400  having a field of view  405  overlapping the footpath  110  as illustrated in  FIG. 4 . With reference to  FIG. 4 , the camera system  400  is capable of detecting the presence of the user  115  on the entry apron  140  of the footpath  110 , the exit apron  145  of the footpath  110 , and at any other portion of the footpath  110  as the user  115  is traveling within the footpath  110 . Upon detecting the user  115 , the camera system  400  may generate the footpath presence signal indicating that the user  115  is located on the footpath  110 . 
     In some embodiments, upon detecting the presence of the user  115 , the camera system  400  may capture one or more images of the user  115  to identify the user  115 . The identity of the user  115  may determine whether the sensor observation system  160  (described in further detail below) will generate the alert signal notifying the user  115  to hold the safety rail  105  as the user  115  travels along the footpath  110 . Such embodiments may be useful in multiple-person households, where only one or two people may be sufficiently young, infirm, or elderly to require assistance by the safety rail monitoring system  100 . 
     In such embodiments, after the camera system  400  obtains the images, the images may be processed via an image processor (not shown) that may be integrated with the camera system  400  or may be part of a remote system (such as a computer) that is in communication with the camera system  400 . The image processor processes the images and identifies the user  115  based on the captured images. The camera system  400  may include a database having stored images of all known household members. In such embodiments, the image processor may compare the captured images with the stored images in the database to identify the user  115 . Upon identifying the user  115 , the camera system  400  communicates the information (such as via the footpath presence signal) to the sensor observation system  160 . Based on the information, such as whether the user  115  has been identified as requiring the use or assistance of the safety rail monitoring system  100 , the sensor observation system  160  may or may not generate the alert signal to the user  115 . 
     Although the camera system  400  is illustrated in  FIG. 4  adjacent the entry apron  140  with a field of view  405  facing generally down the footpath  110 , the camera system  400  may include a second camera (not shown) near the exit apron  145  of the footpath  110  having a field of view facing generally up the footpath  110  to ensure that the camera system  400  adequately monitors the entire footpath  110 . 
     In other embodiments, the camera system  400  may instead be a radar system (not shown). Similar to the camera system  400 , the radar system may have a field of view overlapping the footpath  110  and comprise at least one of the following: micro-impulse radar, a physically scanned radar, a continuous wave radar, a pulsed radar, a moving target indicator radar, a pulse Doppler radar, a frequency modulated radar, or a phased array radar. The radar system detects movement of the human user  115  within the footpath  110  and obtains images of the user  115 . In a similar manner as described previously, the images may be compared to a stored database of images to identify the user  115 . 
     In some embodiments, the sensor system  120  may further detect whether the user  115  is moving along the footpath  110 , and may detect the speed and direction of movement of the user  115 . For example, with reference to  FIG. 1 , the footpath  110  may include a plurality of presence sensors  135  spaced along the footpath  110  as described previously. As the user  115  moves along the footpath  110 , the user  115  triggers subsequent sensors  135  along the footpath  110 , and based on the time that it takes the user  115  to trigger subsequent sensors  135 , the movement speed of the user  115  may be determined by the sensor system  120 . In such embodiments, the footpath presence signal generated by the sensors  135  includes an indication of whether the user  115  is in motion on the footpath  110  and the speed at which the user  115  is moving. In other embodiments, such as where the footpath presence sensors  135  include one or more light curtains  235 , the speed and/or the direction of motion of the user  115  along the footpath  110  may also be detected by monitoring the interruption of the light beams  245 . In still other embodiments, the speed and direction of motion of the user  115  may be determined by monitoring a real-time position of the tag  300  (such as via a global positioning system) or by the camera system  400 . In some embodiments, the sensor system  120  may detect the direction of travel of the user  115  on the footpath  110 . In such embodiments, safety rail monitoring system  100  may employ different settings or alert criteria based on the direction of travel (e.g., whether user  115  is traveling up or down a staircase). 
     As described previously, the sensor system  120  may include a second sensor subsystem  130  operatively coupled to the safety rail  105  and configured to detect at least one of a contact presence or contact absence between the human and the safety rail  105  and generate a safety rail contact signal. With reference to  FIG. 1 , the second sensor subsystem  130  may be coupled to or arranged along the safety rail  105  and may comprise one or more individual safety rail sensors  150 . Preferably, at least one safety rail sensor  150  is positioned on the safety rail  105  near or adjacent the entry apron  140  of the footpath  110  and at least one other safety rail sensor  150  near or adjacent the exit apron  145  of the footpath  110  to detect the user&#39;s  115  approach from either side of the footpath  110 . In such embodiments, the second sensor subsystem  130  may detect the user  115  as the user enters the footpath  110  near the entry apron  140  (e.g., the user begins walking down the staircase), and detects the user  115  at the exit apron  145  when leaving the footpath  110  (e.g., the user walks away from the staircase after reaching the lower level). 
     As mentioned previously, the second sensor subsystem  130  also includes a plurality of safety rail sensors  150  positioned along the safety rail  105  at various points along the footpath  110 . The safety rail sensors  150  may be arranged in a variety of configurations along the safety rail  105 . For example, in one embodiment, the footpath  110  may be a staircase and the safety rail  105  may include an individual safety rail sensor  150  coupled to the safety rail  105  next to each step in the staircase  110 . In other embodiments, a single safety rail sensor  150  may be used for multiple stairs to reduce the number of total sensors  150  needed to monitor the safety rail  105 . In still other embodiments, the sensors  150  may be arranged in a different configuration, such as distributed at specific distance intervals along the safety rail  105 . Collectively, these sensors  150  are configured to detect the presence or absence of contact from the user  115  on the safety rail  105 , and to generate the safety rail contact signal based on whether contact is detected. 
     In some embodiments, the sensors  150  may be configured to detect the user  115  when the user  115  is in proximity to (e.g., hand hovering near the safety rail  105 ), but not touching the safety rail  105 . In other words, the sensors  150  detect whether the user  115  is touching and/or holding on (or in close proximity) to the safety rail  105  as the user  115  walks along the footpath  110 . In other embodiments, the sensors  150  may be further be configured to detect a grip pressure exerted by the user  115  on the safety rail  105  to determine whether the user  115  is properly holding on to the safety rail  105 . In such embodiments, the sensors  150  may be able to distinguish between a mere touch or contact by the user  115  and a grip by the user  115  on the safety rail  105 . 
     Any one of a variety of sensors capable of detecting the presence or absence of the user&#39;s  115  contact with or proximity to the safety rail  105  may be suitable for use. For example, in some embodiments, the safety rail sensors  150  may include any of the following: optical sensors, acoustic sensors, infrared sensors, photocell sensors, ultrasonic sonar sensors, radar sensors, micro-impulse radar sensors, proximity sensors, pressure sensors/plates, weight sensors, microwave sensors, motion sensors, Doppler sensors, electrical resistivity sensors, capacitance sensors, or any other active or passive sensors. It should be understood that in some embodiments, the sensors  150  may not all be of the same kind or type of sensors. 
     In some embodiments, the footpath  110  may include more than one safety rail  105 . For example, with reference to  FIG. 1 , the footpath  110  may include a second safety rail  155  bordering an opposite side of the footpath  110  relative to the safety rail  105 . The second safety rail  155  may include a plurality of sensors  180  arranged in the same or similar manner as described previously with respect to the sensors  150  of the safety rail  105 . In such embodiments, the safety rail sensors  180  may be configured to determine whether the user  115  is contacting the second safety rail  155 . In such embodiments, the sensors  180  of the second safety rail  155  may be configured to convert a contact presence (or absence) by the user  115  and generate a second safety rail contact signal and indicate whether the user  115  is contacting the second safety rail  155 . If the sensor system  120  determines that the user is not contacting either of the safety rails  105 ,  155 , the sensor observation system  160  may generate an alert signal. 
     In other embodiments, the sensor system  120  may be further configured to determine whether the user  115  is simultaneously contacting both safety rails  105 ,  155 . In such embodiments, the safety rail  105  may be configured to generate the safety rail contact signal and the second safety rail  155  may be configured to generate a second safety rail contact signal. Based on both of the safety rail contact signals, the sensor observation system  160  may determine whether the user  115  is contacting both safety rails  105 ,  155  simultaneously and generate an alert signal if the user  115  is not contacting the safety rails  105 ,  155 . Further details regarding the sensor observation system  160  and the alert signal are described below. 
     In other embodiments, one or both safety rails  105 ,  155  may include or support both the footpath presence sensors  135  and the safety rail sensors  150 ,  180  to provide a fully integrated system for simple installation or retrofit. For example, as a person ages, the person may wish to install the safety rail monitoring system  100  in their home. By having both sets of sensors  150 ,  180  coupled to or supported by the safety rails  105 ,  150 , the person may need only install one or both of the safety rails  105 ,  150  to border a selected footpath  110 , such as a staircase. In other embodiments, the safety rail  105  may be a contact strip that is simply attached to or otherwise coupled with an existing handrail. 
     Although the first and second sensor subsystems  125 ,  130  of the sensor system  120  have been described as individual, standalone systems, these systems  120  may share various components and operate in a cooperative. For example, in one embodiment, both the first and second subsystems  125 ,  130  may initially be in a sleep mode. When the first sensor subsystem  125  detects the presence of the user  115  within its activation field, the first sensor subsystem  125  sends an activation or wake-up signal to activate the second sensor subsystem  130 . Once activated, the second sensor subsystem  130 , via the safety rail sensors  150 , determines whether the user  115  is holding on or contacting the safety rail  105 . 
     As mentioned previously, the sensor system  120  detects whether user  115  is present on the footpath  110  (via the footpath presence sensors  135 ) and whether the user  115  is contacting or touching the safety rail  105  (via the safety rail sensors  150 ). Upon detecting whether the user  115  is present on the footpath  110 , and detecting whether the user  115  is holding the safety rail  105 , the sensor system  120  generates a footpath presence signal with information about the user&#39;s presence on the footpath  110 , and a safety rail contact signal with information about whether the user  115  is contacting the safety rail  105 . These signals are received by the sensor observation system  160 , which is configured to generate an alert signal based on the footpath presence and safety rail contact signals indicating that the user  115  is concurrently present on the footpath  110  without contacting the safety rail  105 . Further details of the sensor observation system  160  are discussed below with particular reference to  FIGS. 1 and 5 . 
     As described previously, the sensor observation system  160  receives the signals from the sensor system  120  and if the user  115  is not holding the safety rail  105 , the sensor observation system  160  warns or alert signals the user  115  that the user  115  should grip or otherwise hold on to the safety rail  105  while walking along the footpath  110 . In some embodiments, the sensor observation system  160  will not generate an alert signal unless the footpath presence signals and/or the safety rail signals received from the sensor system  120  indicate that the user  115  is in motion on the footpath  110  without contacting the safety rail  105 . If the user  115  is not in motion (e.g., the user  115  walked up to the entry apron  140  but did not continue walking along the footpath  110 ), the sensor observation system  160  may not generate alert signal. 
     With reference to  FIG. 5 , the warning signal or alert signal generated by the sensor observation system  160  may be any suitable signal that warns the user  115  to hold the safety rail  105 . For example, the alert signal may be (a) an audible signal or tone, such as a buzzer, beep, or an alarm; (b) synthesized speech or a spoken message (e.g., a command to stop, a command to hold the safety rail, or any other command), or (c) any other signal heard by the user delivered through a speaker system  165 . The warning signal may additionally, or alternatively include, a visual signal perceived by the user  115 , such as a person walking (when it is safe to travel on the footpath  110 ) or a hand (when an object is present on the footpath  110 ), or any other signals, including signals commonly seen on pedestrian crosswalks. The visual signal may be presented to the user  115  on a display screen  170  and may include a textual message  175  and/or a graphic image warning the user  115  to stop and hold on to the stair rail  105  before continuing to walk along the footpath  110 . 
     In some embodiments, the speaker system  165  and/or the display screen  170  may mounted near the entry apron  140  of the pathway  110  (e.g., on a top or beginning step of the staircase) for easy reference or viewing by the user  115 . Since injury may be more likely and/or more severe if one were to fall going down the stairs rather than fall while walking up the stairs, it is preferable that the sensor observation system  160  (and in particular the display screen  170  and/or speaker  165 ) is positioned near the entry apron  140  of the staircase  110 . In other embodiments, the sensor observation system  160  may be positioned both at the entry apron  140  and the exit apron  145  (e.g., the bottom step) of the footpath  110 . In still other embodiments, the speaker  165  and the display screen  170  may be positioned at other points along the footpath  110  so that the sensor observation system  160  may still effectively warn the user  115  to hold the safety rail  105  at any point along the footpath  110 . 
     In other embodiments, the visual signal may simply be a visible light source that alert signals the user  115  to hold on to the safety rail  105 . With reference to  FIG. 6 , a light-emitting diode (LED)  605  or other light source may be mounted adjacent both the entry apron  140  and the exit apron  145  of the footpath  110  (and at various other positions along the footpath  110 ). When the user  115  is contacting the safety rail  105  with an appropriate grip force that the sensor system  120  determines to be sufficient for supporting the user  115 , the LED  605  may be green, indicating that the user  115  may continue along the footpath  110 . If, on the other hand, the user  115  is not contacting the safety rail  105 , or is not exerting sufficient grip force on the safety rail  105 , the LED  605  may be red to warn the user  115  to touch and hold the safety rail  105  before continuing on the footpath  110 . 
     In some embodiments, the safety rail monitoring system  100  may include an output device (not shown), such as a small radio, a mobile phone, or other electronic device, that is carried or worn by the user  115  and is in wireless communication with the sensor observation system  160 . In such embodiments, the audible signal may be communicated from the sensor observation system  160  through the output device so that the user  115  can hear the signal. In some instances, the warning signal may include a vibratory signal where the output device (e.g., a mobile phone) vibrates so that the user  115  can feel it and remember to hold on to the safety rail  105 . 
     In other embodiments, the output device may include a phone, computer, or other device worn or carried by a caregiver tasked with caring for the user  115 . The alert signal may be transmitted to the output device to alert the caregiver that the user  115  is on the footpath  110  and not contacting the safety rail(s)  105 ,  155 . The caregiver may thereafter approach the footpath  110  to ensure that the user  115  is safe and holding the safety rail(s)  105 ,  155 . 
     In some embodiments, the safety rail monitoring system  100  may be in communication with an external device (not shown), such as a computer or other database. The safety rail monitoring system  100  may be further configured to transmit a progress signal to the external device to track statistics for the user&#39;s  115  regarding a number of times the user  115  travels along the footpath  110  and the propensity of the user  115  to contact and hold the safety rail(s)  105 ,  155 . The progress signal may be one or a combination of: the footpath presence signal, the safety rail contact signal, the alert signal, or a different signal. With this information, the user  115 , the user&#39;s  115  family, or a caregiver may track the user&#39;s  115  progress and determine a corrective course of action for the user&#39;s  115  safety if needed. For example, if the user  115  is not consistently holding on to safety rail(s)  105 ,  155  as the user  115  traverses the footpath  110 , then the caregiver or family members may discuss this with the user  115  and take additional steps to ensure the user&#39;s  115  safety (such as by implementing a barrier  700  discussed in further detail below with reference to  FIG. 7 ). 
     In some embodiments, the alert signal generated by the sensor observation system  160  may be based on a time duration for which the footpath presence signal and the safety rail contact signal(s) indicate that the human is concurrently present on the footpath  110  without making contact with one or both of the safety rails  105 ,  155 . For example, if the sensor system  120  detects the user  115  within the footpath  110  for a predetermined amount of time (for example, five seconds, ten seconds, fifteen seconds, or any other suitable time period) without the user  115  making contact with one or both of the safety rails  105 ,  155 , then the sensor system  120  may generate the footpath presence signal and the safety rail contact signal and transmit the signals to the sensor observation system  160  to generate the alert signal. If the user  115  is present within the footpath  110  and contacts the safety rail(s)  105 ,  155  within the predetermined amount of time, then no alert signal is generated. For example, the sensor observation system may permit user  115  to have short periods of no-or-poor safety rail contact as long as adequate contact is resumed within a specified time period. 
     In other embodiments, the alert signal generated by the sensor observation system  160  may be based on a travel distance and/or a travel direction of the user  115  (such as measured from the entry apron  140  or the exit apron  145  of the footpath  110 ) for which the footpath presence signal and the safety rail contact signal indicate that the user  115  is concurrently present on the footpath  110  without making contact with the safety rail(s)  105 ,  155 . As mentioned previously, the sensor system  120  is configured to determine a location of the user  115  on the footpath  110 . In such embodiments, the sensor system  120  may further generate a user presence location signal to indicate a location of the user  115  on the footpath  110 , and transmit the user presence location signal to the sensor observation system  160 . In some embodiments, the safety rail sensors  150  may be further configured to detect a location of the contact between user and the safety rail(s)  105 ,  155  and generate a safety rail contact location signal indicating a position along the safety rail(s)  105 ,  155  at which the user  115  is making contact. 
     Based on one or both of the user presence location signal and the safety rail contact location signal, the sensor system  120  (or the observation system  160  or other system of the safety rail monitoring system  100 ) may determine whether the user  115  has crossed a threshold distance relative to the entry or exit aprons  140 ,  145  after which the sensor observation system  160  generates the alert signal if the footpath presence signal and the safety rail contact signal(s) indicate that the user  115  is not contacting the safety rails  105 ,  155 . In some embodiments, the sensor observation system  160  may generate the alert signal based on one or both of the travel distance and the travel direction of the user  115  on the footpath  110  (e.g., whether the user  115  is walking up or down the staircase  110 ). 
     In other embodiments, the alert signal may be provided at a location on the footpath  110  based on the user presence location signal to optimize the likelihood that the user  115  will hear or see the alert signal as the user moves along the footpath  110 . For example, as described previously, a plurality of electronic or other devices (e.g., speakers, displays, illumination sources, etc.) may be distributed along the footpath  110 . In such embodiments, the alert signal may be delivered to the closest device relative to the user  115  based on a location of the user as determined by the user presence location signal. 
     In other embodiments, the sensor system  120  may be configured to distinguish between multiple users  115  on the footpath  110  and determine whether some or all of the users  115  are contacting the safety rail  105 . For example, the sensor system  120  may be configured to determine a location for each of the multiple users  115  on the footpath  110  and a location of one or more distinct contact points on the safety rail  105  corresponding to each user  115 . The sensor system  120  may be configured to generate the user presence location signal indicating a location of each user  115  on the footpath  110 , and a safety rail contact location signal indicating a location of one or more distinct contact points on the safety rail  105  by the users  115 . The sensor observation system  160  (or other system of the safety rail monitoring system  100 ) receives the user presence location signal and the safety rail contact location signal and determines the number and location of users  115  present on the footpath  110  and the number and location of distinct contact points on the safety rail  105 . The sensor observation system  160  thereafter determines whether the location of each of the users  115  matches a corresponding location for a detected contact point on the safety rail  105 . If all the users  115  are contacting the safety rail  105 , the number of detected users  115  will be equal to the number of detected distinct contact points on the safety rail  105 , with the location of each contact point on the safety rail  105  matching a corresponding location of an individual user  115  on the footpath  110 . If the number of detected users  115  on the footpath  110  exceeds the number of detected contact points on the safety rail  105 , then the sensor observation system  160  generates an alert signal indicating that one or more users  115  is not contacting the safety rail  105 . Additional details regarding the sensor observation system  160  and the alert signals are described below in further detail. 
     In another embodiment, in addition to warning the user  115  to hold on to the safety rail  105 , the safety rail monitoring system  100  or the sensor observation system  160  may further be configured to prevent the user  115  from traveling on the footpath  110  without making contact with the safety rail  105 . For example, with reference to  FIG. 7 , the safety rail monitoring system  100  may further include a barrier system  750  having a barrier  700  positioned proximal to the entry apron  140  (or exit apron  145 ) to impede the progress of the user  115  on the footpath  110 . The barrier  700  may be configured to move only when the footpath presence signal indicates that the user  115  is present on the footpath  110 . In some embodiments, the barrier  700  may be a boom barrier or other physical structure that blocks the footpath  110  and locks in position upon the sensor observation system  160  receiving the footpath presence signal and the safety rail contact signals that indicate that the user  115  is present on the footpath  110  without making contact with the safety rail  105 . Once the user  115  contacts the safety rail  105 , the barrier  700  may move out of position to allow the user  115  to move along the footpath  110 . 
     In some embodiments, the barrier  700  may be self-propelled and move along a track  705  extending next to the footpath  110  and the safety rail  105 . The barrier  700  may include one or more wheels (not shown) that engage the track  705  and a prime mover configured to drive the one or more wheels along the track  705  via a chain drive, a gear drive, an adhesion drive, or other suitable drive systems (not shown). As mentioned previously, the sensor system  120  (e.g., the footpath sensors  135 ) is configured to determine a movement speed of the user  115  along the pathway  110 . In such embodiments, the sensor system  120  may communicate the speed and movement information of the user  115  to the barrier system  750  via the footpath presence signal (or via a different signal). With this speed and movement information, the barrier system  750  determines an appropriate movement speed (which may be approximately equal to the movement pace/speed of the user  115  or may be approximately 5-10% or more faster), at which to move the barrier  700  along or next to the safety rail  105  on the track  705 . As long as the user  115  maintains contact with the safety rail  105 , the barrier  700  continues moving on the track  705  until reaching the exit apron  145 , at which point, the barrier  700  pivots out of position to allow the user  115  to exit the footpath  110 . If the user  115  releases the safety rail  105  or fails to exert an adequate grip force thereon while moving through the footpath  110 , the barrier  700  may stop, such as via a brake system (not shown) that engages one or more of the wheels, and the sensor observation system  160  may alert or warn the user  115  to hold the safety rail  105 . The barrier  700  may remain stopped until the user  115  contacts the safety rail  105 . 
     In some embodiments, the brake system may also serve to adjust or regulate the movement speed of the mobile barrier  700  to the match the user&#39;s  115  real-time movement speed. For example, if the user  115  speeds up or stops while moving on the footpath  110 , the barrier  700  may also speed up or stop moving so as to maintain a desired distance and position in advance of the user  115 . 
     The sensor system  120  may further include barrier sensors  740  mounted on the barrier  700  and configured to monitor a distance or separation between the user  115  and the barrier  700  as the user  115  walks along the footpath  110 . The barrier sensors  740  help ensure that the movement speed of the mobile barrier  700  is controlled to maintain a distance or separation from the user  115  within a specified range. For example, in some embodiments, the barrier  700  may be moved at a measured speed so as to maintain a separation from the user  115  of between 0 and 12 inches. In other embodiments, the separation may be maintained at between 12 inches and 24 inches. 
     The barrier sensors  740  may include sensors configured to detect a force or contact on the barrier  700  to determine whether the user  115  is falling or has fallen onto the barrier  700 . For example, the barrier sensors  740  may determine that a fall event has occurred by sensing or measuring a contact force between the user  115  and the mobile barrier  700  and comparing the measured contact force to a threshold value. The threshold value can be determined for individual users  115  (such as based on a user&#39;s  115  weight), and is preferably set at a sufficiently high contact force so that the barrier sensors  740  can distinguish between a light touch on the barrier  700  (such as when the user  115  merely has a hand on the barrier  700  for balance) and a heavy force (such as when the user  115  is leaning onto or has fallen onto the barrier  700 ). The barrier system  750  may further include an arrestor lock (not shown) that engages with the track  705  to lock the mobile barrier  700  in position, such as when the sensor system  120  (or barrier sensors  740 ) detects a fall event by the user  115 . 
     In some embodiments, the barrier  700  may be propelled by force applied by the user  115 . For example, the barrier  700  may move in response to the user  115  grasping the barrier  700  and pushing the barrier  700  as the user  115  walks along the footpath  110 . In such embodiments, the barrier sensors  740  may determine whether the user  115  is grasping the barrier  700 . As long as the user continues grasping the barrier  700 , the barrier  700  may be moved along the footpath  110 . If the user  115  releases the barrier  700 , the barrier  700  may automatically lock in position until the user  115  again grasps the barrier  700  and continues moving. In some embodiments, the barrier  700  may further include a manually actuatable lock that the user  115  may press to release the lock and allow the barrier  700  to be pushed again along the footpath  110 . In other embodiments, the lock may also be actuatable to manually lock the barrier  700  in position at any point along the footpath  110 . 
     In some embodiments, once the barrier  700  has reached the exit apron  145 , the barrier  700  may remain at that position until the user  115  once again walks on the footpath  110 , at which point the barrier  700  will move from the exit apron  145  toward the entry apron  140  ahead of the user  115 . In other embodiments, the barrier  700  may automatically return to the entry apron  140  after reaching the exit apron  145  and allowing the user  115  to exit the footpath  110 . For example, the barrier  700  may move only after a predetermined amount of time has elapsed to allow the user  115  to clear the footpath  110 . In still other embodiments, the barrier system  750  may include a call button  710  positioned next to one or both the entry apron  140  and the exit apron  145  so that the barrier  700  may be called from its position toward the user  115 . For example, in embodiments where multiple users may be using the safety rail monitoring system  100 , if a first user walks down the footpath (e.g., the staircase of  FIG. 7 ), the barrier  700  remains at the exit apron  145 . If a second user approaches the entry apron  140 , the second user may press the call button  710  to return the barrier  700  back up the stairs to support the second user. In still other embodiments, the sensor system  120  may sense the user  115  near the entry apron  140  or the exit apron  145  of the footpath  110  and automatically move the barrier  700  to the user&#39;s position. 
     In some embodiments, the barrier system  750  may include a second mobile barrier  730  that is extendable to cross the travel route along the footpath  110  and configured to move along the track  705  behind the user  115  at substantially the movement speed of the mobile barrier  700  to provide a protective enclosure around the user  115  and help prevent the user  115  from falling backward (e.g., from falling down the staircase). In some embodiments, the mobile barrier system  750  may include a seat  735  between the barriers  700 ,  730  to allow a user  115  to sit down while the mobile barrier system  750  carries the user  115  along the travel route of the footpath  110 . 
     In some embodiments, the mobile barrier  700  may include a payload container  760 , such as a basket, tray, sack, or other container for carrying the user&#39;s  115  personal accessories or portable items, such as groceries, books, food and beverages, laundry, a cane, mail, parcels or packages, or other suitable items so that the user  115  can have his or her hands free to hold on to the safety rail(s)  105 ,  155  while traversing the footpath  110 . In some embodiments, the payload container  760  includes sidewalls  765 , a bottom  770 , and an open top  775  that defines an interior region for holding the items. The sidewalls  765  may be made from a flexible, such as cloth or other flexible material, or may be rigid. The payload container  760  may be removable from the mobile barrier  700  to allow the user  700  to remove the payload container  760  when not needed, or the payload container  760  may be integrated into the barrier  700 . 
     As mentioned previously, in some embodiments, the footpath  110  may include two safety rails  105 ,  155 . In such embodiments, the barrier  700  may extend across the footpath  110  from the safety rail  105  to engage the second safety rail  155 . The mobile barrier system  750  may be further configured prevent the user  115  from traveling on the footpath  110  without the user  115  making contact with at least one of the safety rails  105 ,  155  or the mobile barrier  700 . For example, if the user  115  approaches the footpath  110  and holds on to the second safety rail  155 , the mobile barrier  700  may move along the track  705  at a speed substantially matching the movement speed of the user  115 . Similarly, if the user  115  approaches the footpath  110  and contacts the barrier  700 , the barrier  700  may move along the track  705 . 
     In some embodiments, the safety rail monitoring system  100  may include an input system (not shown) configured to receive input or programming instructions from one or more users to program or control various parameters of the safety rail monitoring system  100 . For example, the input system may be used to activate or deactivate any of the sensors of the sensor system  120 , the barrier  700 , or any other components of the monitoring system  100 , as desired. In other embodiments, the input system may be used to program various aspects of the AIDC system, including the tag  300  and the tag reader  305 , such as identifying the number of users carrying a tag, assigning unique identification frequencies for each of the users so the system  100  can distinguish between the users, and/or defining the interrogatory zone of the tag reader. 
     The input system may also be used to allow the users to program the monitoring system  100  to best serve the needs of the various users, such as in a multiple-user household. The input system may receive user information, such as height, weight, age, or other parameters that may be used by the various sensors of the system  100  to identify the users while on the footpath  110 . In some cases, certain users may not need to hold on to the safety rails  105 ,  155  or use the barrier  700 , such as for younger users in good physical condition. For those users, the input system may be used to program the monitoring system  100  to ignore when those users are in the footpath  110  or to automatically move the barrier  700  out of position to allow the user free access to the footpath  110 . As those users age, or if they suffer an injury or otherwise need the monitoring system  100  in the future, the input system may be used to reactivate those users as needed. In other embodiments, the input system may be used to control other features of the monitoring system  100 . 
       FIG. 8  is a block diagram illustrating a method for monitoring use by a human of a safety rail with a mobile barrier bordering a footpath. It should be understood that the method described below is for illustration purposes and the order in which the steps are described is not meant to be limiting. It should be understood that in other embodiments, the steps may occur in a different order. 
     With particular reference to  FIG. 8 , at step  802 , the footpath presence sensor detects a presence and a movement speed and movement direction of the user along the footpath. In some embodiments, the presence of the user and the movement speed and direction may also be determined by communication of the footpath presence sensor with an electronic device (such as a mobile phone) having a position determination system (e.g., GPS), where the electronic device is carried or worn by the user. At step  804 , the footpath presence sensor generates a footpath presence signal in response to detecting the presence of the user in the footpath, where the footpath presence signal indicates the movement speed of the user on the footpath. 
     At step  806 , the safety rail sensor detects a contact presence or contact absence of a contact between the user and the safety rail. In other words, the safety rail sensors detect whether the user is holding on to the safety rail. As mentioned previously, in some embodiments, the safety rail sensors may also determine a grip pressure that the user is exerting on the safety rail to determine whether the user has an adequate grip on the safety rail. Thereafter, at step  808 , the safety rail sensor generates a safety rail contact signal in response to the detected contact presence or absence on the safety rail. 
     At step  810 , the barrier system or other system of safety rail monitoring system determines whether the user is making contact with the safety rail while moving on the footpath. At step  812 , if the footpath presence signal and safety rail contact signal indicate that the user is moving on the footpath while making contact with the safety rail, the self-propelled mobile barrier extending across the travel route along the safety rail may be moved at substantially the movement speed of the user in advance of the user. In some embodiments, the barrier may include a payload container to carry the user&#39;s belongings as the user moves along the footpath to allow the user to hold the safety rails while moving on the footpath. 
     At step  814 , if the user releases contact with the safety rail while walking along the footpath, the mobile barrier may lock in position until the user again contacts the safety rail. In some embodiments, at step  816 , the sensor observation system may also generate a warning or alert signal communicating to the user that the user must hold on to the safety rail before continuing along the footpath. As mentioned previously, the alert signal may be an audible signal or tone, such as synthesized speech (e.g., a command to stop or to hold the safety rail) or a buzzer, or the alert signal may be a visual signal, such as a graphic image, text, or visible light. When the user receives the alert signal, the user may thereafter contact and hold the safety rail to continue walking along the footpath without receiving further warnings and allowing the barrier to move ahead of the user. 
     Other embodiments are possible. Although the description above contains much specificity, these details should not be construed as limiting the scope of the invention, but as merely providing illustrations of some embodiments of the invention. It should be understood that subject matter disclosed in one portion herein can be combined with the subject matter of one or more of other portions herein as long as such combinations are not mutually exclusive or inoperable. 
     The terms and descriptions used above are set forth by way of illustration only and are not meant as limitations. Those skilled in the art will recognize that many variations can be made to the details of the above-described embodiments without departing from the underlying principles of the invention.