Something must be done to ease traffic congestion. In traditional

Traffic congestion = traffic jam.

Pretend you're driving in a traffic jam. You wish you could go faster, because it's taking FOREVER to get where you're going.

A-->Would it solve the problem if suddenly all the street signs said 70mph instead of 55mph?

Of course not, because you're stuck in traffic! You can only go as fast as the car in front of you.

D-->Would it solve the problem if a cop pulled you over and gave you a ticket for going under 55mph?

Of course not. You say to the cop, "How am I supposed to go 55mph in the midst of a traffic jam? The car in front of me is only creeping forward at 10mph!"

The only thing that's going to fix the problem and let you go faster is if we have more lanes or fewer cars on the road.

(E) is a step towards getting fewer cars on the road. And it reinforces the info we got about what contributed to creating this traffic problem: people used to work and shop locally and now they have to drive farther distances to get to those same destinations.

(B) this would just move the traffic congestion problem from highways to secondary roads.

(C) having MORE people in the suburbs would only ADD cars into the local traffic mix, thereby worsening the problem