threshold zone, <of a road tunnel>

first part of a road tunnel, directly after the entrance portal

Note 1 to entry: The threshold zone starts either at the beginning of the road tunnel or at the beginning of the sun screen when a sun screen is installed. The length of the threshold zone is at least equal to the stopping distance.

Note 2 to entry: This entry was numbered 17-1314 in CIE S 017:2011.

Publication date: 2020-12
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