While most of the focus of your model railroad layout is on trains, other vehicles play a big part in bringing the layout to life. Compared to locomotives, train cars, and buildings, vehicles have the shortest usage lifespan. This means that you can get away with using the prior three to model multiple time periods as their life expectancies tend to last anywhere from 40-100+ years depending on which one you're talking about. Most vehicles, on the other hand, aren't used for as long, so they act as a better indicator of the era. That's why it is important to use vehicles on your layout to match up with the time period from which you are modeling.
There are some fine examples of n scale vehicles available in the marketplace today. However, up until recently, it has been a challenge to find n scale vehicles from the 1970's up through today. With the advent of online 3D printing marketplaces such as Shapeways, there has been an explosion of new options from this time period.
Over the years, I have put together a list of vendors that produce modern era n scale vehicles for my own personal layouts. I felt that it was high time to share this list. Some of them make their own, some of them sell other manufacturer's products. Some are produced using a resin cast, while others have converted to 3D printing. There's a little bit of everything!