While Google takes a variety of things into consideration to rank a website, website traffic doesn't directly affect a website's ranking. Otherwise, new websites wouldn't have a chance unless they found social media outlets or other ways to receive large amounts traffic when shared.
However, a website's traffic can indirectly affect ranking depending on how long visitors remain on your website. The more direct traffic your website receives, the more it indicates to Google that your website is an authority. If people are consistently visiting, saving, and revisiting your website directly, this tells Google that your website is trustworthy and doesn't deter visitors from staying on your pages.
While large volumes of traffic may not actually influence your ranking at all, visitors who find your website informational or appealing enough to stay can help boost the website.
Google have plainly denied that they use Google Analytics data to determine a website's worth and rank, but webmasters should consider the possibility that they do. Many believe that GA may play a part in algorithm updates, and Google won't be able to track traffic without AdSense, Analytics, or other tracking codes that monitor a number of factors including:
Each of these aspects can be an important channel for traffic, which means that Google may take them into account when visible.
You should keep in mind that Google does pay attention to bounce rate among the hundreds of factors that determine organic ranking. For instance, if someone visits your website from search results, then goes back to the search results and selects another website, Google will catch this and interpret it as a signifier that your website is of lower quality than your competitors.
Ultimately, if you'd like to improve your rankings, what you want for your website is high-quality content that generates rankings with effective white-hat SEO techniques, which can subsequently increase traffic.