Low Level Function
3.1.1.5.22 Output s&g Commands to Urban Roads

Overview

This Function shall be capable of providing the following facilities:

(1) The provision of conventional "traffic light" type outputs to Drivers, Cyclists and Pedestrians using the urban road network.
(2) The ability to send the "traffic light" type outputs directly to Vehicles for output to Drivers using in-Vehicle devices.
(3) The ability to change the duration and sequence of the outputs according to data received from the following inputs:
       (a) Vehicle presence data from local Traffic via its own sensors;
       (b) Commands from the Implement Urban Traffic Commands Function;
       (c) Requests for local priority from Emergency Services (Centres and Vehicles), Public Transport Vehicles and Other Vehicles.
(4)  The assignment of priority of response to these inputs depending on their presence and when more than one is present, what the input from the Traffic Command Function allows.
(5)  The ability to respond to any of the above inputs according to the priority assignment, until the input that is being given priority is no longer present, in which case the Function shall implement the next highest priority input to produce the outputs.
(6)  The ability to use its own internal timings when none of the inputs identified above are available.
(7)  The ability to temporarily implement changes in the sequence of the outputs to accommodate "green wave" requests and to revert to using the highest priority inputs once the request has been fulfilled.
(8)  The ability to respond with an indication of whether or not a local priority request received from an Other Vehicle will be fulfilled and to fulfil priority requests from Other Vehicles based on the order in which they have been received, providing "failure" responses to those that have not been fulfilled.
(9)  The ability to provide an indication of the recommended speed profile for the Other Vehicle to arrive at the junction when the signal is green, based on data provided in its request for local priority.
(10)  The ability to give Emergency Vehicles the highest priority, followed by Public Transport Vehicles and lastly Other Vehicles when more that one local priority request is received.
(11)  The ability of the Road Network Operator to vary the order of priority in which requests are fulfilled whether they come from the same or different types of Vehicles.
(12) The ability to send information about local priority requests that it has received to adjacent down stream instances of its functionality.
(13) The ability to receive information about local priority requests from functionality located upstream of itself and to prepare for the arrival of the Vehicle, by temporarily adjusting its operating sequence so that it can be given priority at the most appropriate time so as not to impede the Vehicle's progress.
(14) The ability to respond to local inputs from Pedestrians if and when it is permitted within the sequence of outputs required by the Implement Urban Traffic Commands Function.
(15) The ability to monitor its operation and report any malfunction to the Maintenance Management functionality.
(16) The ability to ensure that all outputs are consistent, coherent and do not in anyway compromise the safe use of the urban road network, e.g. by ensuring that no green conflicts are produced.

Functional Requirements

(a) when the s&g (stop and go) request data flow is received, its contents shall be implemented
(b) the implementation required in (a) shall be achieved through the output of the data flows to drivers, cyclists and pedestrians
(c) the response to (b) shall be sent to the Urban Traffic Control function using the s&g response data flow
(d) for the "stop" instructions contained in (b), the time for which the stop signal will be present shall be calculated and sent to the Communicate with In-vehicle Systems function in the vehicle s&g input data flow
(e) for both "stop" and "go" instructions contained in (b), the time to the next change shall be calculated and sent to the Predict Host Vehicle Trajectory function in the s&g output for in-vehicle red light warning data flow
(f) if the response from (b) is that the data flows have not been output, data shall be sent to the Maintenance Management functionality using the s&g equipment fault data flow
(g) if no commands are contained in the data flow in (a), or they permit either part or complete local operation, the arrival of the local traffic presence data flow shall be continuously monitored
(h) when the data flow in (g) is received, the instructions in (b) to (f) shall be followed optimising the timings of the "stop" and "go" outputs to give the most efficient traffic flow through the controlled junction
(i) when the local priority request is received in either of the data flows from a pedestrian, a cooperative vehicle or another instance of this function, in shall be implemented as in (b) to (f) above
(j when the local priority request data flow is received from a Public Transport vehicle, it shall be implemented as in (b) to (f) above and take priority over the commands received in (a), (h) or (i)
(k) when the local priority request data flow is received from the Emergency Services, it shall be implemented as in (b) to (e) above and take priority over the commands received in (a), (h), (i) or (j
(l) when the incident warning s&g or urban crossing commands data flows are received, they shall be implemented as in (b) to (f) above
(m the implementation in (l) shall take priority over all other commands
(n) all of the outputs shall be monitored for consistency and coherence, so that for example a green conflict does not arise.

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.
    7.1.0.2
    The system shall be able to implement identified control strategies that conform with specified policy.
    7.1.0.3
    The system shall not do anything to reduce road safety.
    7.1.0.5
    The system shall manage road traffic in such a way that congestion (travel time) may be reduced.
    7.1.3.4
    The system shall be able to activate control devices (e.g. traffic lights, VMS), either individually or in groups.
    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.
    7.4.6.20
    The system shall be able to receive the status of traffic signals/signs that the host vehicle is approaching.
    7.4.8.4
    The system shall enable an emergency vehicle to request a green signal for when that vehicle passes a controlled intersection.
    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.
    7.5.1.5
    The system shall be able to manage the traffic in an area using a number of local semi-autonomous traffic management units, whose rules can be modified when required.
    7.5.2.1
    The system shall enable a road-side device to receive information on the status of traffic signals.
    7.5.2.10
    The system shall be able to warn other vehicles that a green wave is in operation.
    7.5.2.3
    The system shall enable a traffic signal controller to receive a request for a green phase from an approaching vehicle; in the event that more than one conflicting request is received at the same time they shall be prioritised (e.g. emergency vehicles before private vehicles), possibly by the TCC operator.
    7.5.2.4
    The system shall be able to determine the queue length in front of traffic signals in urban areas.
    7.5.2.5
    The system shall enable the traffic signal controller to determine the expected arrival time of a vehicle at the junction using data received from that vehicle (e.g. current location and speed profile, estimated time of arrival).
    7.5.2.6
    The system shall enable the traffic signal controller to inform the driver, via an in-vehicle display, that a green phase will be available when the host vehicle arrives at that junction; this includes the ability to warn that a green phase is not possible.
    7.5.2.8
    The system shall enable a traffic signal controller that has received a green phase request to inform downstream controllers that a green wave vehicle is approaching.
    7.5.2.9
    The system shall be able to keep track of the speed profiles of green wave vehicles between signalised junctions.