While most articles in ScienceDirect are freely accessible to VDOT employees who have created an account, most of those articles are not technically "free" but are covered by VDOT's licensing fees.
Non-subscribers (people outside of VDOT) who find those same articles will see everything VDOT users see, right up until the time they are prompted to purchase most articles (at retail cost) using a credit card. The exception in ScienceDirect is for articles that have been published through "Open Access."
We created a complete guide called Understanding Open Access to explain Open Access fully, but the thing to know is that Open Access articles are freely available for anyone to read, download and reuse in accordance with the user license displayed on each article.
So when you search ScienceDirect, if you get a list of results back and one of them has the markings shown below (a green dot and the wording "Open access" as well as the "Download PDF" link) it is an "Open Access" article and therefore you can get the full text with one click. It won't matter what kind of account you have or even if you have an account:
If you happen to click on Article preview you'll see the full record for the article, which is even more explicitly marked with the pdf icon the words "Download PDF" and also links to the Creative Commons license and access rights for the article, shown in red below:
This Open Access Page on ScienceDirect allows you to search through thousands of articles in ScienceDirect that are freely accessible because they are Open Access.