Work on this report began in September 2001 as a continuation of the work carried out on unidirectional tunnels. This report covers tunnels with a single gallery and two directions of travel. Examination of appropriate national standards and recommendations, as well as various PIARC ducuments and those of other international organisations in response to recent accidents took place prior to drafting the report. The conclusions and recommendations of the report are based on common practice in various countries, as well as the opinions of PIARC Committee experts. A summary of the main recommendations and international standards governing bi-directional tunnels is given for France, Norway, Spain and the UK. Topics discussed in the report include traffic speed and densities, breakdown and accident rates, horizontal alignment, vertical alignment, geometric cross-section, special elements and maintenance operations.
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