This particular gem was mentioned in the Pilot and Ride skill but not really expanded on outside of those brief passages. Essentially, some vehicles have maneuvers that a skilled driver can employ. For example, the light chariot has Charge and Charge and Turn maneuvers. Charge is rated at Trained skill and Charge and Turn at Experienced Pilot skill.
Charge allows the charioteer to double move that action but lowers REL by d6 points. It also changes the damage you inflict for overruning a foe from 30 + 1/4 movement to 30 + 1/2 movement. Each person run over, however, lowers your speed by half their BODY, just like normal. The maneuver requires a Pilot TD 75 to succeed.
Charge and Turn allows the charioteer double move that action and also make up to a 180-degree direction change at any point. The maneuver requires a TD 50 + angle of the change. You can make more than one direction change but the total must not exceed 180 degrees and each requires its own skill check.
For example, a 220 ft movement with four, 45-degree changes would require four TD 95 Pilot skill checks.
Chariots are not the only vehicles, of course, with maneuvers. Most do have at least one and many two, three or more.