The graphic designer has a misinformed idea about engineering.

Cars are not meant to travel fast through cities.

This is true. City traffic planning was designed to maximize efficiency, not speed. This is no longer the case of many cities which now engineer congestion into design.

Rush hour traffic still goes to a crawl

People assume traffic represents failure, but the road still holds capacity, even if flowing slowly. Government data collection on infrastructure utilization and traffic recovery is prohibited in my area by vocal minorities to obstruct studies countering their goal objectives.

... Something something Trains

Trains are fun!

Just one more lane will fix it

I agree adding one lane won't "fix" traffic. Cities are organic and traffic balances out with infrastructure pressure and necessary.

On the other hand, many lanes around my area have converted to dynamically priced toll lanes; the resulting increase in congestion for remaining lanes drives up the cost of tolls. This has been very profitable for the government and flies in the face of this argument; if it were true, it wouldn't be so lucrative.