a
a
d
d
b
b
c
e
a = vehicle width
b = lane width
c = traveled-way width
d = hard-shoulder width
e = grading width
Width for
Width for
Flow Possibilities
Wheeled Vehicles
Tracked Vehicles
Isolated vehicles of appropriate width
At least 3.5 m (11.5 ft)
At least 4 m (13 ft)
only and in one direction only
Generally one way only; no overtaking
>3.5 to 5.5 m (11.5 to 18 ft)
>4 to 6 m (13 to 19.5 ft)
or passing in the opposite direction
Single flow
>5.5 to 7.3 m (18 to 24 ft)
>6 to 8 m (19.5 to 26 ft)
Double flow
>7.3 m (24 ft)
>8 m (26 ft)
Figure 2-2. Route Widths
b.
Route Type. For classification purposes, routes are designated by their ability
to withstand the effects of the weather. The worst section of the route determines the route
type. The three route types are as follows:
Type X. This is an all-weather route that with reasonable
maintenance is passable throughout the year to maximum-capacity
traffic. The roads that form this route type normally have waterproof
surfaces and are only slightly affected by precipitation or precipitation
with temperature changes. At no time is this route closed to traffic by
weather conditions other than temporary snow or flood blockage.
2-3
EN 5621
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