This study aims to clarify process of outcome index on winter road traffic service based on user concerns. Firstly, we carry out questionnaire survey on user concerns in order to grasp their actual condition of trip and daily activity cause influence to satisfaction of administrative road improvement in snowfall. Secondly, we clarify causal relationship between actual condition of users trip and activity and evaluation to administrative road improvement by Covariance Structure Analysis method. Finally, we clarify process of outcome index methodically reflecting user concerns to winter road traffic service by causal structure model.

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This paper describes water vapor transfer coefficients related to sublimation and evaporation, and heat transfer coefficients between atmosphere and pavement surface under dry, wet, ice plates and packed snow, obtained from wind tunnel tests and a heat energy balance model. In particular, the contact surface area between an asphalt pavement and a snow/ice layer was taken into consideration in the heat conduction flux supplied from the pavement.Consequently, the roughness heights of four kinds of pavement surfaces mentioned above were obtained. Moreover, the heat and water vapor transfer coefficients were formulated as a function of the friction velocity for each surface.

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A temperature controlled pavement has a significant requirement for preventing road from freezing, and for avoiding winter traffic accidents at specific places. For example, a slip accident at tunnel mouth frequently occurs in winter and causes serious danger for human life and a heavy traffic jam. A Horizontal U-Tube (HUT) road heating system was introduced in order to prevent traffic accidents associated with a road freezing at the west side mouth of Nanaori-Toge tunnel, Aizu-bange, Fukushima Prefecture in Japan. A group of Horizontal U-tubes were buried at a depth of 1.2 m in the ground of the central part of the tunnel. The ground heat extracted by the HUT is injected into the anti-freezing pavement blocks made of concrete at the tunnel mouth through a heat injection pipe mounted in each block. Extensive field experiments have been carried out to investigate the pavement surface temperature, extracted ground heat and micro-meteorological characteristics inside and outside the tunnel. This paper presents the field experimental results at Nanaori-Toge tunnel regarding road anti-freezing and ground heat extraction performance of the HUT system. Even when air temperature was 4 °C lower than the freezing point, the anti-freezing pavement connected with the HUT could keep positive. It is concluded that the HUT road heating system using shallow ground heat in the tunnel is effective in preventing the road surface freezing at tunnel mouth.

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