Maryland Statutes
Subtitle 14 - Operation of Vehicles on Certain Toll Facilities
Section 21-1412 - Special Provisions for Tunnels

(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.