Climate change poses challenges for road transport


Road transport is the most important form of transport in Finland, and traffic volumes are continuously increasing. Road transport is relatively vulnerable to the effects of climate change. For example, the increasing likelihood of extreme weather events increases the costs associated with road maintenance. Some of the effects of climate change are nevertheless favourable to road transport, such as the decreasing risk of frost damage to roads. 

The role of road transport in society

Road transport is by far the most important form of transport in Finland. In 2009, road transport accounted for 68 percent of goods transport and 93 percent of passenger transport. Private cars are easily the most popular form of passenger transport, and it accounted for 82 percent of all passenger transport in 2009. A considerable percentage of goods transported by road were timber products. [1]

The number of cars relative to total population in Finland is consistent with the European average. Road transport is concentrated on the trunk roads of Southern Finland, where traffic jams resulting from commuter traffic are an almost daily occurrence. Almost all road transport – approximately 96 percent – takes place on paved and tarmac roads, while gravel roads only account for four percent of all road transport. [1] Traffic volumes on public roads in Finland are forecasted to increase by 24 percent between 2002 and 2030. The concentration of population in towns and cities is expected to increase the use of trunk roads at the expense of other roads. Local and private roads will nevertheless remain important in sparsely populated areas. [2]

Sensitivity of road transport to weather and climatic factors

There are three major weather factors that affect road transport: temperature, rain, and wind. Each of these has many implications on road transport and road maintenance. Low and high temperatures, rainstorms, increasing average rainfall, and violent winds can cause disruptions in road transport, damage road infrastructure, and complicate road maintenance. [3]

Sometimes weather conditions have direct implications on road maintenance and repairs. For example, roads need to be cleared of snow whenever snow falls, and the volume of snowfall therefore has a direct effect on the cost of snow removal. The level of road maintenance required also depends on many other factors such as the materials used to build roads, the numbers of road users, and earlier repairs. [4]

Climate change affects winter road maintenance

Climate change has implications on the need for anti-icing and de-icing as well as other aspects of winter road maintenance. Increasingly mild winters are expected to mean fewer days of sub-zero temperatures in Southern Finland. This reduces the need for de-icing and the use of salt on roads in the southern parts of the country. However, the need for anti-icing is likely to increase in Central Finland and Northern Finland, and the focus of winter road maintenance will shift further north. [4]

Milder winters are likely to mean less ground frost and therefore a lower risk of frost damage to roads. Higher temperatures and the fact that rainfall is likely to increase at the expense of snowfall may nevertheless increase wear on road surfaces, because snowless and wet road surfaces are more vulnerable to wear caused by studded winter tyres. Wear and rutting is likely to increase considerably especially on busy roads, and especially in Southern and Western Finland. The average rate of rutting on roads in the southern and western parts of the country has increased by between 30 and 45 percent in the last five years. Some of this is nevertheless attributable to increasing traffic volumes. In Eastern Finland and Lapland, the rate of rutting has remained at previous levels or even dropped. [4]

The likelihood of freezing rain, which creates treacherous road conditions, is expected to decrease in Finland in the future, by a few days even by 2040. However, freezing rain is expected to become slightly more common in the northernmost parts of Finland, as temperatures around zero degrees become more common. [5] Short-lived snowstorms, when a lot of snow falls at once, are likely to increase with climate change. Heavy snowfall causes disruptions and delays in traffic. All in all, the need for snow removal is likely to remain relatively unchanged or to decrease, because the period of snow cover will become shorter. [4]

Figure 1. Traffic on the outermost of the three ring roads around Helsinki.

© Raili Malinen

Milder winter temperatures may affect the likelihood of ground frost in two ways. On one hand, higher average temperatures limit frost formation, and frost may not penetrate as deep into the ground as before. On the other hand, the thinner snowpack may counteract this: Frost penetrates deeper into the ground if temperatures drop below freezing when there is no protective layer of snow. The likelihood of frost is nevertheless expected to decrease on the whole, and this has negative implications on forestry and timber transport, for example, as the ground will no longer be able to support the weight of forest machinery as well as before. [2] [3] [4]

The winters of 2006–2007 and 2007–2008 were considerably milder than average in Finland. Winter maintenance statistics compiled during these years provide valuable information about the kinds of effects that milder winters may have on winter road maintenance. Snow removal was required less often in Southern and Central Finland and on the west coast during the milder winters, while other parts of the country experienced no change. The winters between 2006 and 2008 were also unusual in terms of anti-icing, because more sand was used on roads than during the previous winters. The need for sanding was substantially higher than during previous years especially in Lapland, on the north coast, and in Eastern Finland. The use of salt decreased or remained unchanged on the west and south coasts, while considerably more salt had to be used inland and in Lapland during the winter of 2007–2008. [4]

Climate change also affects the maintenance of ice roads and shortens the period during which they can be used in the winter. This is why public ice roads may no longer be maintained in the future. This has already happened in places where a ferry service operates throughout the winter. Discontinuing maintenance on public ice roads lowers the cost of winter road maintenance but increases journey times and therefore the costs incurred by road users. [4]

Road maintenance costs are rising

Climate change is estimated to increase the total costs arising from road maintenance to some extent. No sudden rises are nevertheless expected and instead the changes in costs are likely to happen over a long period of time, perhaps over several decades. Climate change may also help to lower road maintenance costs in some areas, for example, by decreasing the need for anti-icing, de-icing, and snow removal in Southern Finland. [4]

The number of days when road surfaces are not protected by snow is likely to increase during warm and rainy winters, which will increase wear and road maintenance costs. The longer period when the ground is not frozen will increase maintenance costs on gravel roads. Gravel roads currently also require winter maintenance along the southwest coast, and this trend is likely to spread to other parts of Southern Finland. Repairs carried out on gravel roads in preparation for the winter have also been complicated by the late onset of winter in Central Finland. [4]

Figure 2. A road under flood water.

© Riku Lumiaro

Climate change is expected to increase both the overall volume of rainfall and the likelihood of rainstorms, which causes problems on roads. Rising groundwater levels may weaken roads in places, shorten their useful lives, and increase the risk of damage to road infrastructure. Rainstorms are likely to increase erosion on roadsides and around bridge supports. The capacity of drainage wells and tunnels and bridge arches may prove inadequate in the face of the increasing frequency of rainstorms and the resulting floods. The increasing use of salt and rising average temperatures accelerate corrosion in bridges, and higher flow rates increase wear on underwater structures. These factors also contribute to the rising costs of maintaining roads and bridges. [3] [4]

Climate change and road traffic safety

Scientists have found that the rarer challenging weather conditions are in a certain area, the higher the risk of accidents. The element of surprise increases the likelihood of traffic accidents. With milder winters, roads are likely to be free of snow for longer and longer periods of time, which improves traffic safety. On the other hand, icy conditions resulting from temperatures close to zero degrees and freezing road surfaces are likely to become more common in Central and Northern Finland, making roads more treacherous. The fact that snowy and icy conditions are becoming increasingly rare in Southern Finland creates an element of surprise and therefore increases the risk of accidents. Studies show that the risk of accidents resulting from snow and ice is higher in Southern Finland than in Northern Finland for this reason. Accident statistics compiled between 2004 and 2006 indicate that the risk of accidents is approximately four times higher in icy and snowy conditions than when road surfaces are free of ice and snow. [6]

Lighting also affects the likelihood of accidents. Snow cover increases the efficiency of street lights by approximately 30 percent compared to a black road surface. The increasing likelihood of dark, wet, and snowless conditions in early winter will increase the need for street lighting in the future. The introduction of modern, energy-efficient lighting technology that adapts to traffic volumes may nevertheless decrease the energy required for lighting. Street lighting has been found to decrease the number of accidents taking place during the hours of darkness by approximately 10 percent. [4]

Climate change may also affect the number of accidents caused by deer on the roads. The Eurasian elk, the European roe deer, and the white-tailed deer are all likely to benefit from decreasing snow cover during increasingly mild winters, because the plants that they feed on will be more readily available and the animals are able to move more easily. With climate change, the increasing numbers of deer may also increase the risk of accidents involving deer on the roads. [2]

Preparing roads for the effects of climate change

Different kinds of warning systems and weather forecasts about treacherous road conditions and the risk of flooding are vital for preparing road transport for the effects of climate change. Examples include the weather services provided by the Finnish Transport Agency, the Finnish Meteorological Institute, and Destia, which cover a wide range of information targeted at road users and maintenance personnel.

Experience has shown that contingency planning is vital for controlling floods. Other ways to prepare for potential problems include increasing cooperation between government agencies and maintaining preparedness for emergencies in the form of human resources, equipment, and materials. The risk of flood damage to road infrastructure can be controlled by building floodbanks, by improving drainage systems, and by reinforcing structures that are susceptible to high flow rates, such as bridge supports and drainage tunnels. Design criteria for new road structures and for repairs carried out on existing roads need to factor in future flood heights, and pump systems may need to be introduced for improving drainage in underpasses. [2] [3] [7]