If you're unable to attend your event for any reason, you can request the name on your voucher be changed and transferred to someone else, so they can make use of the voucher.
This can only be authorised by the person who originally purchased the voucher. If you're booked on to date for your event, there may be a small fee to change the name on your booking, although this would depend on which events team is running your driving experience or track day.