ARM 38.4.406
ARM 38.4.406. OVERHEAD CLEARANCE IN TUNNELS AND BRIDGES
Cite as Mont. Admin. R. 38.4.406
(1) Minimum overhead clearance in tunnels and through bridges may be decreased to the extent defined by the half-circumference of a circle having a radius of eight (8) feet and tangent to a horizontal line twenty-two (22) feet six (6) inches over top of rail at a point directly over the centerline of track.