FAQ | Shadowrun 4 a écrit:

How does vehicle Speed and Acceleration work?

Speed represents the reasonable high-end maximum velocity of the vehicle in meters per Combat Turn (m/CT) without suffering real difficulties (p. 168, SR4A). Acceleration determines the vehicle’s movement rate (see Movement Rate. p. 149, SR4A); the first number is the “Walking” rate and the second number is the “Running” rate (p. 168-169, SR4A). Divide the vehicle’s Movement rate by the number of Initiative Passes in that turn to see how far it travels in each pass.

Billy’s character Shadrach the Sasquatch is driving a GMC Bulldog Step-Van, which has Speed 90 and Acceleration 5/10. Moving along at 30 m/CT along I-4, Shadrach suddenly drives into a Yakuza/Mafia gunfight! The combat has 2 Initiative Passes; at its current movement rate (30 m/CT) the van will cover 15 meters every Action Phase.

Driving a vehicle manually requires a Use Complex Object Complex Action (p. 148, SR4A), driving one remotely over the Matrix requires a Control Device Complex Action (p. 229, SR4A), and issuing a command to the vehicle’s Pilot while it drives itself requires an Issue Command Simple Action (p. 229, SR4A).

Each Initiative Pass the driver chooses whether the vehicle is moving in its “Walking” or “Running” rate (or stops altogether). Once a rate of movement has been declared, the vehicle moves at that rate until the driver’s next Action Phase; the vehicle continues to move at the last rate it was in during passes in which the driver does not have an action. The rate can only be changed when the driver acts again (Movement, p.148, SR4A), or if the vehicle crashes (Crashing, p. 170, SR4A. The driver can attempt to increase the vehicle’s movement rate by making a Vehicle Test (p.168, SR4A); each test adds 5 meters to the vehicle’s movement rate. A vehicle moving at or greater than its Running rate is considered to be running. A vehicle can move up to its Speed rating without trouble; gamemasters should apply modifiers as they feel appropriate for characters that push the vehicle past the Speed rating (p.168, SR4A).

Shadrach started out driving over his “Running” rate, so the GMC Step-Van is officially considered to be “Running” during his first Action Phase, and will cover 15 meters this Action Phase. However, Shadrach doesn’t feel like catching a Yak shuriken and floors the gas pedal. The GM calls for a Reaction + Pilot Ground Vehicle (2) Test, and Billy rolls four hits. Two is enough to continue moving without incident, and the other one Billy uses to improve the GMC Step-Van’s movement rate to 40; the vehicle has progressed 20 meters by the end of the pass.

These rates abstract the process of acceleration a normal vehicle goes through; a vehicle with an Acceleration of 5/10 that is moving at a “Walking” rate will cover 5 meters that Combat Turn – that does not mean that it is moving at 5 m/CT, but that it is accelerating, decelerating, swerving to avoid traffic and objects, and will move 5 meters by the end of the Combat Turn. When the driver decides to move up to a “Running” rate or come to a stop, the driver is causing the vehicle to accelerate or decelerate, accordingly.

Gamemasters should remember that vehicles cannot start or stop on a dime; a GMC Step-van that was moving at 30 m/CT in one Action Phase would be hard pressed to come to a “Walking” rate of 5 m/CT (much less a complete stop!) in the next Action Phase. As a rule of thumb, a vehicle can go from its standard “Running” rate to “Walking” rate, or from it’s “Walking” rate to stationary without difficulty; add 1 to the threshold of the Vehicle Test for every 10 m/CT over these limits if the driver attempts to slow down or stop too quickly. Failure indicates the vehicle has not slowed down sufficiently.

In his second Action Phase, the GMC Step-Van continues to barrel down the road at a “Running” rate of 40 m/CT, and will cover 20 meters this Action Phase. However, Shadrach sees a baby sasquatch crawling across the road twenty meters right in front of him! Instead of swerving, he slams on the brakes, attempting to go from a “Running” movement rate of 30 m/CT to a “Running” rate of 10 m/CT. The GM calls for a Reaction + Pilot Ground Vehicle (3) Test – threshold 1 for the sudden slowdown, and threshold +2 for how fast he’s moving. Billy had better spend a point of Edge if he wants the GMC Step-Van to avoid running over the baby this Action Phase!