Low Level Function
9.2.5 Manage use of Bus Lanes

Overview

This Function shall be capable of providing the following facilities:

(1) The ability to manage the use of Bus Lanes and when not being used by PT Vehicles to permit them to be used by other Vehicles.
(2) The ability to continuously collect from other functionality the current data about traffic flow through each segment of the road network and the predicted arrival times of PT Vehicles at points along the routes used to provide their services.
(3) The ability to use an appropriate predictive algorithm to calculate the spare capacity in each Bus Lane for a short time in the future (e.g. 15 minutes), both in terms of the numbers of extra Vehicles that can be accommodated, as well as the time for which this spare capacity will exist.
(4) When the Function receives a request from a non-PT Vehicle for a licence to use particular Bus Lane(s), the ability to determine if the presence of the Vehicle will impede the flow of PT Vehicles using the Bus Lane and to grant a licence to the requesting Vehicle if not.
(5) The ability to restrict the licence to the Vehicle that made the request, to a particular Bus Lane(s) and for a particular length of time.
(6) The ability to return details of the licence to the requesting functionality and to send the details to the functionality monitoring the use of Bus Lanes, so that any non-PT Vehicle with a licence will not be prosecuted for illegally using a Bus Lane.
(7) If the traffic conditions for which licences were issued and the algorithms used by the Function predict that the presence of non-PT Vehicles in Bus Lanes will impede the progress of PT Vehicles, or a "critical/emergency" situation arises, the ability to send a message to revoke the relevant licences.

Functional Requirements

(a) when the bus lane use request data flow is received, collect the static data about the bus lane from the store of Bus Lane Data
(b) collect the data about current traffic flow and predictions for the arrival of Public Transport vehicles from the Manage Bus Lane Data function
(c) if passage of requesting vehicle through the bus lanes will not impede the progress of any Public Transport vehicles, and will increase the vehicle capacity of those road segments, then issue a licence to the Manage Vehicle function using the licence output data flow
(d) immediately after (c) send a notification that the vehicle has a licence to use the bus lane to the Bus Lane Monitoring function and to the Manage Bus Lane Data function
(e) continue to monitor the use of the Bus Lane as in (b) above
(f) if the circumstances under which use of the bus lane was granted to the vehicle change such that the progress of Public Transport vehicles will be impeded then revoke the previously granted bus lane use licence and send the appropriate data flows to the Manage Vehicle and Monitor Bus Lane use functions

Diagrams

The Diagram(s) is (are) the diagram(s) where you can find the function :
  • DFD 9.2 Provide Flexible Lane Allocation

    • Parent Higher Level Function

    Input logical dataflows

    Output logical dataflows

    User needs

    Number

    Description

    7.5.3.1
    The system shall permit approved vehicles to use a section of a bus lane when it is not being used by PT or other specific vehicles (e.g. taxis and emergency services).
    7.5.3.11
    The system shall collect traffic information (e.g. number of vehicles, speeds, queue lengths, violation details) on the roads covered by flexible bus lane allocation for statistical purposes, and to improve the algorithms used to decide when non-PT vehicles can use the bus lane.
    7.5.3.2
    The system shall be able to predict the usage of a particular section of a bus lane for a short time into the future (e.g.15 minutes).
    7.5.3.5
    The system shall be able to determine whether there is congestion on the normal road and, if so, whether a temporary licence should be given to the approved vehicle that is making a request to use a corresponding section of a bus lane without causing delays to scheduled PT vehicles.
    7.5.3.7
    The system shall monitor the approved vehicles on the bus lanes and, if its licence has expired, that vehicle will be ordered to leave the bus lane at the end of that section.
    7.5.3.8
    The system shall monitor the usage of the bus lanes, and if a green wave cannot be sustained for a PT vehicle, then approved vehicles shall be ordered to leave the bus lane at the end of that section, and no further licences will be granted until suitable conditions are resumed.
    7.5.3.9
    The system shall monitor the congestion in each section of a bus lane and if a “critical/emergency” situation arises then approved vehicles shall be ordered to leave that section and the up-stream section(s) of bus lanes.