No road work really “eases” traffic. It spreads it out, although it also brings back more people who are working weird hours or taking longer routes.
There is a level of pain we get used to, and if you make the roads wider, more people WILL use them, and that tends to keep the pain levels the same, but it will still help because MORE people will be able to live a more normal schedule or drive less distance.
“Easing traffic” is a poor metric for heavily congested roads, the real measure is how many people are willing to USE the roads, and if you make them wider, more people will be willing to drive them.