People are willing to pay a certain amount of time to drive on a road. This is your demand curve. Everyone willing to spend any amount of time driving makes up all of your demand.
Your supply curve is the speed the road can provide. Increase the average speed by removing stop lights, decreasing congestion, etc and you capture more of the demand.
The only way a road increases demand is if people move to a location they refused to consider before the existence of the road. However, non of the analysis on induced demand for roads analyzes this (that I’ve seen on the academic side). All of it is mistaking capturing more of the demand curve for increasing demand because the effect is always immediate.