Low Level Function
5.13.10 Display Current Road Information to Driver

Overview

This Function shall be capable of providing the following facilities:

(1) The ability to receive both the current recommended speeds and headways and the legal speed limits for display to the Driver of the Host Vehicle.
(2) A HMI that shall be able to display both speed limits, except when either there is no recommended speed limit, or it is greater than the legal speed limit.
(3) If there is no recommended speed limit, or it is greater that the legal speed limit, the HMI shall have the ability to display the legal speed limit with a warning that there is no recommended speed limit.
(4) If the speed of the Host Vehicle exceeds either the recommended speed or the legal speed limit, then the HMI shall display a warning message to the Driver.
(5) The HMI shall only display the headway with the recommended speed limit.
(6) When any changes are made to the recommended speed and headway, the HMI shall be able to provide an indication of the reason for the change.
(7) The HMI shall also have the ability to display a warning when the Host Vehicle is being driven in an unsafe manor, i.e. poor safety behaviour due to excessive speed, or maintaining less than the minimum headway.
(8) The HMI shall be able to continuously update the display to provide the Driver with the speed and headway for the Host Vehicle's current and expected locations within the road network and to show or remove any unsafe driving warnings.
(9) If for any reason the HMI does not receive any inputs, it shall have the ability to show a "system not working" indication.

Functional Requirements

(a) continuously monitor for receipt of any of the input data flows
(b) whenever the road information for display data flow is received in (a), display its contents including the legal speed limit and the part of the road network (inter-urban or urban) that the host vehicle is using to the driver through the HMI using the current road information data flow
(c) whenever the current recommended speed and headway data flow is received in (a), display its contents (including the reasons for changes) to the driver through the HMI using the current speed limits and headways output data flow
(d) in (c) continue to display the recommended speed limit provided that it is less than the legal speed limit for the current and expected next road segments
(e) if no recommended speed limit is received in (a), then only display the current legal speed limit received in (b) and output to the driver through the HMI with it an advisory message saying that there is no recommended speed limit
(f) if the recommended speed limit received in (c) exceeds the legal speed limit received in (b) then only display the legal speed limit and output to the driver through the HMI an advisory message saying that there is no recommended speed limit
(g) if no recommended or legal speed limits are received in (b) or (c) then output a message to the driver through the HMI in the current speed limit data flow saying the speed limit service is unavailable
(h) when the roadside speed indication details data flow is received in (a) check the speed value it contains against the current legal and recommended speed limits that have been received in (b) and (c)
(i) if a difference is found in (h), provide a warning of this to the driver in the possible speed indication error data flow and also send the data from which the same warning message can be produced to either the function (in the inter-urban speed being exceeded) or Output Lane & Speed Commands to Urban Roads function (in the urban speed being exceeded) depending on whether the vehicle is in the inter-urban or urban part of the road network
(j) continue to send the output in (i) for as long as the difference persists and stop output of the possible speed indication error data flow when it does not
(k) the output of the possible speed indication error data flow should only be made if a recommended or legal speed limit has been received in (b) or (c), i.e. the output must not be sent if there is no data with which to make a comparison
(l) when the vehicle speed data flow is received in (a), check it against the legal speed limit received in (b) and the recommended speed received in (c) and display a warning to the driver if either is being exceeded by the vehicle in the recommended speed or legal speed limit exceeded data flow
(m) if either of the data flows in (l) is sent then determine in which part of the road network (inter-urban or urban) the vehicle is located and send whichever is appropriate of the inter-urban speed being exceeded or urban speed being exceeded data flows to the Output Lane & Speed Commands to Inter-urban Roads or Output Lane & Speed Commands to Urban Roads functions respectively
(n) the output of all speed limit information must be made in a standard way
(o) whenever the fused road and traffic conditions data flow is received in (a), display its contents to the driver through the HMI using the current road and traffic conditions data flow
(p) whenever the safety behaviour status for display data flow is received in (a), display the warning that it contains through the HMI using the safety behaviour warning data flow, for as long as the warning is received, it being removed when it ceases to be present
(q) if none of the data flows is received in (a) for a period of time, the display shall show a "system not working" indication.

Diagrams

The Diagram(s) is (are) the diagram(s) where you can find the function :
  • DFD 5.13 Provide Vehicle Data and ISA
  • Functional Tree of Area 5

    • Parent Higher Level Function

    Input logical dataflows

    Output logical dataflows

    User needs

    Number

    Description

    7.4.1.48
    Hazardous Location Notification - The system shall provide "copies" of the traffic signs that are relevant to the current section of the road (e.g. speed limit, road hazards, junctions) to the driver at all times via an in-vehicle display.
    7.4.2.5
    The system shall provide "copies" of the traffic signs that are relevant to the current section of the road (e.g. speed limit, road hazards, junctions) to the driver at all times via an in-vehicle display.
    7.4.3.9
    The system shall provide "copies" of the traffic signs that are relevant to the current section of the road (e.g. speed limit, road hazards, junctions) to the driver at all times via an in-vehicle display.
    7.4.4.1
    The system shall be able to recommend a safe speed limit according to the prevailing traffic, weather and road conditions based on the current legal speed limit.
    7.4.4.11
    The system shall be able to compare the reported speed of a vehicle with the current speed limit and send a warning to that vehicle for display to the driver, via an in-vehicle device, that its current speed is greater than the legal speed limit.
    7.4.4.12
    The system shall be able to compare the reported speed of a vehicle with the current legal speed limit and display a warning to the driver, via a road-side device, if its current speed is greater than the legal speed limit.
    7.4.4.13
    The system shall be able to compare the reported speed of a vehicle with the current recommended speed limit and send a warning to that vehicle for display to the driver, via an in-vehicle device, if its current speed is greater than the recommended speed limit.
    7.4.4.14
    The system shall be able to compare the reported speed of a vehicle with the current recommended speed limit and display a warning to the driver, via a road-side device, if its current speed is greater than the recommended speed limit.
    7.4.4.15
    The system shall be able to warn the driver, via an in-vehicle device, that the host vehicle is exceeding the maximum speed limit.
    7.4.4.16
    The system shall inform the driver, via an in-vehicle display, that there is a modification to the speed limit ahead, and the reason for it.
    7.4.4.17
    The system shall provide "copies" of the traffic signs that are relevant to the current section of the road (e.g. speed limit, road hazards, junctions) to the driver at all times via an in-vehicle display.
    7.4.4.2
    The system shall be able to warn drivers, via an in-vehicle display, of different legal speed limits as a result of particular weather conditions.
    7.4.4.3
    The system shall provide legal speed limits continuously to the driver via an in-vehicle display according to the type of the host vehicle and the lane in which it is travelling (Intelligent Speed Adaptation - ISA).  A suitable message should be provided if the service provision cannot be guaranteed.
    7.4.4.4
    The system shall provide recommended speed limits continuously to the driver via an in-vehicle display according to the type of the host vehicle and the lane in which it is travelling (Intelligent Speed Adaptation - ISA).  A suitable message should be provided if the service provision cannot be guaranteed.
    7.4.4.7
    The system shall enable the driver of the host vehicle, via an in-vehicle device, to receive safety-related information (e.g. legal speed limit, recommended speed limit) from the TCC.
    7.4.5.2
    The system shall provide the current minimum headway for the current speed limit to the driver via an in-vehicle device.
    7.4.5.3
    The system shall be able to recommend a safe minimum headway according to the current speed limit, traffic, weather and road conditions to the driver via an in-vehicle device.
    7.4.5.4
    The system shall inform the driver, via an in-vehicle display, that there is a modification to the recommended headway ahead, and the reason for it.
    7.4.5.5
    The system shall be able to warn the driver, via an in-vehicle device, that the host vehicle is violating the minimum headway.
    7.4.6.15
    The system shall be able to advise the driver, via an in-vehicle device, of a recommended speed and distance from the vehicle ahead, based on the speed and characteristics (e.g. mass, load being carried) of the host vehicle and of the vehicle ahead.
    7.5.1.16
    The system shall be able to calculate an optimal speed for each type of vehicle through designated  sections of the road network and provide that information to drivers via an in-vehicle device.
    8.2.5.4
    The system shall be able to display continuously to the driver the current mandatory speed limit.