Economy and nonproductive sectors of each country could not function without a transport system (TS) Having analysed research works on the interaction of separate TS elements, it was identified that there is no common model for all types of interaction TS consists of material (physical) objects: traffic participants and freight to be carried, a transportation process and operations’ control TS classification scheme devised according to systematically selected criteria, showing that several criteria are often applied at the same time in official documents, is presented Original TS physical elements’ interaction model with 6 interaction levels is presented as well The model is suitable for all modes of transport Six levels of interaction are distinguished: autointeraction of transport elements, the first level; TS elements’ interaction, the second level; TS elements’ interaction with external environment, the third level; interaction of transport modes, the fourth level; TS interaction with t

/pdf/modelling-the-interaction-of-transport-system-elements-rkqe6prbua.pdf

Modelling the interaction of transport system elements

The surface of windy Antarctic snowfields is subject to drifting snow, which leads to the formation of sastrugi. In turn, sastrugi contribute to the drag exerted by the snow surface on the atmosphere and hence influence drifting snow. Although the surface drag over rough sastrugi fields has been estimated for individual locations in Antarctica, its variation over time and with respect to drifting snow has received little attention. Using year-round data from a meteorological mast, seasonal variations in the neutral drag coefficient at a height of 10 m $$(C_{{ DN}10})$$
 in coastal Adelie Land are presented and discussed in light of the formation and behaviour of sastrugi based on observed aeolian erosion patterns. The measurements revealed high $$C_{{ DN}10} $$
 values $$(\ge $$
  2 
 $$\times $$
 10
 $$^{-3})$$
 and limited drifting snow (35% of the time) in summer (December–February) versus lower $$C_{{ DN}10} $$
 values $$(\approx $$
  1.5 
 $$\times $$
 $$10^{-3})$$
 associated with more frequent drifting snow (70% of the time) in winter (March–November). Without the seasonal distinction, there was no clear dependence of $$C_{{ DN}10} $$
 on friction velocity or wind direction, but observations revealed a general increase in $$C_{{ DN}10} $$
 with rising air temperature. The main hypothesis defended here is that higher temperatures increase snow cohesion and the development of sastrugi just after snow deposition while inhibiting the sastrugi streamlining process by raising the erosion threshold. This increases the contribution of the sastrugi form drag to the total surface drag in summer when winds are lighter and more variable. The analysis also showed that, in the absence of erosion, single snowfall events can reduce $$C_{{ DN}10} $$
 to $$1\,\times \,10^{-3}$$
 due to the burying of pre-existing microrelief under newly deposited snow. The results suggest that polar atmospheric models should account for spatial and temporal variations in snow surface roughness through a dynamic representation of the sastrugi form drag.

Seasonal Variations in Drag Coefficient over a Sastrugi-Covered Snowfield in Coastal East Antarctica

. A long-standing problem in avalanche engineering is to design defense structures and manage forest stands such that they can withstand the forces of the natural snow cover. In this way, glide-snow avalanches can be prevented. Ground friction plays a crucial role in this process. To verify existing guidelines, we collected data on the vegetation cover and terrain characteristics of 101 glide-snow release areas in Davos, Switzerland. We quantified the Coulomb friction parameter μm by applying a physical model that accounts for the dynamic forces of the moving snow in the stauch zone. We investigated the role of glide length, slope steepness and friction in avalanche release. Our calculations revealed that the slope angle and slab length for smooth slopes correspond to the technical guidelines for defense structure distances in Switzerland. Artificial defense structures, built in accordance with guidelines, prevent glide-snow avalanche releases, even when the terrain is smooth. Slopes over 40 m in length and 45° in steepness require a ground friction of μm = 0.7 corresponding to stumps or tree regeneration to ensure protection. Forest management guidelines that define maximum forest gap sizes to prevent glide-snow avalanche release neglect the role of surface roughness and therefore underestimate the danger on smooth slopes.

Quantification of basal friction for technical and silvicultural glide-snow avalanche mitigation measures

Socio-economic effects of studded tire use in alaska

Natural sintering in ice is a fundamental process determining mechanical properties of various ice forms. According to the literature, limited data are available about the complex subjects of snow sintering and bond formation. Here, through cold laboratory mechanical tests with a new shear apparatus we demonstrate time-dependent effects of isothermal sintering on interface strengthening at various normal pressures. Measurements showed that interfacial strength evolved rapidly, conforming to a power law (mean exponent a 0.21); higher pressure corresponded to higher initial strength and sintering rates. Our findings are consistent with observations on homogeneous snow, provide unique records essential for slope stability models and indicate the significant importance of normal load on data interpretation.

/pdf/healing-of-snow-surface-to-surface-contacts-by-isothermal-2kvn8aghn3.pdf

Healing of snow surface-to-surface contacts by isothermal sintering

吹雪による視程障害の発生状況に関する情報は,ドライバーが安全かつ適切な経路選択を行う上で有効である.道路における視程障害の監視には,視程計が用いられているが,設置個所は一部の箇所に限られており,広域的な吹雪の発生状況を把握するには不十分である.そこで,比較的容易に得られる風速や降雪強度から,視程障害の程度を推定する手法を検討した.最初に,飛雪流量(Mf)と視程(Vis)に関する竹内・福沢(1976)の研究より,視程が3000 m以下のデータから両者にはlog(Vi)=-0.773・log(Mf)+2.845なる関係式が成り立つことを示した.飛雪流量は飛雪濃度と風速の積であることから,次に,飛雪濃度を求める方法を検討した.ここでは,高さ10mでの風速が8.5m/s以上でかつ気温が-2℃未満の条件と,高さ10mでの風速が8.5m/s未満または気温が-2℃以上の降雪時という条件に分けて,風速と降雪強度から飛雪濃度を推定する方法を示した.これらの式を用いた視程の推定結果と実測例とを比較したところ,1000 m以下の視程において,両者は比較的良く一致した.このことは,この視程推定手法が,道路における視程障害の広域監視に十分有効であることを示すものである.

A study of methods to estimate visibility based on weather conditions

Abstract An experiment using artificial snow was conducted to clarify the influences of temperature and normal load on temporal variations in the shear strength of snow. Artificial snow consisting of dendritic crystals was allowed to accumulate to ∼60 cm depth for the experiment. The shear strength, temperature and weight of the overlying snow were measured at three different depths in the accumulated snow. For the measurement of shear strength, the shear frame index (SFI) was found using a shear frame by placing weights with different masses on the snow contained within the frame. The measured SFI values were treated with the Mohr–Coulomb failure criterion to find the snow cohesion factor C and the internal friction factor tanϕ. The results highlighted similar trends for SFI and C values by which their rate of increase over time was greater with higher snow temperatures and normal load caused by overlying snow. This indicates that C contributes significantly to increased SFI values. tanϕ decreased over time with higher snow temperatures and increased with lower snow temperatures. In low-temperature conditions, in particular, it is likely that snow crystals are compacted but maintain their dendritic morphology.

The influences of temperature and normal load on the shear strength of snow consisting of precipitation particles

Road meteorological observatories measure visibility with visibility meters. However, visibility values measured by visibility meters stem from the meteorological definition, which comes from a perspective different from that of road use. Subject experiments were therefore conducted with road videos in blowing snow conditions to clarify the difference between visibility perceived by drivers and that measured with a visibility meter. The experiments revealed that visibility perceived by drivers in blowing snow was approximately 70 m lower than conventionally measured visibility. Also, a high correlation was observed between the visibility perceived by drivers and the sum total of projected area of snow particles passed through a unit area in a unit time. It was also learned that the visibility perceived by drivers during blowing snow was affected by the intensity of visibility fluctuation, the presence or absence of snowfall, road surface conditions, the surrounding environment (i.e., urban or suburban), and the time of day, and is hardly influenced at all by the direction of the snowstorm. On the basis of the above results, the need for a visibility index for road traffic in blowing snow was suggested.

How Drivers Perceive Visibility in Blowing Snow: Human Subject Experiments on Visibility—Viewing Videos of Blowing Snow

https://www.jstage.jst.go.jp/article/seppyo1941/53/4/53_4_309/_pdf

Masaru Matsuzawa

Papers

A study of methods to estimate visibility based on weather conditions

The influences of temperature and normal load on the shear strength of snow consisting of precipitation particles

How Drivers Perceive Visibility in Blowing Snow: Human Subject Experiments on Visibility—Viewing Videos of Blowing Snow

Motions and vertical profiles of blowing snow particles

Improving visibility estimation under snowstorm