For roads specifically, it's not necessarily suppressed demand. Commute times are a significant element in peoples' calculations about where to live. Increase r

For roads specifically, it's not necessarily suppressed demand. Commute times are a significant element in peoples' calculations about where to live. Increase road capacity and living further away (with cheaper land, bigger houses and so on) becomes more attractive, which adds to traffic on the road. The road capacity attracts the demand through second order effects.