Low Level Function
3.1.1.5.18 Manage Urban Traffic Speeds and Headways

Overview

This Function shall be capable of providing the following facilities:

(1) The ability to provide the management of vehicle speed and headway settings within the urban road network.
(2) The ability to receive commands to implement legal speed settings, plus both suggested speed and headway settings from either the functionality providing the Road Network Operator interface, or the urban traffic management functionality, or as part of an incident, demand management, or environmental strategy.
(3) The ability to ensure that requests from the functionality providing the Road Network Operator interface take priority and override those from the urban traffic management functionality, but not those that are part of an incident, demand management, or environmental strategy.
(4) The ability to send speed and headway settings to the functionality that is responsible for the output of messages to Drivers of vehicles using the urban road network, both at the roadside and in the Vehicle, as well as to other functionality from which it can be sent to other parts of the system, to the Broadcaster entity.
(5) The ability to send the legal speed settings to the digital map data provider entity in case it needs to be used in future digital map updates.

Functional Requirements

(a) continuously monitor for receipt of the input data flows
(b) when the urban road legal speeds data flow is received in (a) store its contents locally for future use
(c) as a result of (b) send the new urban speed limits in the urban legal speed limits data flow to the Provide Support for Host Vehicle Systems functionality
(d) when either the urban speed and headway settings or the operator urban speed override data flows are received in (a) implement the speed that they contain by sending the new speed limit in the urban speed limit changes and updated urban speed limits data flows
(e) in (d) the speed limit in the operator urban speed override shall take precedence over the value in the urban speed setting data flow, except where this is provided as part of an incident, demand or environmental management strategy
(f) as a result of (d) and (e) also send the new speed limit and headway to the Provide Support for Host Vehicle Systems functionality in the urban suggested speeds and headways data flow and to the Output Lane & Speed Commands to Urban Roads function in the urban speed l&s commands data flow.

Diagrams

The Diagram(s) is (are) the diagram(s) where you can find the function :
  • DFD 3.1.1.5 Provide Urban Traffic Management Faciliti
  • Functional tree 3.1

    • Parent Higher Level Function

    Input logical dataflows

    Output logical dataflows

    User needs

    Number

    Description

    7.1.0.10
    The system shall be able to manage traffic in all or part of the road network using a methodology that is appropriate for urban roads, e.g. using traffic lights at junctions and with the possibility of incorporating facilities for pedestrians to cross the road in a controlled manner.
    7.1.7.1
    The system shall be able to show the maximum authorised speed of vehicles on selected carriageways to be shown to drivers.
    7.1.7.2
    The system shall be able to set variable speed limits on parts of the road network.
    7.1.7.3
    The system shall be able to calculate recommended speed limits for given traffic and weather conditions, and road network characteristics.
    7.1.7.5
    The system shall be able to support a database of all speed limits on the road network.
    7.1.7.6
    The system shall be able to support an in-vehicle database of road network data (e.g. speed limits, road hazards, junctions etc.).
    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.
    7.4.4.6
    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 a road-side device.
    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.
    7.4.4.8
    The system shall be able provide recommended speed limits from outside the vehicle, and to confirm that they are consistent with the limits that have been sent directly to that vehicle.
    7.4.5.1
    The system shall enable the TCC to calculate recommended headways for the current traffic and environment conditions.
    7.4.8.9
    The system shall enable the driver of the host vehicle to be advised, via an in-vehicle device, not to enter a zone defined by virtual cones.
    7.5.1.25
    The system shall enable the TCC to recommend the use of alternative routes for different types of vehicle.
    7.5.1.26
    The system shall enable the TCC to command the use of alternative routes for different types of vehicle.