When on an unmotorized vehicle like a wheelchair or skateboard you would be able to engage a 'skitch' verb that functions like grapple (and could even be grapple). You would be chained to the vehicle and adopt its speed as it traverses until you 'unskitch' (or maybe even release).
During this endeavor, you would face the appropriate strength and vehicle operation checks to remain on the vehicle and attached to car. Failure with strength would mean you let go and face a potential accidents pending a higher vehicle operation check. Failure with vehicle operation would mean you lose your unmotorized vehicle but remain holding the vehicle in question, being dragged along and taking damage until you 'unskitch', failed a strength check or lose consciousness.
In addition, those stealth-inclined would engage in an automatic challenge with people in the vehicle. If passed, they would not notice the person hanging on to the vehicle.