According to Porsche the 919 race car Steering wheel it’s a multi-function rectangle and the shape is due to the space required during quick driver changes. A round steering wheel wouldn’t allow enough room for the legs of taller drivers like Mark Webber or Brendon Hartley to fit in easily.
The blue button at the top right which is almost always in use, is the headlamp flasher, used by the fast prototypes to warn the slower vehicles in the WEC field before they are lapped. When pushed once, it causes the headlamps to flash three times. In daylight, the drivers keep their thumb on it almost permanently, as naturally the headlamp signal is more difficult to perceive at that time.
The red button at the top left is also highly frequented. It is used to demand electrical power from the battery, the so-called “boost”. The drivers can boost to pass but must be clever about rationing the power. The amount of energy per lap is specified. The yardstick is one lap in Le Mans, where six megajoules are available. The amounts are converted accordingly for shorter circuits. The amount of energy a driver uses in the middle of a lap to get free of the traffic will not be available at the end in the straightaways.
A bit further inside on the right and left are the plus and minus switches to adjust the front and rear traction control and to distribute the brake balance between the front and rear axle. These (yellow, blue and pink) are not used quite as frequently.
The orange buttons further down operate the drinking system (on left) and put the transmission in neutral (on right). The red button at the bottom left is for the windscreen washer, the red one on the right side activates the cruise control to restrict the speed in the pit lane.
At the top centre, there are the green buttons for radio communication (on the left) as well as the OK button on the right. Drivers use the latter to confirm they have performed a setting change, which was requested from them via the pit radio. For these settings, they use the rotary switches, and usually only in the straightaways as they need to pull one hand out of the steering wheel grip for this purpose.
The two rotary switches called ‘Multi’ correspond with one another. The left one is available for ABC settings, the right one is number-based. Programmes for engine management or fuel management are designated by combinations such as A2 or B3. Three other rotary switches are available to pre-select the brake balance, set the traction control for wet or dry conditions and the hybrid strategy.