## 5 Use Cases
### Route Assistant for Travelers with Special Needs  
This second case of the system is a route assistant for blind people. This assistant uses the data provided by the positioning system and open-door sensors. Using these data, this system improves the accessibility and safety for this type of passenger while traveling on the bus. Next, the principles of the operation of the route assistant are described. The passenger with special needs, who is a blind person in this case, waits for the bus to arrive at the stop. From the information system of the company, the passenger knows the expected arrival time of the bus that makes the journey required by the passenger, the location of the stop where they must board the vehicle, and the identifier of the line to take. When the vehicle is preparing to stop, the data connection between the mobile device of the traveler and the OBC of the vehicle is established using the Wi-Fi infrastructure. Once the connection with the OBC is established, a route-assistant service thread (STHi) is created and is dedicated to providing the data to the client application assistant (ACli) that runs on the mobile device of the traveler. At this point, the data packet exchange between the STHi thread and the ACli application begins, using the protocol described in Section 4. Next, the data used by the service, including how they are obtained and their treatment, are described:  
* User Profile--This datum indicates the type of traveler that is using the application; in this case, the traveler is a blind person. This datum is stored by the ACli application and sent to the STHi thread. * Details of the trip the traveler wishes to make, which consists of the line identifier (PLI), the origin stop (POS) and the destination stop (PDS)-These data are transmitted to the STHi thread by the ACli application. * Current vehicle position--This information consists of the geographical coordinates of the vehicle (VPO), the velocity (VSL) and the time point (VTI) in which the position was acquired. These data are provided by the infrastructure of the vehicle (positioning system), transmitted by the OBC, received by the CTH thread and stored in the shared memory for transmission to the ACli application by the STHi thread. * Line (VLI)--This datum indicates the programmed bus route provided by the infrastructure of the vehicle (control system operations), which the OBC transmits and the CTH thread receives and stores in the shared memory for the STHi thread to transmit to the ACli application. The infrastructure also provides the number of stops of the route (VNS). * Current Stop (VCS)--This datum indicates at which stop the vehicle is located if it is paused at a stop or the last stop it passed, if it is not at a standstill. This information is provided by the infrastructure of the vehicle (control system operations), which the OBC transmits and the CTH thread receives and stores in the shared memory for transmission by the STHi thread to the ACli application. The position of the current stop is also provided by the infrastructure (VIS). * Next stop along the route (VNS)--This datum indicates the next route stop and the estimated time of arrival (VTS). This datum is provided by the infrastructure of the vehicle (control system operations), transmitted by the OBC, received by the CTH thread and stored in the shared memory for transmission to the ACli application by the STHi thread. * State of vehicle doors (VDS)--This datum indicates whether the passenger access doors of the vehicle are open or closed. This information is provided by the infrastructure of the vehicle(vehicle door sensors), transmitted by the OBC transmits, received by the CTH thread and stored in the shared memory for transmission to the ACli application by the STHi thread. With these data, the route assistant can help a blind person to safely and comfortably complete a journey. For these travelers, the assistance is rendered by audio prompts, which are played on the mobile device of the traveler.