Consequences of a trench run for you: A vehicle engaged in a trench run must select the trench run action on every turn, and it cannot move out of the target ship's square until it disengages (see below). While engaged in a trench run, you cannot attack any target other than the target ship or another ship currently involved in the same trench run. If the target ship moves, you move with it.

Consequences of a trench run for the target vehicle: You can fire at any target not currently engaged in a trench run against you as normal. To attack a ship engaged in a trench run against you, you must make an opposed Pilot check as a standard action. If you win the opposed check, you may make a single attack with a vehicle weapon as a swift action. If you fail, you cannot attack the target.

Firing into a trench run: A vehicle firing at a target engaged in a trench run takes a -5 penalty on its attack roll unless the gunner has the Precise Shot feat.

Disengaging from a trench run: Make an opposed Pilot check as a move action. If you win the opposed check, you successfully disengage from the trench run and may move a number of squares equal to your speed. If you fail, you remain in the trench run, and any gunners on your vehicle take a -5 penalty on any attack rolls they make until your next turn.

Attack of Opportunity: If an enemy ship of at least two size categories larger than you tries to move through your square or an adjacent square, you may attempt to initiate a trench run as an attack of opportunity.