Introduction

The ClearWay™ Traffic Analysis Plugin is a powerful reporting tool enabling the user to create virtual Vehicle Detection Loops, to count and assess vehicles travelling on a configured area of a carriageway section using radar.

The traditional 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, are 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™ is not only more time and cost-efficient than Inductive Loops, but utilizes radar to replicate these sensors, counting the number of motorised vehicles, categorising them by size (which is defined by the user) and calculating their average speed per classification. ClearWay™ utilises its ability to monitor and track vehicle movement over large stretches of the highways to build an accurate picture of traffic conditions and highway utilisation.

Contents

Selecting Where to Monitor Traffic

The selection of the areas where you monitor traffic is critical to overall performance of the Traffic Analysis system. There are two main considerations when deciding the optimal location to monitor the traffic:

1. Clear view of all vehicles: Ideally you want a good view of all vehicles in your designated analysis areas. This way you can clearly see them to count and calculate their size. A location closer to the radar where the radar can see over smaller vehicles and can easily discriminate between vehicles is recommended.

2. Overall visibility of a vehicle: This is about being able to see as much of an individual vehicle as possible so ClearWay™ can make a reliable assessment about its size. When vehicles are closer to radar and at a slight angle then the radar is more likely to see the side, rear and top of the vehicle. This gives the radar the best opportunity to assess the size of the vehicle.

Given these factors we recommend establishing either one or two analysis areas about 25 - 75m away from the radar. If you need to use two analysis areas then setup one either side of the radar at the recommended distances, as illustrated below:

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Traffic Analysis Monitoring Areas

You have four options for traffic analysis monitoring:

Sections

These are typically evenly spread along the carriageway and by default are about 100m in length. You can select one or more sections in which to conduct analysis, but as already mentioned we recommend one or two sections either side of the radar. Please refer to: Traffic Analysis Plugin | Adding Sections

Areas within a Section

If the sections are not in quite the correct location or perhaps not the right size you can also specify custom areas for traffic analysis. You must still select the sections in which you wish to operate the traffic analysis, but you can refine the coverage by applying a custom area over the selected sections. In this scenario, custom areas can only reduce the analysis area size i.e. smaller than a section. Please refer to: Traffic Analysis Plugin | Adding Areas within a Section.

Use Areas Only

Custom areas can be used on their own, so one area could span multiple sections. You will still be required to specify a section but this will only used for reporting (when Use Areas Only is specified) and it is not used for track capture. Please refer to: Traffic Analysis Plugin | Use Areas Only

Lanes

A lane can be selected as an additional filter for Traffic Analysis. Please refer to: Traffic Analysis Plugin | Adding Lanes.

Creating Custom Monitoring Areas

Once you have identified the sections to monitor you can add new custom areas and apply these to the Traffic Analysis configuration:

1. Create a new area of type General.

2. Modify the area size and position to cover the required location on the highway.

3. Save the new area to be added to the Traffic Analysis Areas list.

Here Area A and Area B are in Section 4 of the carriageway, and are coloured in red. As discussed we recommend that no more than two areas are configured for the radar, as this should give the most accurate analysis of the traffic.

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Plugin Configuration

To configure the Traffic Analysis Plugin:

1. Ensure Config Function is enabled.

2. In the Configuration Tree, select the Carriageway in which you want to enable the plugin.

3. Click Edit to amend the default settings - the Traffic Analysis has it’s own section on the carriageway edit screen:

Global Config

These are the settings that you can amend for your Traffic Analysis:

Enabled: This is selected by default.

Minimum Sightings: This is the number of sightings required of each vehicle before the system calculates the average across these sightings. By default, the setting is 4.

Use Areas Only: This option only uses Areas for track capture. If selected, the Areas list will no longer be available underneath the Size Normalisation Parameters section as it no longer relevant, but there will then be an option within the Section Configuration to select an area.

Use Debris Tracks: The debris detection system utilizes a dedicated processing channel within the Radar Tracker, and can be utilized by the Traffic Analysis Plugin if desired. As it only detects stationary objects, it is recommended that it is not used, and is therefore not selected by default.

Track Length Type: There are four options for the radar to measure the vehicle length. The default setting is Diagonal, and is the recommended setting as it usually offers a more accurate assessment of the size of the vehicle whilst travelling past a radar.

Diagonal: This is the hypotenuse of the target, using the azimuth and range measurements to calculate it.

Range: The measurement from the radar in a line away from the radar.

Azimuth: This is a measurement of the target at right angles to the radar.

Normalised Diagonal: This uses an algorithm to correct the azimuth size for a given distance from the radar. This is still combined with the range to calculate the diagonal.

The image below shows the desired option depending on where the area is situated in relation to the radar:

Use Harmonic Mean: This option will use the harmonic rather than arithmetic mean to calculate average track speed. By default this is not selected.

Send Immediately: A report including each size classification, count and average speed is generated for every Period set in the Period setting. The option to send immediately, will send an individual report for each section to an external system immediately with no aggregation.

Period: This is the number of seconds for each reporting period.

Size Normalisation Parameters: These settings are for internal use only and will be removed at a later date.

Areas: If the Use Areas Only option has not been enabled, then you can select an area on the section of the carriageway to monitor. These will have been previously configured (see the example at the top of this page).

Size Classification: This classifies the vehicle sizes in meters, and there are four entries in the section by default; Short, Medium, Long and Combination. these can be added to or deleted as required. The smallest vehicle that the radar can detect with this plugin is a motorbike, and this would fit into the Short category, for example. These classifications are configurable and all the defaults can be removed if required. The user is free to add whatever size classifications they feel is appropriate for their own analysis.

Adding Areas within a Section

1. To add a Traffic Analysis monitoring area within a section, use the button:
   
   

    

2. This will open an area dialog allowing you to select the desired area:
   
   

    

    

3. Click OK and repeat for other areas to monitor:
   
   

    

Adding Lanes

1. You can add a lane as an additional filter, if desired, by using the button:
   
   

    

2. This will open a lane dialog allowing you to select the desired lane:

    

    

3. Once you have finished click the Save button:
   
   

    

4. The newly configured lane will be displayed:
   
   

Section Config

The section configuration has it’s own tab within Traffic Analysis.

Section: Choose the section to add to the Section Config list.

Ignore Area Filter: This option allows any sightings in the section to be counted in the sections statistics, even if areas are not configured. If this setting is disabled, then a sighting must be in a configured area to be counted in the sections statistics.

Override Name: This overrides the name of the section.

Override Length Type: This overrides the default track length calculation type for this section.

Override Size Classification: This overrides the size classifications for this section.

Adding Sections

To add one or more sections:

1. You can select the section of the carriageway that you wish to monitor by clicking the button:
   
   

    

2. This will allow access to further options. Click on the Sections box to display each of the sections of the carriageway for you to choose from:
   
   

    

3. You can then edit the override settings for the section as desired.

4. Repeat these steps to add additional sections. To delete a section, highlight it and click the button.

Use Areas Only

To use only areas for Traffic Analysis:

1. Select Edit to be in edit mode:
   
   

    

2. Select the Use Areas Only check box:
   
   

    

3. Select the Section Config tab and then click the button:
   
   

    

4. This will reveal the options available:
   
   

    

5. Clicking in the Area field will open a dropdown allowing you to select the desired area:
   
   

    

6. Select the desired area and then choose the section that will be used for reporting purposes only:
   
   

    

7. Select the section and you can then choose more options if required:
   
   

    

8. Repeat these steps to add more areas. To delete an area, highlight it and click the button.

9. Click Save:
   
   

    

10. This will save the areas to be used for Traffic Analysis:
    
    

Additional

Traffic Analysis takes data from a specific location over a specific period of time, and then aggregates this data into the vehicle classifications defined within the configuration. In ClearWay™, the carriageways are divided into Sections and therefore it is logical for the sections to function as the specific locations from which Traffic Analysis data is taken. There are also situations in which pulling data from Areas instead of Sections is preferred. The configuration allows you to use either or both.

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 an area drawn to include only a single lane of traffic. The data collection for Traffic Analysis will only operate in this selected area.

Traffic Analysis Results and Reports

There are two options for finding and displaying the results from the Traffic Analysis Plugin:

• Running a query in the Playback tab using Carriageway Traffic Analysis.

• Using ICD-001 Protocol to generate a Classification Report, which includes data including vehicle classification, average size, average speed, total tracks and location data.

Carriageway Traffic Analysis Query

To run a Carriageway Traffic Analysis Query:

1. Select the Playback Tab

2. Check the Carriageway Traffic Analysis check box.

3. Carriageway: Select the Carriageway that you wish to analyse which has been configured in the Plugin section.

4. Section: Select the Section that you have configured in the Plugin section.

5. Lane: Select a Lane, if required, from the dropdown list.

6. Click the Query button to run the query.
   
   

    

7. This will produce a graph like the example below, with a Total Count and Speed m/s:
   
   

Each of the Size Classifications have their own tab, and the report can be exported to a .CSV file using the Export button, like the example below:

ICD-001 Classification Report

The Interface Control Document (ICD) 001 describes the structure and sequence of data for communication between the current Witness software systems and third party software systems.

ICD-001 Protocol can produce a Size Classification Report in XML which can be sent at regular intervals to one or more external systems. An example of the report structure is illustrated below:

For more information on ICD-001 Classification Report please refer to ICD-001 Classification Report. Refer to Navtech ICD-001 Protocol for more information on the ICD-001 Protocol.

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