Try driving in rush hour traffic in the SF Bay Area, then imagine what it&#x27;ll be like in a few decades when there are 40% more people in the area.<p>You can replace gasoline powered cars with electrics, but you can&#x27;t build enough roads to handle the traffic -- there&#x27;s going to have to be improvements in public transportation <i>and</i> smart planning to let people live closer to where they work and play.<p>Retrofitting cities with pub transit is expensive today, but it will be even more expensive tomorrow.