Permanent Intelligent Transport System (ITS) applications have made great strides in the past decade, but when it comes to applying proven ITS technology on a portable basis within critical road work areas or regions where severe weather conditions, such as poor visibility (fog) adversely affect driving conditions, the industry still has much to do. Road works areas are often the most critical, due to their unpredictable, non-recurrent congestion and reduced capacity.
Mobile ITS systems have been widely implemented in the U.S. market for the past 5-10 years and offer virtual Traffic Management Centre resources across multiple jurisdictions and agencies. The motoring public are not concerned with who owns and manages the roadway, just in having real-time information to better plan their trip or to prepare for travel delays or unanticipated queues.
Mobile ITS System Features:
Successful mobile ITS applications should include many key elements / features to help promote better safety and mobility. These systems need to offer real-time information for multiple types of applications utilizing the same overall system hardware. They should also utilise any proven sensor technologies and blend multiple types of sensor data / traffic information. The equipment needs to be capable of operating 24 hours a day, seven days a week. Each device should be equipped with a high speed modem that has GPS.
Mobile ITS should be capable of providing real-time automated traffic email / SMS text alerts to key personnel when speeds and / or journey times or other traffic incident data exceeds acceptable user-defined thresholds. Although ANPR is widely used, it does have limitations in the ability to provide real-time data. ANPR uses historical journey time information as it is dependent on a vehicle passing through defined points and then calculating the time taken to travel that distance. It is more important to evaluate the system needs / goals and then use the type of sensors which best accommodate the desired outcome.
For example, if real-time traffic data is required through road work’s, then using mobile traffic sensors (Doppler, Microwave, Bluetooth, ANPR) ideally placed every 750 – 1000m in areas of concern, alongside mobile VMS and mobile CCTV trailers, will allow the evaluation of a roadway system and whether sensors will become part of the future permanent infrastructure. Mobile VMS should be placed at key upstream decision points and be placed often enough that the real-time information is relatively current for the next 4 – 6 miles +/- downstream. Mobile CCTV trailers should be placed in areas of concern to allow for visual verification of automated system alerts. Project managers can then evaluate if the system data should be integrated into the local Traffic Management Centre (XML / API data stream) or if a virtual TMC software approach is desired, or both.
The ability to push / pull real-time traffic data with one or multiple Traffic Management Centres utilizing an API or XML format is a key feature of a successful mobile ITS system. This allows sharing and integration of system information with permanent ITS systems, in road works areas that may have insufficient sensor coverage or that may require additional message signs to convey key traveller information in areas not covered with overhead Variable Message Signs (VMS).
Mobile ITS System Applications
Mobile ITS systems need to be easily scalable to fit the needs of a specific project and each phase of that project. Adding, subtracting or relocating devices should be easily accomplished. One deployment can serve multiple purposes, thus delivering more benefit for the cost. For example, a Journey Time system could also be programmed to provide vehicle-specific high speed warnings to only those entering the road works at a user-defined unsafe speed. Equally, when congestion builds, the journey time messages could switch to queue warning messages letting motorists know they are approaching slow/stopped traffic. This same system could be used in areas where visibility is reduced at times due to fog, surface water etc. and automatically change Variable Speed Limit signs in advance of the area.
Most road works crashes are rear-end accidents (30-40%), Queue Warning systems are often the most cost-effective and can reduce rear-end type incidents by 20-60%, which not only reduce delays for all other approaching motorists but also makes the works area safer for motorists and workers.
Another variation of a Queue Warning system is a Dynamic Merge system, which encourages early merges when free flow traffic exists and then alters messages when the area is congested, to direct motorists to utilize all lanes until the merge zone. Studies have shown this type of system actually allows 10-15% more traffic flow compared to un-directed traffic flow.
Mobile ITS for adverse weather warnings
Another application of mobile ITS is the management of adverse weather situations such as reduced visibility due to seasonal fog. It is widely agreed that visibility and other roadway weather situations can adversely affect driver behaviour. Portable, easily deployed ITS applications play an integral role in the operational framework for roads where adverse weather conditions have a direct impact on motorists. Employing mobile ITS technology along a designated route can have a dramatic roadside impact, informing motorists of adverse weather conditions, such as low visibility due to fog and surface water thickness, and the subsequent effect on braking distance. A simple real time warning system can dramatically affect driver behaviour and actively encourage motorists to reduce speed by providing timely information on the situation further downstream.
Across the UK, Fog is a common and recurrent phenomenon causing a sudden reduction in visibility conditions on highways. The international definition of fog is a collection of water particles that reduces visibility below 1 km (National Oceanic and Atmospheric Administration, 1995). Heavy surface water can cause similar problems in relation to visibility and, in addition, breaking distance. These factors can lead to an increase in crash levels (Abdel Aty et al, 2010). Effect of fog on driver safety and related crashes was studied in great detail in the UK by Moore and Cooper, 1972. They found that even though traffic reduced by 20% under foggy conditions, the total number of crashes leading to injuries increased by 16%. Crashes occurring under foggy conditions frequently involve multiple vehicles (Summer et al, 1997). One of the most obvious factors concerning fog is that it is frequently more prevalent during the winter months so a temporary ITS application is an effective way of controlling fog related incidents during key winter months when visibility is worst.
Quite often, visibility is worst on roads which do not have a suitable fog detection and warning system. The use of mobile VMS and speed sensors for pilot projects enables road engineers or consultants to choose the best location based on specific site needs. Trailer based mobile variable message signs (MVMS) can be placed upstream of existing weather stations equipped with visibility sensors. Fog sensors can even be mounted on traffic sensor trailers or VMS. The distances between signs and warning devices should be based on road speeds or alternative routes available and be sufficiently in advance to allow drivers time to take the appropriate action. For example, if the normal action is to just reduce speed, then the advance warning distance is less. This can all be determined on a trial basis using Mobile VMS and an operating system like Mobile VMS JamLogicTM which supports information from visibility sensors. The addition of mobile speed sensor trailers provides a secondary method to detect a problem and also monitors traffic flow during a fog event to help traffic control engineers tweak the logic applied to better tune the system. The report following a trial can then be used as a cost efficient model to evaluate whether motorists reduce their speed as a result of being informed of fog and if effective, to promote deployment of permanent ITS technologies.
Advancement of Mobile ITS Systems
For mobile ITS systems to become more widely utilized, the industry and leading professional organisations need to encourage and provide guidance on when mobile ITS systems are recommended / cost justified. They also need to provide sample specifications that can be utilized for commonly deployed systems, such as for Automated Queue Warning systems and Journey Time systems. These specifications should only include proven system providers and should be performance based and focused on the system goals/needs and not on specific hardware or technologies. An example of this would be to require 10 metre camera trailers with cameras that can provide at least 1 fps (frame per second) over a digital cellular network, 360 degree continuous panning and provide a minimum of x18 optical zoom etc. Historically ITS professionals have simply and incorrectly cut and pasted CCTV specifications from permanent projects with no consideration for power efficiencies and minimizing bandwidth (both of which are important considerations for longer duration mobile deployments).
The U.S. FHWA (Federal Highway Administration) published the “Work Zone ITS Implementation Guide” in January 2014 and provided guidance for such efforts. This document details all possible considerations for those planning to implement these type of systems and most importantly provides a Work Zone ITS feasibility score sheet to aid in determining when this type of system should be considered for use. This report identifies a 6 Step Process:
- Assessment of Needs
- Concept Development & Feasibility
- Detailed System Planning & Design
- Procurement Methods
- System Deployment Considerations
- System Operation, Maintenance & Evaluation
The U.S. FHWA has also implemented advanced initiatives and special funding to encourage additional utilization of “Smart Work Zone” systems for the following specific applications:
- Automated Queue Warning Systems
- Variable Speed Limit Systems
- Dynamic Merge Systems
This program is part of the FHWA’s “Every Day Counts” (EDC-3 Initiatives)
Ultimately mobile ITS systems are designed and intended to provide detection and automated alerts to increase safety and mobility in advance of and through a road works area. These areas are the most critical in each agency’s overall network or extended network and thus deserve more attention and effort utilizing ITS technologies that are proven and cost-effective when properly designed and procured to provide safer roads and more efficient traffic flow.
For further information on specific projects and trials or for details on any of our VMS or ITS products please contact Michelle Curran
Tel: 01753 303900 / 028 30440001
Mobile Variable Message Signs Ltd.