Former transportation engineering prof here. This is exactly right. And for many transportation engineers, it's a reason to support toll lanes and to oppose adding (other) lanes. But I agree with some of the other commenters here, that adding lanes supports greater movement of people and goods and, separately, that toll lanes are regressive and come with plenty of (other) issues that are often ignored. My personal take on this is that toll lanes and congestion charging are the most effective methods we know for relieving congestion BUT that they are an incredibly difficult sell politically and maybe for good reason; maybe their issue are worse than the congestion they mitigate.