When i played NR2003, it was common etiquite(SP?) to leave a line and
indicate through a message which line you were leaving. Ex. Pass low<<<
or Pass high>>>. You didn't have to slow down, just leave that line open.
Also, slightly of topic, you were supposed to indicate through a message
when you were pitting/exiting the pits. That would solve a few problems
in longer races or midrace joinings when people are exiting the pits in the
middle of a race.