QUOTE (Draco18s @ Aug 18 2011, 03:56 AM)

"You chase your opponent at high speed around a hard right turn."
What do the rules say for resolving this?
Assume that this is an ongoing chase and initiate has already been rolled.
By RAW:
Precise maneuvering is not a factor in chase combat. The only maneuvers available to chase combat are Break Off, Cut Off, Maneuver (to get a dice bonus on next turn's initial opposed roll, fully abstract) and Ram. And yes -unless anything has been published since to add to this- this list is exhaustive, as indicated by
QUOTE (SR4A pg 170)
Drivers must spend one Complex Action each Chase Turn controlling their vehicle. If they choose, they may spend this Complex Action performing
one of the following Chase Stunts.
If initiative had already been rolled, the case you present would likely be a narrative resolution of the Maneuver stunt, the 'high speed' being indicative of "hey, you get some extra dice on your roll next turn." This would have required a success test. Setting the Threshold for which depends on your reading of the rules.
I would probably handwave the specific action taken as irrelevant 9to the crunch) narrative detail, due to the abstract nature of chase combat. This would make the Threshold equal to (appropriate terrain modifiers). Dice pool modifiers to the Vehicle test apply as normal. Alternatively, you might wish to call for specific actions, which would make the Threshold (Action + terrain modifiers) or in this case, (2 + terrain modifiers). I allow this route, but allow for bonusses when people handicap themselves thus.
Note that conditions of traffic, street width, etc only have a bearing on chase combat for the Break Off and Maneuver stunts, which both require a success test. The other two require only an opposed test.
The precise maneuvering stuff is the domain of tactical combat, which does away with the abstract nature of chase combat, and the opposed vehicle roll to start 60-seconds turns off, to replace them with specific and precise maneuvering in normal 3-second turns. In tactical combat, this would definitely be a success test with a Threshold of (2 + terrain modifiers).