Winter: the joys of skiing on the slopes and slaloming between traffic jams
If winter is the joy of skiers, snow, frost and ice are also causing deterioration in traffic conditions. To secure the French national road network, which represents 950,000 kilometers of various roads, huge human and material resources are deployed. It must be underlined, the road network is with no doubt, a pillar of our economy.
Winter road maintenance is precisely the means of maintaining and restoring traffic conditions to a satisfactory level, from the point of view of safety and fluidity, in the use of the road. It is usually triggered from November to March and its effectiveness determines the continuity of economic activities during the winter season.
The State (national roads), the road authorities of the general councils (departmental roads), the concessionaires companies (motorway network) and the municipalities and communities of communes (communal network) organize a complex and rigorous 24/7 coordination.
It engages thousands of agents and equipment, ready to intervene a distance equivalent to about 24 times the turn of the earth!
Actions tailored to each climatic contingency
Road maintenance is considered from two angles.
“Healing”, by scraping from snow or ice, only used when the use of spreaders is not sufficiently effective in relation to the reactivity expected by the users for ” a reliable road network “.
The “preventive”, to avoid a slippery pavement by spreading salt (in brine or grain) is carried out before the appearance of ice or snow and represents the majority of interventions in winter road maintenance so that ice / or snow have as little grip as possible.
According to Planetoscope estimates, between 750,000 and 1,5 million tons of salt per year are dumped on roads in France to clear snow or melt the ice.
To maintain the circulation conditions and better preserve the environment by limiting the use of salt and other derivatives, the watchword is therefore: Anticipation.
The chain of collection and reporting of measures and information related to climate change on the road network thus represents a strategic link in decision-making support.
Measuring, monitoring, anticipating
Today, meteorological monitoring from satellites and radars, and prediction based on extremely complex models, offer maps displaying real-time data and images and forecasting scenarios essential for monitoring traffic conditions. Not sufficiently localized or precise enough to measure the impact of local variations, they are still incomplete, and require experience and field knowledge to be interpreted in a relevant way.
With the advent of the Internet of objects, information and communication technologies offer to provide an advanced Road Weather Information System (RWIS) by meshing a wide territory, in an extremely fine way, to measure continuously, to monitor in real time and anticipate.
As in the GrizzLY system in Lyon, it is possible to place miniature, wireless, energy-autonomous sensors at strategic points for continuous measurement of the pavement temperature and the humidity of the air. Operators access this data via the web and follow in real time the evolution of temperature and humidity curves, to monitor the “dew point” also called “frost point”.
The real-time report of these precisely localized data makes it possible to supplement the Météo-France (Public agency for weather forecasts) forecasts to react quickly to very localized phenomena. The reliability, accuracy and immediacy of the information obtained through these low-intrusive, inexpensive systems provide agility that limits resource consumption.
The objective is to optimize the use of human and material resources, while limiting the consumption of salt for a greater control of the costs of this specific organization. In addition to reducing salting operations, which is beneficial to the environment and to the winter viability budget, the limitation of the use of salt spreaders also contributes to maintain a smooth traffic.
This small video report speaks volumes: https://vimeo.com/122002752
Acting as close as possible to reality, to be efficient
The cost of winter road maintenance varies depending on the severity of the winters. The Interdepartmental Directorate of Eastern Roads in France shares that for the winter of 2015/2016 the cost was € 4.7 million (excluding personnel costs), salt consumption at 14,200 tons and has mobilized 142 gears and 645 people between the ground, the organization and the steering of operations.
At the same time, knowing the complexity of decision-making in road winter service, the value of wireless monitoring systems based on miniature sensors is directly measured by the enhanced performance of the RWIS.
Anticipating means being able to define which salts or derivatives to spread. This will usually be sodium chloride up to -6 ° C or -8 ° C, calcium chloride will be used for lower temperatures.
Spreading at the ideal moment is tantamount to intervening from the moment when salting acts effectively against the formation of the ice, so not too early, and as long as it is useful, that is to say, not too late.
The ability to continuously measure finely, locally and process this information in real time makes the winter road maintenance mission more effective.
Under these new conditions, it is easier to:
- Enhance road safety,
- Preserve economic activity,
- Reduce CO2 emissions,
- Optimize the use of human and material resources,
- Limit salt spreading operations to preserve our environment.
Given all these advantages, it is not surprising that the Observatory of Transport Policies and Strategies in Europe has identified these advanced RWIS systems as notable innovations in transport management.