Braess's paradox

Question

Let's consider the Braess's paradox. I have question how were computed the Nash Equilibrium points with values $80$ and $85$ before an after adding the route with the value $0$ from $C$ to $D$, respectively here on the page $4$. I mean, what and why we are summing to get the values $80$ and $85$ on the page 4 in the figure $8.2$.

Answer 1

The Nash equilibrium for the picture $8.2$ without the route from $C$ to $D$ is when both routs from $A$ to $C$ and $A$ to $D$ are loaded with 2000 cars which results in $2000/100+45=65$ time in average. When we add the $0$ route form $C$ to $D$ this route becomes a dominant strategy: any other route would now take $85$ minutes (and therefore will be in any NE) with load $4000/100+0+4000/100=80$ time in average.