Maintenance activities on ITS devices and traffic signal systems can impact on Road Network Operations. When ITS is first deployed, the equipment is new and does not require extensive maintenance resources. As systems expand and age, there is a continuing need for – and complexity of – maintenance operations.Two aspects of maintenance have a direct impact on operations:
There are two types of routine maintenance: preventive and responsive.
Preventive Maintenance is generally regularly scheduled maintenance designed to pre-empt device failure that would render the device unserviceable. Preventive maintenance will extend the active life of devices and subsystems. It can use past experience to anticipate when devices should receive attention. Automated maintenance management systems base the scheduling on a number of factors that are analysed by the software to produce a schedule.
Preventive maintenance can be as simple as cleaning cabinets and cable runs/conduits, securing wiring and printed circuit board connections, to scheduled pre-emptive repair. Alternatively it can entail replacement of components or entire devices.
Responsive maintenance (or reactive maintenance) concerns the repair or replacement of a component or system following failure or damage caused by a collision or other incident. Failed ITS equipment and non-functioning network monitoring devices will not provide the images, data or information needed to help maintain stable traffic flow.
When failures occur the devices cannot perform their functions, which will often be detrimental to RNO. Responsive maintenance should be the highest priority, since restoring equipment function is the key objective. It is advisable for TCC operators to prioritise conflicting maintenance needs, rather than leaving maintenance staff to determine this themselves.
The key to successful maintenance is to have a complete, manageable inventory of all devices. Automated support software can be an ideal way to maintain the inventory – and can also assist in preventive and responsive maintenance operations. (See Data Management and Archiving)
Florida Department of Transportation provides an example of a combined ITS Maintenance Management Systems (MMS) and Fibre Management Systems (FMS), known as the ITS Facility Management System (ITSFM). (See http://www.dot.state.fl.us/trafficoperations/ITS/Projects_Telecom/ITSFM/ITSFM.shtm)
Factors that lead to the adoption of an automated maintenance system include:
Most Traffic Control Centres (TCCs) have “up-time” targets for system availability that challenge the maintenance team to keep devices operational at least a certain percentage of time, for example, 98% or 99% availability. Only automated systems can both organise the maintenance activities and keep track of them. An ITS maintenance management system and a communications management system are part of the ITS operation, just like the TCC software. If the RNO organisation operates its own comprehensive telecommunications networks, this will justify a telecommunications “network manager”, which is common place in the telecommunications sector.
Systems maintenance can be performed either by in-house staff or outsourced to others—usually original equipment suppliers but also third party maintenance companies. In some regions the trend is towards outsourcing systems maintenance to private contractors. The substantial differences in the nature of ITS and roadway maintenance, generally leads to ITS maintenance being outsourced to a specialised electrical contractor.
Some large consulting firms are increasingly expanding their involvement in this business, sometimes called asset management.
The purpose here is to maintain ITS equipment or restore it to a condition that can effectively handle the assigned functions, at the lowest possible cost. To achieve this objective, the operator must:
Organisational arrangements will depend on the size of the maintenance operation, the volume, nature and location of equipment, and the resources and skills available. Organisations will need to determine the scope of maintenance activities to be undertaken internally by the operating organisation and those that will be sub-contracted.
Effective maintenance is based primarily on detailed wording of supply contracts, follow-up and effective handover. This is to ensure a precise definition of the work to be performed, conditions of delivery, contract deadlines for restoring service and penalties for non-compliance. It also relies on:
Motorway Maintenance Management Systems (MMMS) generally operate on limited-access roadways, which carry high volumes of traffic at relatively high speeds. Disruption to traffic adversely impacts traffic operations. Fortunately, many ITS devices are located off the roadway, but within the rights of way, so maintenance activities can be conducted without directly interfering with traffic. Even in these cases temporary traffic control devices may be required for the protection of the maintenance crew. Efficiency of maintenance operations is essential.
The mere presence of maintenance vehicles causes driver distraction (“rubbernecking”), in the same way as roadside incidents. This is a particular concern in restricted situations, for example part of a tunnel or long bridge. Working on, or adjacent to, live carriageways is hazardous and some simple precautions are needed – for example, high visibility clothing, hazard lights and deployment of temporary traffic management to close lanes.
There is greater traffic disruption when the maintenance crew must work over an active lane or median shoulder, such as on the exterior of a VMS. When this happens, the crew is generally required to close the lane(s) over which they work and deploy temporary measures to maintain traffic flow. This work should, whenever possible, be done during off peak times to minimise the adverse effect on traffic. The work is often contracted out to specialist firms to provide temporary traffic management. The TCC will need to be vigilant in ensuring that measures to maintain traffic flow are in place and are operating effectively at all times.
These considerations apply equally to maintenance of routine traffic control and information devices, such as fixed signage – so general maintenance should follow the same practices as the ITS maintenance agency. The TCC should be notified whenever there are activities on the motorway, particularly if lanes are to be closed. Some countries use Lane Closure Management Systems to schedule and manage closure requests and contractor roadwork.
Particularly dangerous work sites – for example on one of the traffic lanes – should be protected by a crash barrier (crash-attenuator or crash cushion) such as a vehicle or trailer positioned upstream of the lane closure. In Santiago, Chile, one of the urban toll road operators requires all providers of maintenance to equip work crews with such equipment.
The primary difference between motorway and urban arterial road networks is that in the urban situation considerably more maintenance has to be done on, or immediately above, the roadway itself. Traffic signal heads, supporting span arms, signs, wires and overhead vehicle detectors are all located over the roadway. Devices off the roadway, such as signal cabinets and other ITS equipment, will also generally be located in less open spaces. If a hard shoulder is not available it is likely they must be accessed from a traffic lane. Lane closures are far more likely on urban arterials roads and city streets.
Many high-capacity urban arterial roads experience traffic speeds that are not significantly slower than a motorway. Other roads have lower traffic volumes, particularly off peak, and traffic speeds may be lower too. Temporary traffic management is important and without it, conditions may be unsafe. The number of movements possible (such as driveways and turning movements) also greatly increase hazards. The paramount objective must be the safety of the maintenance crew.