ANALYSIS AND EVALUATION OF THE EFFECT OF STUDDED TYRES ON ROAD PAVEMENT AND ENVIRONMENT (III)

In the economic evaluation of studded tyres their benefi t and damage to the public was analyzed. Such aspects as the price of studded tyres, their eff ect on braking distance, fuel costs, road pavement, pavement marking, initiation of particulate mater and the increase in noise emisions were compared and analyzed. Based on the inquiry of tyre sellers and executed calculations, it was determined that in Lithuania, in winter season about 15% of passenger cars use winter tyres with studs, therefore due to the reduced number of road accidents (reduced number of people killed and injured) the public receives the benefi t of 1.81 mln EUR. However, due to the more expensive tyres, increased fuel consumption, damages to horizontal pavement marking, negative impact of particulate matter on human health the public incur considerably higher losses amounting even to 38.43–39.07 mln EUR.


Introduction
In the last several years a number of passenger cars using studded winter tyres on Lithuanian roads have been gradually decreasing. Th is fact is also confi rmed by the tyre sellers. Based on their data, 5-7 years ago the sales of studded tyres for passenger cars made 40-60%, whereas, in the last winter season of 2008 the sales of studded tyres (and of those prepared for studding) made only 4-8% of the total sales of winter tyres. Such a low percent of the sales of studded tyres was infl uenced by the newly accepted legal acts providing for a future prohibition of the use of studded tyres on Lithuanian roads. Besides, the car owners who travel or plan to travel by car to the European Union (EU) member-states (starting with Poland and further to the south) choose to buy non-studded winter tyres since the use of studded tyres in those countries is prohibited.
Based on the above statistical data, it was assumed in the calculations that in winter 15% of passenger cars use studded winter tyres. Th us, in the economic evaluation of studded tyres the analysis of their benefi t and damage was carried out, i.e. the following aspects were analyzed and compared: the price of studded tyres; their eff ect on braking distance, fuel costs, road pavement, pavement marking, initiation of particulate matter (PM) and on the increase in noise emissions Vaiškūnaitė et al. 2009).

Accident losses caused by passenger cars using nonstudded and studded tyres
Based on data of the Association of Companies for Road Vehicle State Technical Inspection Transeksta, according to the number of road vehicles presented for the initial technical inspection Lithuania has ~1100000 of the used passenger cars use, of which 15% (~165 000 units) are equipped with winter tyres having studs. Th e driver, having acquired winter tyres, uses them on the average for 4 years. Th us, the additional costs for the Lithuanian drivers (between studded and non-studded winter tyres) will average to 1.91-2.39 mln EUR/year: (1) where K ΔP -additional annual costs for the Lithuanian drivers having acq uired studded winter tyres, mln EUR/year; ΔK ZD -diff erence between the prices of studded and nonstudded winter tyres, EUR; T ZD -number of passenger cars equipped with studded winter tyres, units; P T -average service life of studded winter tyres, years.
If a theoretical assumption is made that the use of studded tyres in winter is obligatory, the additional costs for the drivers (K ΔPT ) (between studded and non-studded winter tyres) would amount to 12.74-15.93 mln EUR/year: (2) Many of world-wide investigations to determine a percentage diff erence in road accidents using studded and non-studded winter tyres showed that when using passenger cars with studded tyres on snowy or icy road pavement the accident risk is reduced by 5%, on dry and wet pavement -by 2%. When using passenger cars with studded tyres under various (all) traffi c conditions the accident risk is reduced by up to 4%.
Having calculated the average of accidents of 2005-2008 winter seasons and the distribution of accident victims according to pavement condition, it could be stated that in this period the average number of accidents was 2329 where 267 people were killed and 2757 were injured. Since no data is available on the type of winter tyres (studded or non-studded), it was assumed in the calculations that 15% of accident-involved passenger cars were using studded tyres and 85% -non-studded tyres. Correspondingly, accidents were calculated where the passenger cars with studded tyres were damaged. In the calculations the eff ect of studded tyres on the accident risk was taken into consideration (i.e. the accident risk is reduced by 4% on the average).
It was calculated that 15% of the Lithuanian road users used studded tyres in winter, therefore, on the average 1.6 lives were saved and 16.54 less people were injured every year compared to the case if all passenger cars had used non-studded tyres. If accident costs are multiplied by these reductions it is obtained that due to the use of studded tyres in Lithuania the damage caused by road accidents is reduced by 1.81 mln EUR/year on the average. In the further analysis of this research, when calculating damage caused by road accidents, the damage (theoretical) caused by vehicles with studded tyres (from 1 November to 1 April) was compared to that with non-studded tyres. Defi nitely, this calculation is more theoretical since in this case a legal act would be necessary prohibiting the use of winter non-studded tyres. Accident-caused damage when using passenger cars with non-studded and studded tyres is given in Fig. 1.
Th ough, when using passenger cars with studded tyres under various traffi c conditions, the risk of accidents is reduced only by 4%, a number of people killed and injured on the Lithuanian roads in the recent 4 years shows that the average theoretical diff erence in the use of passenger cars with non-studded and studded tyres makes 12.86 mln EUR per year (Elvik, Vaa 2004;Kapski et al. 2008;Tampère et al. 2009).

Th e eff ect of winter tyres on fuel costs
Vehicle fuel costs are increased by 15% on icy and snowy road pavements compared to dry roads. It was determined in the foreign researches that when using a passenger car with studded tyres the fuel costs increase from 1.2% to 2% compared to non-studded tyres (Scheibe 2002;Zubeck et al. 2004) and according to some sources -even from 4% to 8%. Fuel costs in winter depend not only on the type of tyres (studded or non-studded) but also on road maintenance, driving speed, mode of driving, etc. Th e Vehicle Operating Costs (VehOC's) of a passenger car (EUR/1000 veh-km) under diff erent pavement roughness in the year 2008 are given in Fig. 2. With the help of Highway Development and Management model-4 (HDM-4) the VehOC's under diff erent pavement roughness were calculated. In the model the fuel costs of passenger cars make 30-40% of the total transport expenditures. In the calculations of this research it was assumed that the fuel costs of a passenger car make 35% of its total operating costs.
Th e annual average daily traffi c (AADT) and its composition on the roads of diff erent groups by the different class of vehicles in 2008 are given in Table 1. Th e AADT on all the roads of national signifi cance is 1414 vehicles per day, of which 1087 are passenger cars. Th e AADT of passenger cars in the diff erent group of roads (Accumulation and renewal of traffi c data of the roads of national signifi cance, 2008) is given in Fig. 3.
Th e annual mileage by vehicles is the total amount of vehicle kilometres per year on the considered road or its section. Th is index refl ects the size of the national vehicle fl eet and the volume of its use. Th e annual mileage AM is calculated by the Eq (3): ( 3) where AM -the annual mileage of the vehicle kilometres per year, veh-km/year; AADT -annual average daily traffi c of the road section per day, vpd; L-length of the road section, km.
Th e annual mileage by vehicles per a group of roads is calculated as the sum of annual mileage on the separate sections of this group of roads AM. Based on the previously analyzed statistical traffi c data and the length of Lithuanian roads of national signifi cance, the annual mileage was calculated for the main and national roads in 2006.
Having made the analysis of traffi c volume of the roads of national signifi cance, it was calculated that from 1 November to 1 April the annual mileage by passenger cars makes 35.80% of the total annual mileage.
Based on the statistical traffi c data, traffi c composition and the calculated annual mileage, it is possible to calculate how many kilometres in the diff erent group of roads are travelled by passenger cars per year, how many kilometres are travelled in winter and how many kilometres are travelled by passenger cars with studded tyres.
In the beginning of 2009 the average pavement roughness on the main roads was 2.27 m/km, on national roads -3.16 m/km, and on regional roads -4.50 m/km. Based on the calculated annual mileage by passenger cars with studded tyres in winter (Fig. 5), the average pavement roughness and the diff erence in fuel costs under the existing pavement roughness (Fig. 2), it is possible to calculate what is the increase in the annual fuel costs for the road users travelling by passenger cars with studded tyres: (4) where C F -the annual fuel costs for the road users travelling by passenger cars with studded tyres, mln EUR/year; AM PC -the annual mileage by passenger cars with studded tyres in winter per year, veh-km/year; RV PRFC -the ratio between values of the average pavement roughness and of the diff erence in fuel costs under the existing pavement roughness per kilometer, EUR/km.   (Gustafsson et al. 2008;Ketzel et al. 2007;Kupiainen 2007;Schmit, Schlender 2003;Vallius 2005).
Taking into consideration the impact of one of vehicle-generated pollution sources, i.e. studded tyres, on the environment, the analysis was focused only on particulate matter. Particulate matter is a mixture of particles and liquid droplets (aerosols) suspended in the ambient air and consisting of diff erent components -acids, sulphates, nitrates, metals, organic compounds, soil particles, dust, smut. In winter road vehicles, especially those using studded tyres, cause also a secondary pollution with particulate matter. Th is means that the studded winter tyres destroy road pavement, lift into the ambient air the remnants of destroyed pavement, the spread sand and salt mixture and uncollected mud, and when using such tyres on "bare" road pavement (without ice or snow) -fi ne and very dangerous micro elements initiated during traction. Th e Swedish researchers have determined that a passenger car with studded tyres having travelled 1 km "mills out" about 5-12 g of asphalt particles on a rural road and about 2-5 g on a city street. In cities the wear of asphalt pavements is slower due to a lower driving speed (Hääl et al. 2008;Norman, Johansson 2006;Räisänen et al. 2005).
It was assumed in the calculations that one vehicle with studded tyres having travelled one kilometre on a rural road "mills out" 2 g of asphalt particles.
When assessing the eff ect of studded tyres on the initiation of particulate mater it was assumed that 15% of the total number of passenger cars in winter (i.e. 5 months per year) uses studded tyres. Having made the analysis of traffi c volume on the roads of national signifi cance it was calculated that from 1 November to 1 April the passenger cars travel 35.8% on he average of the total annual mileage. Based on the calculated annual mileage by passenger cars with studded tyres per year (Fig. 6) it is possible to calculate how much particulate matter is "milled out" from the road pavement by the studs of winter tyres on the roads of national signifi cance: It is possible to calculate by the Eq (4)  It was determined that when using passenger cars with studded tyres their fuel costs are increased by 4%, the road users (owners or managers of vehicles), solely on the roads of national signifi cance, incur the additional fuel costs of 1.68 mln EUR/year.
Th eoretical damage to the road users due to the increased fuel costs, if all passenger cars had to obligatory use studded tyres in winter, solely on the roads of national signifi cance, would make 11.24 mln EUR/year of additional fuel costs. It is possible to calculate: (5) where C TF -the annual fuel costs for the road users travelling by passenger cars with studded tyres (if all passenger cars had to obligatory use studded tyres in winter), mln EUR/year; AM TPC -the annual mileage by passenger cars with studded tyres in winter per year (if all passenger cars had to obligatory use studded tyres in winter, from 1 November to 1 April), veh-km/year; RV PRFC -the ratio between values of the average pavement roughness and of the diff erence in fuel costs under the existing pavement roughness per kilometer, EUR/km.
It is possible to calculate by the Eq (5) where Q T -the total quantity of asphalt particles, which "milled out" from the road pavement passenger cars with studded tyres per year on the roads of national signifi cance, t/year; AM PC -the annual mileage by passenger cars with studded tyres in winter per year, veh-km/year; Q G -the quantity of asphalt particles, which "mills out" from the road pavement one vehicle with studded tyres having travelled one kilometre, g/km. It is possible to calculate by the Eq (6)  Based on a number of asphalt particles "milled out" by the studs of winter tyres from the asphalt pavement on main, national and regional roads and the cost of particulate matter pollution in a rural territory (Fig. 6), the damage from the studs was calculated: (7) where D TS -the damage of the tyres studs on the roads national signifi cance per year, mln EUR/year; Q T -the total quantity of asphalt particles, which "milled out" from the road pavement passenger cars with studded tyres per year on the roads of national signifi cance, t/year; C RT -the cost of particulate matter pollution in a rural territory, EUR/t.
It is possible to calculate by the Eq (7) In Lithuania, in a period of winter season almost 15% of passenger cars use studded winter tyres which exhaust into the ambient air particulate matter and negatively aff ect human health. It was determined that this damage, solely on the roads of national signifi cance, amounts to 33.96 mln EUR/year.
Taking into consideration the use of studded tyres on the local roads (also in a residential area, especially in city streets), damage to the public would be increased even more. Due to the lack of statistical data on a number of kilometres travelled on these roads, damage to the public due to the increased particulate matter was not assessed.
For this purpose a theoretical damage was calculated which would be caused by particulate matter if all passenger cars in a winter season (from 1 November to 1 April) had to obligatory use only studded tyres. A theoretical amount of asphalt particles "milled out" from the pavement of the roads of national signifi cance, if all passenger cars used only studded tyres in winter, would amount to 6037.00 t/year: (8) where T PM -the theoretical damage of particulate matter from the tyres studs on the roads national signifi cance per year (if all passenger cars in a winter season (from 1 November to 1 April) had to obligatory use only studded tyres), t/year; AM TPC -the annual mileage by passenger cars with studded tyres in winter per year (if all passenger cars had to obligatory use studded tyres in winter, from 1 November to 1 April), veh-km/year; Q G -the quantity of asphalt particles, which "mills out" from the road pavement one vehicle with studded tyres having travelled one kilometre, g/km.
It is possible to calculate by the Eq (8): On main roads: t/year; On national roads: t/year; On regional roads: t/year; Total: 6037.00 t/year. A theoretical damage to the public due to particulate matter "milled out" and exhaust into the ambient air would amount to 226.42 mln EUR.
Noise is a disorderly mixture of sound waves of various strength and frequency, unusual to human ear and causing unpleasant sensations. Noise damages hearing, irritates the central nervous system, changes human character and behaviour, induce crudity and aggression of an individual. All over the world road transport is recognised as the main source of noise.
When a studded tyre rolls over the road surface the increased tyre vibration causes noise. A higher traction of studded tyres and road pavement, compared to that of non-studded tyres, increases noise emission by 3-5 dBA (Kropp et al. 2007;Peeters, Blokland 2007).
In Sweden, when the use of studded tyres was reduced by 20% the noise emissions decreased by 1.0-1.5 dBA. In Lithuania, in the last two winter seasons studded tyres were used by about 15% of all passenger cars. Based on the Swedish research data it could be stated that having prohibited the use of studded tyres in Lithuania the general noise level would be decreased by 0.75-1.13 dBA. Th e specialists have calculated the damage to the human health caused by the equivalent noise level in a day. Th e cost of noise emissions are given in Fig. 7 (Environmental Impact Assessment of the Reconstruction of the Road A5 Kaunas-Marijampolė-Suwalki 22.0-56.5 km section). Th e cost of noise emissions shows that with the increased equivalent noise level only by 5 dBA the damage to the human health has been signifi cantly increasing. It is almost impossible to determine the noise-caused damage to the public, since in the diff erent noise diapasons the damage to the human health varies unevenly, besides, people use to live at a diff erent distance from the main transport arteries and no exact data is available on what is a number of residents living close to them.

Th e eff ect of studded tyres on road pavement marking
Studded tyres intensively damage road pavement surface. Th e wear of road pavement is considerably larger compared to the use of the other type of tyres. At present horizontal marking of Lithuanian roads is carried out with paint or polymer materials. Th e service life and warranty of horizontal marking are dependent on the designation of lines and the materials used. Using polymer materials the marking can have a thin layer or a full thickness. When a continuous edge line is marked with paint the service life of marking is two years. When the centre road line is marked with paint and other horizontal marking is carried out the service life is one year. When horizontal marking is made by polymer materials the service life of the marking is twice as long, i.e. when using polymer materials the service life of full-thickness marking is four years, while the service life of the above mentioned thin-layer marking materials -two years. Certainly, the use of polymer materials for horizontal marking generates higher costs. Comparison of the costs is given in Fig. 8. Studded tyres cause the wear of all types of horizontal marking at pedestrian crossings, of continuous and discontinuous marking lines on the carriageway. In a day time horizontal marking can visually look as of suffi ciently good quality, though in a dark period of the day it does not serve the main function, i.e. to refl ect light, since a specifi c density of light in darkness is too low. Th e main reason -the marking surface is polluted with unrefl ecting materials. Horizontal marking is mostly damaged by studded tyres when it is polluted with the "milled out" bitumen particles from asphalt pavement in winter and becomes poorly visible in a dark time of the day. When a marking line is passed by studded tyres the studs stick into the line and leave small depressions with the remnants of bitumen particles.
We did not succeed to fi nd any accurate scientifi c investigations on how much the service life of horizontal marking would be extended if the vehicles used no studded tyres. However, all the road specialists unanimously admit that studded tyres reduce the durability of horizontal marking. A very cautious forecast was assumed in the calculations that with the use of studded tyres the wear of horizontal marking is 10% faster. Correspondingly, it could be apparently stated that in a year due to the use of studded tyres the wear of horizontal marking is faster and the public looses ~10% of funds allocated to the marking. In the last two years 8.69-10.14 mln EUR was allocated each year to the renovation of marking on the roads of national signifi cance. Besides, additional horizontal marking was implemented on the repaired and reconstructed road sections.
Based on the above, it could be stated that due to a faster wear of horizontal marking the public looses 0.87-1.01 mln EUR every year.

Economic evaluation of winter tyres (studded and non-studded)
Having made a comparative cost-benefi t analysis, a comparison of studded and non-studded winter tyres and their benefi t (additional costs) for the public, it was determined that it is more cost-eff ective for the road users to use nonstudded tyres. A comparative cost-benefi t analysis is given in Fig. 9 and Table 2 where positive and negative factors (pluses and minuses) for the use of studded and non-studded winter tyres are described.
In winter almost 15% of the road users in Lithuania use studded tyres on their passenger cars, therefore due to the reduced number of road accidents (reduced number of people killed and injured) the public receives the benefi t of 1.81 mln EUR. However, due to the more expensive tyres, increased fuel consumption, damages to horizontal pavement marking, negative impact of particulate matter on human health the public incur considerably higher losses amounting even to 38.43-39.07 mln EUR (Baltrėnas et al. 2007;Lama et al. 2007;Radziszewski 2007;Ziari et al. 2007;Zubeck et al. 2004).

Conclusions
Based on the inquiry of tyre sellers it was determined that in Lithuania, in winter season about 15% of passenger cars use winter tyres with studs.
It was identifi ed that additional costs for the drivers (between studded and non-studded winter tyres) will amount to 1.91-2.39 mln EUR/year on average.
Taking into consideration a number of people killed and injured during road accidents on the roads of Lithuania in 2005-2008, it was calculated that due to the use of studded tyres the accident-caused damage is reduced by 1.81 mln EUR/year on average.
When using passenger cars, equipped with studded tyres, the fuel consumption of these cars is increased by 4%, thus, the road users (owners or managers of cars) solely on the roads of national signifi cance incur the additional fuel costs of 1.68 mln EUR/year. When using studded winter tyres the public incurs more damage than benefi t. Fig. 9. Economic evaluation of winter tyres (studded and nonstudded) (Aadditional costs for the drivers due to studded tyres; Badditional costs for the drivers due to non-studded tyres; Cdamage due to road accidents; Deff ect of tyres on fuel costs; Eeff ect of studded tyres on the initiation of particulate matter; Fdamage due to tyre-generated noise; Geff ect of tyres on pavement marking; H -total damage) In Lithuania, in a period of winter season about 15% of passenger cars use studded winter tyres which lift particulate matter and negatively aff ect human health. Th is damage, solely on the roads of national signifi cance, amounts to 33.96 mln EUR/year. It was determined that due to the use of studded tyres and faster wear of horizontal marking the public incur 0.87-1.01 mln EUR of additional costs every year.
In winter about 15% of the road users in Lithuania use studded tyres on their passenger cars, therefore due to the reduced number of road accidents (reduced number of people killed and injured) the public receives the benefi t of 1.81 mln EUR. However, due to the more expensive tyres, increased fuel consumption, damages to horizontal pavement marking, negative impact of particulate matter on human health the public incur considerably higher losses amounting even to 38.43-39.07 mln EUR.