Tools to support operational decisions in winter maintenance can remove subjectivity and increase efficiency;
Far from being a financial burden, close monitoring of road surface conditions is actually a cost saver, says Danny Johns, Offering Manager with weather monitoring specialist Vaisala. He points to the material cost savings achieved by the Idaho Transportation Department (ITD; see Sidebar, 'Idaho District 4: a 40 per cent materials saving') as an example of what can be done.
Vaisala is now building on the thermal mapping surveys which it has offered customers for the last 20 years and offering to the market support systems which are intended to remove subjectivity from decisions on when and how to treat road surfaces (see Sidebar, 'Next steps in decision-making').
Moving targets
Thermal mapping has long served as Vaisala's infill mechanism between fixed RWIS sites. Surveys of road networks in a given area of operations are conducted over a series of winter nights in order to build up a better picture of localised conditions. It is common knowledge that bridges and elevated sections are especially prone to icing but even the presence of trees at the roadside can have an effect on temperature. Taken across a given geographical area, it is not uncommon to have a variance in road surface temperature of up to 10oC due to the geometry alone.
"Overall it's a very involved business but with all of the right tools in place you can progress from a reliance on general weather information, and reactive or blanket responses, to a situation where you only have to salt proactively at a handful of sites," says Johns. "The ultimate goal is improved safety with the best use of often limited resources. On a marginal night when temperatures are hovering around freezing, you don't want to salt unnecessarily but if the forecast is out by even half a degree you can end up with serious problems."
Mobile assessment is already a possibility. For example, the ITD is just one of a growing number of jurisdictions which choose to patrol vulnerable points on their networks looking to verify road weather data using mobile systems such as Vaisala's DSC111 surface state measurement sensor, which can identify the presence of moisture or crystalline/solid ice on the road surface. All correlate to grip and a loss of friction which needs to be addressed.
But decision support systems are the next big thing, according to Johns.
Coping with the deluge
"There's a push, especially in the US, to come up with something which helps the decision-making process," he says. "There's an awareness of the absence of an 'extra leg', a tool with which to gather and process all available data. Data deluge is already a problem; as well as the better-quality information which continues to become available from national weather services, the numbers of fixed RWIS systems and cameras also continue to increase. Time is an issue, in that someone has to collate and understand these increasingly large amounts of data in a relatively short space of time. From a forecast at noon, decisions have to be made over the afternoon on where to deploy vehicles and which chemicals to use; whereas in Europe salt is the predominant choice down to about -7oC, in the US other agents are sometimes used because of extremes of temperature.
"The emerging generation of decision support systems synthesise data into meaningful results - effectively saying 'treat this route, with this chemical, at this time'.
"Products such as Vaisala's IceMan, a password-protected, web-based centralised database for winter maintenance service operations, have been used for over a decade to record actions and facilitate information-sharing.
"IceMan logs decisions made rather than advising. The new decision support systems are more of a real-time tool but aren't intended to make decisions as such. They're intended give order and promote consistency by providing an all-encompassing vision of what's going on."
The newer solutions raise some legal issues which still need to be fully addressed - for instance, what happens if an operative goes against the support tool's advice. Future developments could include real-time information to the vehicle cab on a route-by-route basis but Johns notes that there remains a need for human interaction in the winter maintenance process - overseeing, checking and so on. Automation, he says, is possibly unachievable but should be an aspiration.
"In practice, gritter tracking isn't quite 'there' yet so there is still the opportunity for things to go wrong in an operational environment. However over the next one to five years I can see decision support systems playing an increasingly larger role."
Simplifying the process
Forecast definition, meanwhile, is getting better all the time. Johns: "Go back about seven years and resolution in developed countries was at the 12-15km level. Now, 2km is possible. The digital camera provides a good analogy - we're seeing higher and higher availability and greater and greater accuracy.
"Predicting where things will go from here is difficult. Five years from now, supercomputing could have moved on substantially. The same applies to mobile communications. If anything, the data overload issue is only going to get worse."
Vaisala provides customers with meteorological and scenario training as, Johns says, it is very important to have them understand the capabilities being delivered. Decision support systems, however, will take on a greater portion of that burden.
"That reflects what we learn from user groups," he continues. "The recurring message from customers at present is 'make things simpler for us'."
Technological advances come at a time of greater global awareness of the effects of weather on transport networks.
"Traditionally, the focus has been on winter and that will continue," Johns adds. "But along the way, climate change has meant that wind, fog and extremes of heat are also all gaining in importance. If there are severe traffic hold-ups during hot weather there might be a need to get water to those stranded, for instance - it's those sorts of events which we'll need a greater appreciation of in future.
Idaho District 4: a 40 per cent materials saving
Charged with maintaining more than 4,940 centreline miles of highway, the Idaho Transportation Department (ITD) has invested around $5 million in a state-wide RWIS network consisting of 27 upgraded existing stations and 48 new RWIS sites that include 39 new Vaisala non-invasive solutions.
The resulting benefits have been substantial, as illustrated by ITD's District 4, which covers south central Idaho and includes 930 centreline miles of road over terrain that ranges from desert to mountain summits over 8,000 ft. The region experiences all kinds of winter weather, from mild frost and black ice to high winds, fast-changing temperatures and severe storms that can see several feet of snow fall overnight.
In addition to allowing a much more proactive operations strategy to be adopted, there have also been significant cost savings.
In 2005-2006, District 4 experienced 54 storm events. The next year, it started using RWIS data to change how and when roads were treated. Material costs were reduced by 10 per cent despite rising product prices and an almost equal number of snow events.
In 2007-2008, there were 73 storm events (35 per cent more) and certain product suppliers raised their prices by about 50 per cent. District 4 was still able to reduce material costs by another 30 per cent by using RWIS data to optimise operations.
Next steps in decision-making
Vaisala's Road Weather Decision Support System (RWDSS) has its roots in the prototype Maintenance Decision Support System (MDSS) which was developed with support from the US
The company will begin offering RWDSS in the third quarter of 2009.
