(apologies if this is an old question)

What exactly does this rating cover? It can't be Deleted Scenes or Alternate Endings because we already have ratings for them.

Are film set vehicles (like lorries and motorhomes) that appear in making of documentaries like trucks and motorhomes worth listing? I don't think they are. Neither are limos from film premieres.

I would venture to say it applies to almost anything (except planes, lawn mowers, etc) that is well visible, rare, etc.

I personally would not list set vehicles or background vehicles seen in extra DVD contents, unless they were blatantly visible, so in which case, it might be better to list them case-by-case. If not, just give them a honorable mention on the movie comments page.

This rating was rather made for small extras(typically mini stories / short movies) that can be found on some DVDs.
e.g. http://www.imcdb.org/vehicle_5108-Dodge-Stealth-1991.html

Or some seen in the making-off and which have some interest to be listed.

The Limo example can be used for very special ones, e.g. http://www.imcdb.org/vehicle_230213-Renault-16-Stretched-Limousine.html
but indeed for common limos/motorhomes seen in extras it is not worth listing.

Of course some people will use (or have used) this rating to add pointless stuff (ordinary lorries etc).

Here's one movie with lots of "Seen only in an extra DVD contents" http://www.imcdb.org/movie_240636-Johnny-Hallyday-au-Parc-des-Princes.html

If only there was a search by rating function* so we could see all the things with this rating (or maybe you [antp] are able to find all of them using code or something?)

*Although I'm not saying put this at the top of the list of new features to add

Sometimes a car can only be part seen in the actual movie, not enough for its own listing yet it's visible throughout the scene, but some behind the scenes video shows it more clearly.

Too, there's the case of "Route 66," whose extras include Chevrolet commercials that ran when the show first aired on the network. That's significant because some of those vehicles were rare, like the Corvair Rampside pickup.

Until then you can sort by rating, and find the special ratings at the end

How do you do that?

Select Importance/Role in the Display Options Field?

Like here: http://www.imcdb.org/movie.php?resultsStyle=asImages&sortBy=4&id=103776

Yes, and if you do a vehicle search by leaving make & model field, you get the list of all the vehicles of the site, which you can also sort by rating.

I have a question, I have seen short subject for internet viewer only that contains short stories that is related to the History Channel's IRT: Deadliest Road. I could capture these extras and post them at the main IRT: Deadliest Road page with "DVD extra scene" that I could put it in, but these short subject have titles in it. Should I post the name of the short subject after this has been validated? Please advise.

I am not sure that it is really worth listing... what kind of vehicle contains do these have?

I haven't decided yet. There was a scene with full of Indian traffic jams that could been worth posting if I see one

That's the answer I was looking for, thanks