The authors would like to acknowledge the Scientific Research Program Funded by the Shaanxi Provincial Education Department (Program No. 21JK0908).

1. Preparation of the equipment
<ol>
	<li>BPT
	<ol>
		<li>Ensure that the BPT (Figure 1) is within its service life and that the surface is clean and undamaged. 
		NOTE: The components of the BPT are the base, leveling spiral, leveling bubble, pointer, pendulum, lifting spiral, fastening spiral, handle, and dial.</li>
	</ol>
	</li>
	<li>Asphalt slabs
	<ol>
		<li>Ensure that the asphalt mixture sample size used for the experiment is 30 cm x 30 cm x 5 cm.</li>
	</ol>
	<...

<ol>
	<li>Rajamani, R., Piyabongkarn, N., Lew, J., Yi, K., Phanomchoeng, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tire-road+riction-coefficient+estimation.">Tire-road riction-coefficient estimation.</a> IEEE Control Systems Magazine. 30 (4), 54-69 (2010).</li><li>Wallman, C. -. G., &#197;str&#246;m, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Friction+measurement+methods+and+the+correlation+between+road+friction+and+traffic+safety:+A+literature+review.">Friction measurement methods and the correlation between road friction and traffic safety: A literature review.</a> Swedish National Road and Transport Research Institute. , (2001).</li><li>Kuttesch, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantifying+the+relationship+between+skid+resistance+and+wet+weather+accidents+for+Virginia+data.">Quantifying the relationship between skid resistance and wet weather accidents for Virginia data.</a> Virginia Tech. , (2004).</li><li>Juga, I., Nurmi, P., Hippi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Statistical+modelling+of+wintertime+road+surface+friction.">Statistical modelling of wintertime road surface friction.</a> Meteorological Applications. 20 (3), 318-329 (2013).</li><li>Zhang, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+optimum+amount+of+road+deicing+salt+in+humid+areas.">The optimum amount of road deicing salt in humid areas.</a> Advances in Engineering Research. 153 (2017), 283-290 (2017).</li><li>Haavasoja, T., Pilli-Sihvola, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Friction+as+a+measure+of+slippery+road+surfaces.">Friction as a measure of slippery road surfaces.</a> Proceedings of 15th International Road Weather Conference. SIRWEC. , (2010).</li><li>Norrman, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Slipperiness+on+roads-an+expert+system+classification.">Slipperiness on roads-an expert system classification.</a> Meteorological Applications. 7 (1), 27-36 (2000).</li><li>Mayora, J. M. P., Pi&#241;a, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+assessment+of+the+skid+resistance+effect+on+traffic+safety+under+wet-pavement+conditions.">An assessment of the skid resistance effect on traffic safety under wet-pavement conditions.</a> Accident Analysis &amp; Prevention. 41 (4), 881-886 (2009).</li><li>Juga, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+snowfall+and+low+temperature+on+road+traffic+accident+rates+in+Souther.">The effect of snowfall and low temperature on road traffic accident rates in Souther.</a> Proceedings of 16th International Road Weather Conference. SIRWEC. , (2012).</li><li>Walu&#347;, K. J., Olszewski, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+tire-road+contact+under+winter+conditions.">Analysis of tire-road contact under winter conditions.</a> Proceedings of the World Congress on Engineering. WFEO and UNESCO. , (2011).</li><li>Salimi, S., Nassiri, S., Bayat, A., Halliday, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lateral+coefficient+of+friction+for+characterizing+winter+road+conditions.">Lateral coefficient of friction for characterizing winter road conditions.</a> Canadian Journal of Civil Engineering. 43 (1), 73-83 (2016).</li><li>Hunter, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reconstructing+collisions+involving+ice+and+slippery+surfaces.">Reconstructing collisions involving ice and slippery surfaces.</a> SAE Transactions. 102, 1425-1436 (1993).</li><li>Hayhoe, G., Shapley, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tire+force+generation+on+ice.">Tire force generation on ice.</a> Journal of Passenger Cars. 98 (6), 30-38 (1989).</li><li>Peng, X., Xie, Y., Guo, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+method+for+determining+tire+traction+on+ice.">A new method for determining tire traction on ice.</a> SAE 2000 Automotive Dynamics &amp; Stability Conference. , (2000).</li><li>Klapproth, C., Kessel, T., Wiese, K., Wies, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+advanced+viscous+model+for+rubber-ice-friction.">An advanced viscous model for rubber-ice-friction.</a> Tribology International. 99, 169-181 (2016).</li><li>Lahayne, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rubber+friction+on+ice:+experiments+and+modeling.">Rubber friction on ice: experiments and modeling.</a> Tribology Letters. 62 (2), 17 (2016).</li><li>Hippi, M., Juga, I., Nurmi, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+statistical+forecast+model+for+road+surface+friction.">A statistical forecast model for road surface friction.</a> Proceedings of 15th International Road Weather Conference. SIRWEC. , (2010).</li><li>Ivanovi&#263;, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+identification+of+dynamic+tire+friction+potential+on+ice+surfaces.">Experimental identification of dynamic tire friction potential on ice surfaces.</a> Vehicle System Dynamics. 44 (1), 93-103 (2006).</li><li>Gao, J., Zhang, Y., Du, Y., Li, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimization+of+the+tire+ice+traction+using+combined+Levenberg-Marquardt+(LM)+algorithm+and+neural+network.">Optimization of the tire ice traction using combined Levenberg-Marquardt (LM) algorithm and neural network.</a> Journal of the Brazilian Society of Mechanical Sciences and Engineering. 41, 40 (2019).</li><li>Nordstroem, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+and+validation+of+BV14,+a+new+twin+track+fixed+slip+friction+tested+for+winter+road+maintenance+monitoring+in+Sweden.">Development and validation of BV14, a new twin track fixed slip friction tested for winter road maintenance monitoring in Sweden.</a> Proceedings of XTH PIARC International Winter Road Congress. Swedish National Road and Transport Research Institute (VTI). , (1998).</li><li>Norem, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selection+of+strategies+for+winter+maintenance+of+roads+based+on+climatic+parameters.">Selection of strategies for winter maintenance of roads based on climatic parameters.</a> Journal of Cold Regions Engineering. 23 (4), 113-135 (2009).</li><li>Bergstr&#246;m, A., &#197;str&#246;m, H., Magnusson, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Friction+measurement+on+cycleways+using+a+portable+friction+tester.">Friction measurement on cycleways using a portable friction tester.</a> Journal of Cold Regions Engineering. 17 (1), 37-57 (2003).</li><li>Henry, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+pavement+friction+characteristics.">Evaluation of pavement friction characteristics.</a> Transportation Research Board. , (2000).</li><li>ASTM International. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ASTM+E303-93.+Standard+Test+Method+for+Measuring+Surface+Frictional+Properties+Using+the+British+Pendulum+Tester.">ASTM E303-93. Standard Test Method for Measuring Surface Frictional Properties Using the British Pendulum Tester.</a> ASTM International. , (2018).</li><li>ASTM International. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ASTM+D6926-20.+Standard+Practice+for+Preparation+of+Asphalt+Mixture+Specimens+Using+Marshall+Apparatus.">ASTM D6926-20. Standard Practice for Preparation of Asphalt Mixture Specimens Using Marshall Apparatus.</a> ASTM International. , (2020).</li><li>Oliver, J. W., Tredrea, P., Pratt, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Seasonal+variation+of+skid+resistance+in+Australia.+Special+Report+No+37.">Seasonal variation of skid resistance in Australia. Special Report No 37.</a> Australian Road Research Board. , (1988).</li><li>Steven, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Friction+Testing+of+Pavement+Preservation+Treatments:+Temperature+Corrections+and+Operator/Machine+Variability.">Friction Testing of Pavement Preservation Treatments: Temperature Corrections and Operator/Machine Variability.</a> University of California Pavement Research Center Davis and Berkely. , (2009).</li><li>Transport Research Laboratory. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=BS+7976-2:2002.+Pendulum+testers+-+Method+of+operation.">BS 7976-2:2002. Pendulum testers - Method of operation.</a> Transport Research Laboratory. , (2002).</li><li>Lu, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Friction+testing+of+pavement+preservation+treatments:+Literature+review.">Friction testing of pavement preservation treatments: Literature review.</a> UC Davis: University of California Pavement Research Center. , (2006).</li><li>Bazlamit, S. M., Reza, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Changes+in+asphalt+pavement+friction+components+and+adjustment+of+skid+number+for+temperature.">Changes in asphalt pavement friction components and adjustment of skid number for temperature.</a> Journal of Transportation Engineering. 131 (6), 470-476 (2005).</li></ol>

The authors have nothing to disclose.

The present paper examines the procedure for testing the friction coefficient of icy pavement using a BPT. Several points need to be comprehensively analyzed and are discussed in detail here. First, in terms of the preparation of the asphalt mixture samples, one should try to use road petroleum asphalt to prepare the samples, but this is not a requirement. The preparation of the asphalt mixture samples should be performed in strict accordance with the ASTM (D6926-20) experimental protocols, as this affects the accuracy o...

Pavement friction is defined as the grip between the vehicle tires and the underlying road surface1. The index most commonly associated with pavement friction in road design is the pavement friction coefficient. Friction is one of the most important factors in road design and is second only to durability. There is a strong and clear correlation between pavement friction performance and accident risk2. For example, there is a significant negative correlation between road accident rates and pavement skid resistance3,4,5. Several factors may contribute to a decrease in pavement friction, and one of the most direct and influential of these factors is snowfall6. Specifically, snowfall causes ice to form on the pavement, thereby resulting in a significant reduction in the road friction coefficient7,8. A study focusing on the factors that influence traffic accident rates in southern Finland noted that accident rates commonly peak on days with heavy snowfall and that more than 10 cm of snow can lead to a doubling of the accident rate9. Similar results have been found in studies performed both in Sweden and Canada10,11. Therefore, studying the friction properties of snow-frozen pavements is crucial for improving road safety.
Determining the friction coefficient of icy pavements is a complex process because the friction coefficient may vary under different snowfall levels and pavement ice thicknesses. Furthermore, varying temperatures and tire characteristics may also affect the friction coefficient. In the past, numerous experiments have been conducted to study the friction characteristics of tires on ice12. However, due to the differences in individual environments and tire characteristics, consistent results cannot be obtained and used as a basis for theoretical studies. Therefore, many researchers have attempted to develop theoretical models to analyze the friction of tires on ice. Hayhoe and Sahpley13 suggested the concept of wet friction heat exchange at the interface between tires and ice, while Peng et al.14 proposed an advanced data model to predict friction based on the above concept. In addition, Klapproth presented an innovative mathematical model for describing the friction of rough rubber on smooth ice15. However, the above models have been shown to have significant errors, mainly due to their inability to accurately and efficiently characterize the friction properties of tires on ice16.
To reduce the errors of theoretical models, a large amount of experimental data is needed. The Finnish Meteorological Agency developed a friction model for predicting icy pavement friction, and the formula for that model was primarily based on data obtained from road weather stations and through statistical analysis17. Furthermore, Ivanovi&#263; et al. gathered a significant amount of experimental data by analyzing the friction characteristics of tires on ice and calculated the friction coefficient of ice by regression analysis18. Gao et al. also proposed a novel prediction model of tire-rubber-ice traction by combining the Levenberg-Marquardt (LM) optimization algorithm with a neural network to obtain the formula for the friction coefficient on ice19. All the above models have been either validated or applied in practice and are, thus, considered feasible.
In addition to theoretical methods, many practical methods have been developed for measuring the friction coefficient of pavements in snowy and frozen areas. Due to the particularities of the weather, these methods have been widely used in Nordic countries such as Sweden, Norway, and Finland20. In Sweden, the following three main types of friction measuring devices are used: the BV11, SFT, and BV14. The BV14, a dual friction tester developed specifically for winter maintenance assessments, is directly connected to the measuring vehicle and measures the dry friction on both wheel paths simultaneously20. In Finland, the friction measuring vehicle (TIE 475) is used for winter road maintenance assessments, while in Norway, the ROAR friction measuring device (without water) is a commonly used piece of equipment2. Most of the winter friction measurements carried out in Sweden, Norway, and Finland have been performed using ordinary passenger cars with ABS and instruments measuring deceleration under braking2,20. The advantage of this method is that it is simple and relatively inexpensive, and the main disadvantage is that the accuracy of the method is very low.
The studies described above provide methods for predicting and detecting friction coefficients on ice. However, a uniform method and a specific value to guide road designers have still not been provided. Moreover, for winter roads, the friction coefficient between the tires and ice may vary with respect to different ice thicknesses, and different disposal measures should also be implemented21. Therefore, this paper aims to determine the friction coefficient of icy roads under different amounts of snowfall.
Internationally, the British portable tester (BPT) and the Swedish Road and Transport Research Institute portable friction tester (VTI PFT) are currently the most commonly used instruments for measuring the friction coefficient22,23. The PFT is a portable friction tester developed by VTI, and it allows the operator to take measurements in an upright position and save the data on the computer22. The PFT can measure most contoured road markings, but the number of instruments currently available is still very small2. The BPT is a pendulum friction coefficient tester that was developed by the British Road Research Laboratory (RRL, now TRL). The instrument is a dynamic pendulum impact-type tester used to measure the energy loss in cases when a rubber slider edge is propelled over a test surface. The results are reported as British Pendulum Numbers (BPNs) to emphasize that they are specific to this tester and not directly equivalent to those from other devices24. The instrument has been shown to be useful for the determination of friction coefficients in the experimental pavement field23. This experiment uses the BPT for the determination of friction coefficients.
The present study describes the experimental procedure for measuring the friction coefficient of icy pavements corresponding to different snowfall amounts indoors. The problems to be noted in the experiments, such as experimental calibration, experimental implementation, and the methods of data analysis, are explained in detail. The present experimental procedures can be summarized by the following five steps: 1) the preparation of the equipment, 2) the calculation and analysis of the snowfall, 3) equipment calibration, 4) friction coefficient determination, and 5) data analysis.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Brush</td>
			<td>Shenzhen Huarui Brush Industry Co., LTD</td>
			<td>L-31</td>
			<td></td>
		</tr>
		<tr>
			<td>Freezing equipment</td>
			<td>Haier Group</td>
			<td>BC/BD-251HD</td>
			<td></td>
		</tr>
		<tr>
			<td>Measuring cylinder</td>
			<td>Zhaoqing High-tech Zone Qianghong Plastic Mould Co., LTD</td>
			<td>lb1</td>
			<td></td>
		</tr>
		<tr>
			<td>Pavement thermometer&#160;</td>
			<td>Fluke Electronic Insrtument Company</td>
			<td>F62MAX</td>
			<td></td>
		</tr>
		<tr>
			<td>Pendulum Friction Cofficient Meter</td>
			<td>Muyang County Highway Instrument Co., LTD</td>
			<td>/</td>
			<td></td>
		</tr>
		<tr>
			<td>Rubber sheet</td>
			<td>Jiangsu Muyang Xinchen Highway Instrument Co., LTD</td>
			<td>785120123500</td>
			<td></td>
		</tr>
		<tr>
			<td>Sliding length ruler&#160;</td>
			<td>Jiangsu Muyang Xinchen Highway Instrument Co., LTD</td>
			<td>785120123500</td>
			<td></td>
		</tr>
		<tr>
			<td>Tripod</td>
			<td>Hangzhou Ruiqi Trading Co., LTD</td>
			<td>TRGC1169</td>
			<td></td>
		</tr>
	</tbody>
</table>

determination of the friction coefficients of icy pavements under different amounts of snowfall

Ice on road surfaces can lead to a significant decrease in the friction coefficient, thus endangering driving safety. However, there are still no studies that provide exact friction coefficient values for pavements covered in ice, which is detrimental to both road design and the selection of winter road maintenance measures. Therefore, this article presents an experimental method to determine the friction coefficient of icy road surfaces in the winter. A British portable tester (BPT), also known as a pendulum friction coefficient meter, was employed for the experiment. The experiment was divided into the following five steps: the preparation of the equipment, the calculation and analysis of the snowfall, equipment calibration, friction coefficient determination, and data analysis. The accuracy of the final experiment is directly affected by the equipment accuracy, which is described in detail. Moreover, this article suggests a method for calculating the ice thickness for corresponding amounts of snowfall. The results illustrate that even patchy ice formed by very light snowfall may lead to a significant decrease in the friction coefficient of the pavement, thus endangering driving safety. Additionally, the friction coefficient is at its peak when the ice thickness reaches 5 mm, meaning protection measures should be taken to avoid the formation of such ice.

Sample 7 in Table 4 is the dry sample control group, while the remaining samples 1-6 correspond to ice thicknesses ranging from very light snow to a large blizzard.
When comparing sample 7 and the other six groups, ice formation was observed to significantly reduce the friction coefficient of the pavement. Furthermore, the pavement friction coefficient decreased with increasing ice thickness, and the ice thickness tended to stabilize at 5 mm, which corresponds to medium snow. ...

Watch this Scientific Journal Video about Determination of the Friction Coefficients of Icy Pavements Under Different Amounts of Snowfall at JoVE.com

Determination of the Friction Coefficients of Icy Pavements Under Different Amounts of Snowfall

Here, we present a method for determining the friction coefficient of pavements with different ice thicknesses indoors. The complete procedure includes the preparation of the equipment, the calculation and analysis of the snowfall, equipment calibration, friction coefficient determination, and data analysis.

Ice on road surfaces can lead to a significant decrease in the friction coefficient, thus endangering driving safety. However, there are still no studies ...

This video is aimed to show the process of determining the coefficient of friction of an icy road surface. Using the pendulum friction coefficient meter. Ice on the road surface can lead to a significant reduction in the coefficient of friction and thus endanger driver safety.We want to establish a complete and scientific experimental procedure indoors to determine the coefficient of friction of icy road surfaces. A pendulum friction tester was used to conduct in the experiment and asphalt slabs and water layers were frozen simultaneously to simulate road icing. Different levels of snowfall was also simulated on asphalt slab with varying ice thickness to make the results more intuitive.Preparation of the equipment. First, the pendulum friction coefficient meter, during the experiment ensure that B P T is within its surface life and that surface is clean and undamaged. Its components are base, leveling spiral, leveling bubble, pointer, pendulum, lifting spiral, fastening spiral, huddle, and dial.Then the asphalt slab, ensure that asphalt mixture sample size use for experiment is 30 centimeters by 30 centimeters by five centimeters. The right figure shows the asphalt slab wrapped with molds. Next the freezing equipment, ensure that this equipment used in the experiment can freely regulate the temperature between subzero 20 centigrade to zero centigrade.Other equipment used in the experiment includes, tripod, measuring cylinder, rubber sheet, pavement thermometer, sliding length ruler and brush. The size of the rubber sheet used in the experiment is 6.35 millimeters by 25.4 millimeters by 76.2 millimeters and should meet the quality requirements given in the following table. During the experiment, ensure that the rubber sheet has no following defects:First, there are oil stains;Second, rubber sheet width edge wear is greater than 3.2 millimeters.Third, rubber sheet length direction wear is greater than 1.6 millimeters. Before using a new rubber sheet, ensure that the rubber sheet is measured 10 times on a dry surface before employed for official testing. Calculation and analysis of snowfall the table gives the snowfall class classification to consider extreme cases takes 24 hours of snowfall at the condition for the study.Moreover, to ensure the ease of experimentation the upper limits of each level of snowfall division as used for the corresponding calculation and analysis. After calculation, different levels of snowfall test at the corresponding water volume of the samples as provided in the table. Experiment does not consider the influence of the extraordinary snow storms and number the very light snow to big blizzard from 1 to 6.Equipment calibration Place the BPT in a suitable position. A suitable position means that the ground is flat and free of potholes, rotate the leveling spiral on the base of the BPT to keep the leveling bubble in the middle position. Loosen the fastening spiral, rotate the lifting spiral to make the pendulum lift and swing freely.Then tighten the fastening spiral. Place the pendulum arm on the right cantilever of the pendulum table keeping the arm in the risen toe position while rotating the pointer to the right side flush with the arm. Press the release button to let the pendulum arm swing freely and then the pendulum crosses the lowest point.To reach the highest point, hold it by hand. The pointer should indicate zero at this time. If the pointer does not show the zero point loosen and tighten the narrowing nut to make it show the zero point.Place the asphalt slab directly under the pendulum while loosening the fastening spiral so that the lowest edge of the rubber sheet touche the surface of the asphalt slab. Prepare the sliding length ruler and bring it close to the rubber sheet. Lift the carrying handle to make the left scale mark of the sliding length ruler flush with the lowest edge of the rubber sheet.Lift the carrying handle and move the pendulum to the right again so that the lowest edge of the rubber sheet only touches the surface of the asphalt slab. Observe further, the sliding length jeweler is flush with the edge of the rubber sheet. If flush, the sliding length meets a requirement of 136 millimeters.Otherwise, continue the following operation. Turn the lifting spiral to adjust the height of the pendulum to make the sliding length meet the requirements. Vital tan is needed.Twist the level spiral on the base. The level in bubble needs to remain centered during an adjustment. Friction coefficient determination.Select seven pieces of asphalt slabs. Clean their surface with a brush and dry naturally at room temperature. Number the asphalt slabs in turn place the asphalt slabs into modes and simultaneously coup and freeze with the water layer.The sevens samples were placed into the freezer at a controlled temperature in a sub zero 10 centigrade for 24 hours. After freezing, turn down the samples in turn, remove the modes and place them on the BPT centers, which have been leveled and zero use the pavement centimeter to measure the surface temperature of the sample and record, perform sliding length calibration. To ensure sliding distance of 126 millimeters press the pendulum arm release switch and when the pad arm crosses the lowest point and swings to the highest one held by hand, read and recorded restore both the pendulum arm and the pointer to the zero and horizon positions respectively.The sliding length should be re calibrated each time a new sample is tested. Repeat the steps for 10 times. Measure seven samples in sequence.Each sample has 10 measurement results and both the minimum and the maximum value difference should be less than three. Data analysis recorded data in the table and the average measurement results to get average values bring the temperature value measured into the equivalent. To obtain the temperature compensated value subtract the compensated BPN value from average BPN value in the table to obtain the final temperature compensated BPN value plot the final BPN values in table four and the bar graph for more intuitive results.Representative results:When comparing sample seven and the other six groups, I think it is observed to significantly reduce the friction coefficient of the pavement. Based on sample one very light snow force is not to have a serious impact on the road friction coefficient. With respect to sample two, three, and four the surface friction coefficient was observed to gradually decrease for sample four, five and six.The average final BPM values are identical. This may indicate that the road friction coefficient of the ice layer tends to stabilize and another measure of a thicker ice layer is not necessary. The bar graph can better reflect the wide ratio of friction coefficient.Sample one represents very light snow that adhere to the pavement surface after icing resulting the reduction in the pavement friction coefficient and its BPM value decreased by approximately 43%compared to the dry sample. Sample two, three and four correspond to light medium and heavy snow respectively. Among them the BPM value of medium snow is only one half that of light snow because the thickness of the iced layer corresponding to little snow is of like two minimum.The micro structure of the sample surface still affects the friction coefficient value and the BPN is larger. The BPNs of the heavy snow, blizzard and large blizzard samples are the same, which may stop an ice thickness reaches 11 minimum. The rubber sheets can no longer deformed the ice layer by compacting it.Conclusion:The friction coefficients of seven asphalt slabs were determined by means of a pendulum friction coefficient tester, and the final results were corrected for temperature. It can be seen that, the effect of pavement icing on the coefficient of friction is indeed significant, with even slightly light snow resulting in patches of ice reducing the pavement of friction coefficient by about 40%The final results can provide a reference for road design and winter pavement maintenance.

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