**2. Materials and methods**

Typical winter road maintenance activity is the mechanical removal of snow accompanied by deicing with chemicals or traction enhancement with abrasives. To conduct such activities, vehicles equipped with liquid and solid spreaders, and plows are required. Plowing and/or spreading of deicer are associated with the consumption of fuel (vehicles are typically run on diesel) and deicers, which are most commonly salt and sand [6, 9]. Other deicers can also be used, such as calcium chloride, magnesium chloride, agro-based products, acetates, formates, glycols, and succinates [9].

Special Road-Weather Information Systems (RWIS) have been designed for WRM agencies to help them evaluating road conditions in cold climates in a way, that they can optimize the timing of salting and plowing activities [10]. By using Road-Weather Information System, the WRM agency obtains reliable information about the timing of snowfall on a particular section of the road and about the bonding of the snow with the road surface. The system is based on physical, energy-balance model to predict road conditions such as dry, wet, snowy, icy, for every hour and for 12 hours in advance. The forecast is high-resolution in time (forecast per every hour) and space (forecast for every km of road section).

#### **2.1 Scenarios**

### *2.1.1 Baseline WRM operation scenario*

WRM agency does not use Road-Weather Information System and for this reason, the activities related with road maintenance (gritting with salt and plowing) begin

only when the snow is already bonding with the road surface. During a long-lasting snowstorm, the WRM vehicle must pass the road section several times. The vehicle conducts gritting and plowing simultaneously. Fuel consumption of the WRM vehicle is increased because the vehicle drives in demanding weather conditions (when the snow is already bonding with the road surface). Moreover, the use of a plow has a direct impact on the relatively higher fuel consumption of the WRM vehicle. Other vehicles (passenger cars, trucks) passing the road section during snowstorms must adapt their driving to the snow conditions on the road. Fuel consumption of vehicles driving on the road is higher, which means that associated emissions are also higher. In general, snow and ice coverage on a road surface increase the fuel consumption of vehicles. The wheels can slip on the road, wasting energy as they have reduced grip, while driving speeds are significantly lower than normal [11]. For the purpose of this study, it was assumed that the corresponding increase in fuel consumption is 10, 20, and 30% respectively. This assumption is supported by literature data [12–14].

## *2.1.2 Preventive WRM operation scenario*

Taking into account information obtained by Road-Weather Information System, the WRM agency can perform a preventive operation and start gritting with salt just before the beginning of the snowfall and its bonding with the road surface. The effectiveness of preventive activity (e.g., gritting with salt or some other anti-icing agent) is strongly linked to precise timing of the activity. The WRM vehicle conducts the preventive gritting with an anti-icing agent (salt) still on a dry road, while subsequent gritting operations are conducted during snowfall, on a wet, but still snow and ice-free road (meaning that plowing is not needed). The number of subsequent operations depends on the duration of weather event (e.g., snowstorm). The first preventive and subsequent gritting operations result in snow melting, so there is no snow accumulation on the road surface. In such conditions, the WRM agency uses up to 40% less salt than in baseline WRM operation scenario. Other vehicles passing the road section during the snowstorm event may drive at normal speeds, adapted to conditions of the wet road surface. Vehicles do not consume more fuel than usual. If so, emissions related to exhaust gases do not increase compared to normal weather conditions.
