3d Logos/Signage

It is illegal. Remove the models with included logos or you could face severe charges.

I think it depends on policy of individual companies. Some defends their IP vigorously and some didn't care at all. I had couple models that featured some red cattle logo on them and those models were removed from cgtrader pretty quickly.

You can't use any logos or brands that are copyrighted, regardless of whether they are modeled into the object, or on an image based texture, or anywhere. Even if it's a blurry detail on the bottom corner of a model - if the outline suggests it's Coca-Cola or Rubbermaid, you can be sued. In the game industry, we always alter logos and brands and make up fictional ones (magazine covers, brands, groups, anything that relates to real world.)

I'm not sure what if you create a blueprint based car model with 95% accuracy and use the logo on it, it seems to work on CG sites, but where I work, it's an absolute no to do such.

Thank you for the responses, I think overall its an interesting topic because on CG im seeing standalone logos of all car manufactuers being sold, but on Turbosquid its not allowed, but you are allowed to sell that manufacturers car with the logo/emblem in it and you can even have it shown on the rims and everything and rendered, which to me equals the same thing, your still using someone elses property, which would then apply to a majority of the models on every single 3d modelling website.