Introduction
This section covers Carriageways; specifically their shape and setting configuration.
Introduction
This section covers Carriageways; specifically their shape and setting configuration.
The carriageway functions as a virtual replica of the monitored highway. It is necessary to have a virtual carriageway in order to accurately detect, analyse and report incidents observed by the radar. The virtual carriageway creates parameters around the actual detection area. The ClearWay™ program cannot function without at least one carriageway.
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To move the entire carriageway: Ctrl+Click+Drag when the🕂move icon appears.
For more detailed adjustments, examine the multiple circular icons of differing colours now visible on the carriageway. These points have a number of different functions.
The different functions of the points can be discerned by their colour:
Section Points: pink.
Lane Points: yellow.
Nodal Points: green and blue.
Virtual Area Points: red.
To isolate specific points to make them easier to move, the Point Filter box has a drop-down of options:
Show All: all points visible and available for configuration.
Sections: section points visible and available for configuration.
Lanes: lane points visible and available for configuration.
Nodes: nodal points visible and available for configuration.
Virtual Area: VA points are always visible and available for configuration, despite any of the above being selected. However, this option leaves solely VA points visible.
To move individual points: Click+Drag over the coloured icons. However, certain movements are constrained:
Section points: can only move up and down the carriageway.
Lane points: can only move from side to side of a carriageway, along a node.
Node points: can only move as far as the opposing side of the carriageway. The corresponding VA point moves with a node point, but the opposing node point remains in position - to move one node point just stretches a node.
To move the entire node (both nodal points), select Ctrl+Shift+Click+Drag over the blue node point.
VA points: cannot move inside a carriageway, so a virtual (detection) area is always maintained inside the carriageway and the virtual area is intended to extend the track area outside the main carriageway.
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Select the Carriageway, then select Edit to enter the edit mode.
The editing points will now be visible. Section points are pink. Find a Section point directly adjacent to where you want to add a Section.
Ctrl+Left Click on the Section point. Another Section point will appear to the right of the original point. Left Click+Drag this new Section point to adjust the size of your new Section.
Select Save.
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To Remove a section:
Select the Carriageway, then select Edit to enter the edit mode.
The editing points will now be visible. Section points are pink. Find the Section point of the Section you want to remove.
Ctrl+Right Click on the Section Point. A new window will appear to confirm the deletion of the Section. Select OK to continue.
Select Save.
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Show Section Labels: select this for labels to appear on this carriageway's sections (by default green and numerical).
Enable Queue Logic: select to enable queue recognition software for this carriageway. Once implemented, queues will be be flagged and display visually through an orange fill in the detection area.
Maximum Speed for Queue: the maximum traffic speed for a queue to be recognised in this carriageway. Anything faster will not be defined as a queue.
Heavy Traffic Threshold: the speed at which traffic is considered heavy on this carriageway.
Slow Track Density for Queue (/100m): how many tracks, travelling slower than the maximum queue speed, over one hundred metres, are necessary to considered a section in queue in this carriageway. This calculation of traffic density, as well the average speed of the traffic measured against the maximum queue speed, combine to recognise and alert queues.
Reset Count Down (s): the time necessary to pass, after the queue rule has been broken, without the queue rule being broken again for the queue alert to be lifted in this carriageway.
Enable Auto Queue: select this is you wish to implement Auto Queue for this carriageway. The software extrapolates on existing queue data to estimate potential or unrecognised queues.
Auto Queue Detection Window: how many of this carriageway's sections within every window the Auto Queue studies e.g. 4.
Auto Queue Section Count: how many of this carriageway's sections have to be in an existing queue in order for the Auto Queue to assume the entire window is in queue e.g. 2.
Sensor Allocation Mode:
Nearest: radar detect data from this carriageway's sections assigned to them by proximity (by default).
All in Range: detect data from all this carriageway's sections within their range, sometimes resulting in overlap and double-data.
Default Parameters: the parameters by which this carriageway will detect traffic. A sample selection of detection parameters, including a (default) Default configuration, is available. You are able to configure your own under Tracking Parameters. The default tracking parameters available are:
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Default Debris Parameters: the parameters by which this carriageway will detect debris. A sample selection of detection parameters, including a (default) Debris configuration, is available. You are able to configure your own under Tracking Parameters. The default debris detection parameters available are:
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Statistics Update Interval (s): the period of time between this carriageway's data updates, denoting how often an update occurs.
Statistics Storage Interval (s): the period of time between this carriageway's section data being transferred to the database, denoting how often a data transfer occurs. The data transferred is an aggregate of all the data collected within the time period of the Statistics Storage Interval.
Statistics Stale Timeout (s): the period of time in which no data is recorded from a particular section in this carriageway before it is ignored and not reported.
Statistics Minimum Seen (hits): the minimum number of times a vehicle must be seen before it is considered for section statistics. This provides a useful confidence level for each track, so that only longer lived tracks are counted and used to calculate average speeds.
Rule Update Interval (s): how often the radar checks for rules being broken in this carriageway.
Quiescence Timer (s): the period of time this carriageway must be detected and recorded as empty before it is officially reported as empty.
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Carriageway Traffic Analysis
Vehicle Detection Loops are used to count the passing vehicles at a certain point. The most common detection system is the Inductive Loop, typically installed below the road surface, that uses magnetic fields to detect the presence of vehicles above them through recording spikes in their electromagnetic fields. The sensors can identify static traffic when stationary cars , for instance when waiting at traffic lights, and therefore, can prioritise traffic based on volume.
However, Inductive Loop Detectors only give direct information on the passage of vehicles and presence, and other traffic flow parameters such as density and velocity are inferred from the algorithms that interpret or analyse measured data. When these parameters are calculated from the limited data provided by Inductive Loop Detectors, the values may not be sufficiently detailed for some traffic analysis applications (such as prediction of incidents) or even worse, the information available may be insufficient to support the application.
Furthermore, Inductive Loop Detectors can be negatively affected by changes in their environment, such as deterioration of road surface, inclement weather, and highways maintenance. Due to being installed underground, Inductive Loop Detector maintenance and repair has significant operational costs.
By contrast, ClearWay™ Traffic Analysis functions as a Virtual Loop; not only more time and cost-efficient than Inductive Loops, but capable of producing equally reliable and accurate traffic data. Unlike the Induction Loop, a separate traffic analysis application is not required, as Traffic Analysis is integrated into Witness ClearWay™ if the correct licence has been purchased.
Configuring Traffic Analysis
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Enabled: select to enable the Traffic Analysis Plugin.
Period (s): the period of time the traffic is analysed during.
Sensor Allocation Mode: which radar sensor(s) analyse the traffic.
Nearest: the radar sensor closest to the area or section selected.
All In Range: all sensors that have the selected area or section on their range.
Areas: add and subtract areas in which you wish traffic to be analysed.
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For instance, in this example, Traffic Analysis data is required from a tunnel. Due to track reflections on the tunnel walls, the carriageway detection area has been drawn including the walls to utilise as much of the data as possible. However, this reflected data is inappropriate for use in Traffic Analysis as it would potentially create duplicate results.Instead of an entire Carriageway Section being analysed, the data is instead taken from a Area drawn to include only a single lane of traffic. The data collection for Traffic Analysis will only operate in this selected area.
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Please see Traffic Analysis Plugin for more information.
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Actions
Actions are specific operations that can be carried out in relation to a carriageway. There are four Actions that can be initiated when a carriageway is selected whilst in Configuration Mode.
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There are two Actions that can only be initiated by first selecting Edit, and then the required Action:
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Auto Section: select to divide the carriageway into sections. See the Auto-Section page for further detail.
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