(a) Except at the direction of authorized personnel, vehicular traffic may not cross the double white lines that designate the vehicular traffic lanes in a tunnel. (b) Except at the direction of authorized personnel, trucks and slow moving vehicles may be driven only in the right lane of a tunnel. (c) The driver of a vehicle may not sound his horn or flash his headlights in a tunnel. (d) While in a tunnel, a person may not use any cutout or other device that allows exhaust gases to escape a motor without passing through a muffler or silencer.
Maryland Legal Code