Traffic Signals - Part 17 - Functional Testing

Care needs to be exercised when turning on the signals, preferably this should be done when there is as little traffic present as possible. Use the stage diagram to provide details on which phases will be active in the ‘start-up’ stage, and consider this whilst evaluating current traffic flow when deciding to switch the signals on. However, before the completed traffic signal installation can be switched on, it is necessary to inspect and test it as detailed in the previous chapter. This will ensure that the equipment has been correctly installed and is safe to carry out functional testing of the installation.

The first thing to do when switching on is to verify that the controller is cycling and which mode of operation is active. If the site will normally operate under SCOOT or MOVA, then it is unlikely to be in that mode at this point, because the O.T.U. or O.M.U. will not have been commissioned yet. Because of this, the TSC is likely to be operating under a lower priority mode, such as Vehicle Activated, Fixed Time or CLF. Observe the signal displays and the manual panel to confirm that the signals have cycled a few times, before proceeding. If the TSC fails to do this, check the mode selection on the manual panel, and interrogate the system to ascertain which mode the controller is in and if any faults are present in the fault log.

‘New Traffic Signals Ahead’ | Inspecting and testing a new controller | Getting ready to switch on

The first item to test is to confirm the operation of all the pedestrian demand units and indicators and to ensure that all audible or tactile unit are operational and active during the relevant ‘Invitation to Cross’ period.

Where present, the operation of Red Lamp Monitoring will need to be tested to ensure that the system correctly reports faults and inhibits phases or shuts-down. Firstly the lamp loads should be checked, to ensure that the system is recognising the correct numbers of signals on each phase. For each phase which is subject to Red Lamp Monitoring, disconnect a single red aspect, and monitor the fault log to observe that a fault is detected when the red aspect is illuminated. Whilst testing the Red Lamp Monitoring, also ensure that the TSC DFM indicator flashes when a Red Lamp Fault is active in the fault log. Refer to the Controller Specification, and determine if an extended inter-green period from the affected phase to protected phases should be active, if so time this period to confirm that it is operating. Next, disconnect a second red aspect on the same phase and observe that the correct fault is detected in the fault log and the relevant action is achieved. For sites where there are pedestrian facilities with audible / tactile signals at signalised intersections, the protected phase will be inhibited. At stand-alone signalised crossings and part-time installations, the signals will extinguish. Reconnect the red aspects and follow the TSC instructions to clear the faults and resume operation. Allow the TSC to cycle at least once, before repeating the process for all other Red Lamp Monitored phases.

The DFM indicator should also be observed to illuminate steadily, when Detector Faults are present in the fault log. To activate this, some TSC’s provide a test facility to accelerate the absence monitoring period from hours to minutes. Even so, it might be preferable to temporarily reduce the fault monitoring period for a single channel of detection down to one hour. This would then activate after just one minute of inactivity. Alternatively, reduce the permanent presence period to one minute, and then ensure that the relevant input is active for long enough to trigger the fault. This is easy to achieve with a pedestrian input by keeping the push-button pressed in. Once completed, clear the fault log and reset any temporary changes made, and ensure that demands are operating correctly on the affected input.

The operation of signal dimming should be tested by covering the solar cell and observing the operation of the signal displays. It should be noted that some TSC’s incorporate up to a one minute delay between the solar cell changing state and the signals being set to dim or bright.

The Zone of Detection (ZOD) for each pedestrian above-ground detector should be checked and adjusted. The detectors are equipped with an LED to show when they are in a detect state, which can be used to verify the operation of the equipment. Some systems also provide computer based software packages which connect to the individual above ground detectors by a wireless Bluetooth connection or cable to physically set the ZOD and to monitor the operation during testing. Other systems do not provide this facility, and rely on the physical orientation of the above ground detector to set the ZOD. Whilst monitoring the above ground detector activity, have a ‘test’ pedestrian walk through the centre of the ZOD, and verify where the detection state starts and stops. Also test the outer limits of the ZOD, to determine that the above ground detector will reliably operate over the full extent of the desired area. It is also important to ensure that the above ground detector does not operate outside of the desired ZOD. For kerb-side detectors, the ZOD should extend across the full width of the waiting area and should be fully functional in the vicinity of the pedestrian demand units. The depth of the ZOD should extend for a minimum of 2m, but should not extend beyond the kerb-line, to ensure that it is not triggered by passing vehicles. For on-crossing detectors, the ZOD should extend between the crossing stud-lines across the carriageway. The tests will need to be done on multiple occasions and the above ground detector adjusted to ensure that the resultant ZOD provides reliable operation.

The Zone of Detection (ZOD) for each vehicle above-ground detector should also be checked and adjusted. The required ZOD will be dependent on the application it is being used for. Refer to the SLD for full details of the designers requirements. Presence detectors are typically used to act as stop-line detectors, whereas dynamic detectors are usually used for System ‘D’ type applications for approaching vehicles. Care should be taken to ensure that the units are not obscured by backing boards or overhanging foliage. Also make sure that each unit is setup to detect vehicle movements in the correct direction and are not suffering from ‘false’ triggers caused by vehicles in adjacent lanes.

Where present, the operation of the Safety Isolation System should be fully tested. This is achieved by disconnecting the inertia sensor in the protected pole, which should trip all the associated circuit breakers for that pole. Each used core in the pole (including Neutrals/Commons) should be electrically isolated, only the Earth connection should be retained. Also ensure that there are no spurious breakers triggered for other poles. Verify the status indicators in the equipment and fault log entries, before reinstating the inertia sensor. It will then be necessary to clear the fault both within the Safety Isolation System and the TSC. Repeat for each protected pole.

Interrogating a TSC | Functional testing in progress

The operation of linking facilities, such as Local Links or Pedestrian-Links (if present) would require thorough testing to ensure correct operation. These normally consist of multi-core cables, with individual cores being switched with 24v to signify the status of a required facility. It is necessary to ensure that each input/output provides the correct operation on the relevant bit. To ensure these are working correctly, ensure that both ends of the link are inspected and tested. In addition to Local-Links, full data connections, such as RS485 links allow engineers to interrogate the maintenance engineer’s handset facility for a TSC from another controller cabinet. This type of facility is normally only provided where multiple TSC’s are used as part of a closely linked operation, such as large MOVA installations on motorway junction roundabouts. To test this facility plug the remote end into the handset port of the TSC and then interrogate the local end of the link. Then repeat the test from the remote end.

Some TSC’s include a wireless handset communications facility to allow engineer’s to interrogate the system without having to have the cabinet door open. This is obviously beneficial during inclement weather, but needs to be fully set up and operational beforehand. The set-up and operation will be dependent upon the manufacturer, but should be able to provide full access to the maintenance engineer’s facility of the TSC via a wireless link. The expectation for this facility is that it will allow an engineer at least 10m from the TSC cabinet, and ideally sat in their vehicle to access the system. Ensure that any log in information for the communications is recorded, such as IP or IDENT address.

The communications connection for the TSC will need to be tested to ascertain that it is fully operational. Traditionally, TSC’s were connected via a leased line back to the UTC Centre, however, these days it is becoming normal to utilise a wide range of communications technologies, including; land line, GSM, broadband, fibre-optic and MESH. Advice will need to be sought to ensure that the communications system is fully commissioned and operating correctly, but ensure that information such as telephone numbers and IP addresses are recorded. Many installations also include peripheral communications equipment, such as patch trays and routers. Again, seek advice to ensure that these are fully commissioned and operating correctly.

Once the communications connection has been proven, the Outstation Telemetry Unit (O.T.U.) or Outstation Monitoring Unit (O.M.U.) will also need to be fully tested. These units will require the UTC and Remote Monitoring Systems to be set up beforehand to enable the required functionality to be achieved.

For O.T.U. operation (which will normally be used to run the TSC on UTC / SCOOT, contact the UTC centre, and get a prepared plan running for the site. This should force the TSC into UTC mode (refer to the mode priorities table), and allow the controller to cycle. Whilst talking to the UTC operator, monitor the control and reply bits being sent and received by the UTC centre compared with the operation of the TSC on site. Also monitor any miscellaneous control and reply bits. For SCOOT installations, also ensure that the SCOOT loops on the site are operating and being received by the correct bits on the UTC system. Ensure that any additional information for the O.T.U. is recorded, such as Type, Firmware No, IP address.

For sites with an O.M.U. the testing will be dependent upon the form of operation required. Where the O.M.U. is just used for the Remote Monitoring System (RMS), manually set faults in the TSC and whilst talking to the UTC centre, ensure that these are shown on the RMS. For sites which will operate under the MOVA method of control, the O.M.U. will require the MOVA dataset to be uploaded to the unit, and the operation of the system tested in a similar way as the SCOOT testing, but verified internally by monitoring the operation of the Control and Reply bits at the O.M.U. Ensure that any additional information for the O.M.U. is recorded, such as Type, Firmware No, License No, IP address.

Any further ancillary equipment, such as CCTV should be tested at this point. The operation of the camera should be monitored from the UTC centre to ensure that images are received and that control of any facilities, such as Pan, Tilt, Zoom (PTZ) are operating correctly. Ensure that any additional information for the CCTV is recorded, such as Type, Firmware No, IP address.

The base of the controller cabinet should now be sealed; including spare and utility ducts.

Ensure all paperwork is complete, and sign off copies for the signal company and client acceptance certificates.

Once the functional testing is complete, the operation of the installation will need to be observed and validated to ensure that the operation is as efficient as possible. The exact requirements for this will be dependent upon the method of control used at the site, but should as a minimum normally consist of validating the operation for an AM and PM Peak period and an inter-peak period. It is also normal to carry out a further validation after three months of operation, once drivers have had an opportunity to get used to the installation. Once operating, it is good practice to further review the operation of installations on a periodic basis, to ensure ongoing efficiency is achieved.

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