It is desirable that a calculation method for road structures like partially covered or intermittent tunnels, in which the traffic piston action is expected to drive polluted matter along the road axis and affect the concentration, depends on a respiration phenomenon which takes into account the respiration action as a natural ventilation.
Also in case the road is a trenched structure with an open ceiling part and several intermittent tunnel structures from which the air stream influences the downstream, it is necessary that the concentration is investigated with the traffic piston action in mind.
The calculation method is applicable to the following general road structures :
- Trenched structures in which the width of the open part is smaller than the width of the traffic space. For the layout of the open part, a center opening and a lateral opening should be taken into consideration. According to an experiment carried out in Japan, the basic phenomena of the respiration activity of the central opening may be called similar to those for the lateral opening.
- Trenched structures with several covered parts (tunnel structures) of which the exhaust gas distribution should be uniformed by the traffic piston action.
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Typical type of depressed structures in Japan
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