[Impala]

It's easy peasy ... Switch off the ignition, then push the wiper stalk down briefly and release as if you were doing a flick wipe - the wiper arms will stop at the top of the flick wipe stroke. You have to do this within a few seconds after switching the ignition off. To return the arms to the normal park position, switch on the ignition and do another flick wipe.

Additional tips;

• To avoid 'wiping' on a dry windscreen, I suggest doing a brief wash/wipe before moving the arms to the service position as described above.
  
  
• If the windscreen and/or blades have dried while in the service position, I suggest doing a wash/wipe to return the arms to the normal park position instead of just the 'flick wipe' described above.
  
  
• When there is a risk of freezing rain, sleet or snow, then leaving the arms in the service position overnight helps to prevent the blades freezing on to the glass as any 'water' will be able to drain away.
  
  
• When I use a plastic sheet to cover the windscreen to protect against frost or snow, I move the arms to the service position and lift the blades clear of the glass before fitting the plastic sheet, then I put the blades back down on top of the plastic sheet and leave them in the service position and finish by opening each of the front doors in turn, tuck the plastic sheet in to the inside of the car and close the door(s). Removal of the plastic sheet is a reversal of the above, but I suggest returning the arms to the park position while the blades are folded off the glass rather than doing a dry wipe or using the wash/wipe which would freeze on the cold glass. In my experience, the arms on the T-Roc do not touch the bonnet when doing this, unlike my previous Golf where the hinge in the arms was in a different position.