I can only remember seeing two. I was at school at Oxford in the '50s, and saw the Wolseley 1500's forebear when it was still being tested as a replacement for the Series II Morris Minor, possibly with the Minor 1000's 948cc engine; you can only be grateful nothing came of that! It would have spoiled what turned out to be two very good cars. The other occasion was in the '80s when I saw a production prototype Jaguar XJ40 on the A49 near Ross-on-Wye, several months before it came out. I may have drooled a bit

I've only seen one prototype on the road. It was a disguised Lancia Thesis somewhere near Aachen I seem to remember.

I’ve seen two test-mules in my lifetime. However, I think they were both redesigns rather than being All-New vehicles. I saw one on I-95 heading into Georgia and another one the Blue Ridge parkway in the Smoky Mountains.

Each time I saw one I got really excited, but my kids were like; "Dad why are you so happy? .... its just a car with black stuff all over it"

I got the idea about this by the "car-sights"-thread.

In the past I've seen the following prototypes on the road, outside of car-museums or -shows or in car-plants.

- in autum 1993 I wondered on the Autobahn North of München/Munich about a BMW 3-series, which looks quite short. Later I've found out, that it was a "compact": http://en.wikipedia.org/wiki/BMW_Compact

- in 1992 an unknown Mercedes Benz passed me in the town center of Hannover. It was a C-Klasse W 202.

- in 2000 I was standing with a Japanese friend in front of the "Westfalia"-factory in Rheda-Wiedenbrück. They had a VW T4-Transporter (just the chassis with the drivers house and an obviously selfmade platform). So man details were different to a regular T4, that is was surely a prototype.
A propos T4: the prototypes of it were to see in 1989 in the VW plant in Hannover.

- in 2003 I've visited my Japanese friend at home. On the curved street up to the Mount Fuji there was an unknown car (unkwon for me, my knowledge about actual japanese cars is extremely low) in front of us, which accelerated quite hard, to try obviously to escaping from us.
Later my friend heard from his friend, which is working for Subaru, that it was a prototype indeed. After they saw us, they thought, we were journalists on a prototype-expedition. So we had made an suspicious impression.



But for people, whoe are living close to car-factory, it's nothing special to see prototypes. A friend of mine has worked for 31 years as a developing-engineer in the VW Passat-factory in Emden. He used prototypes as regualr company-cars. He went with them to vacations, too - or to our K 70-club-meetings, when the weather was too bad for driving his K 70.