16 for me.
Having waited 7 years to get a diagnoses for my son, I would urge you not to place too much by your scores.
All the questions are just looking for traits which MIGHT be Autism related, but many of which are shared by a whole range of other conditions.
There are many many other symptoms which go to make up a diagnoses - few of which are exclusive to the condition.
The American Autism Society have a diagnostic description on their website which is better than the questionnaire you have been looking at, but because the shared symptoms, and differing perceptions of YOUR OWN behaviour can mislead, I shall refrain from putting it up here!
If anyone wants a good book which describes the condition from somebody who has experienced it, try ""Freaks, Geeks and Asperger Syndrome" by Luke Jackson. Luke was just 13 when he wrote down what he was experiencing!
A good multimedia resource is "A for Autism" from Channel 4 - an 11 minute documentary description - again by those who have experienced it, or BBC TV's "The Autism Puzzle", an hour long documentary describing the background to the condition, AND contemporary thinking on it's causes and manifestations.
Those with autism can suffer sensory overload, because their brain is unable to sort and filter the massive amount of information ALL their senses take in. With my son, this leads to him blocking out sounds by placing his hands over his ears, to reduce the input.
With others, they might try to block their sense of touch by clutching their arms around themselves tightly. This might look silly to the casual observer, but is merely a "safety" or comfort mechanism for that individual.
While at times it can be frustrating having to recognise, and learn to deal with their little foibles, on the whole, living with somebody with autistic spectrum conditions gives YOU an increased awareness of many things you would normally take for granted, so I can honestly say that it has been a real pleasure living with our son's condition, it has taught me a great deal, and I would not wish it to simply go away for my own sake.
As with ANY condition which might affect driving, it is important that the driver is aware of anything which might affect his/her judgement, or reactions. Presumably this SHOULD come out in the test, yet I see people trying to park outside my works, while under no pressure at all, and making a complete a**e of it, and I wonder how they got their licenses!