If you’re desperate for a smile while stuck in Seattle-area traffic, just look toward the billboards where Washington state has launched a $4.4 million marketing campaign that promotes the new Highway 99 tunnel as resembling a happy face. The messages remind motorists this four-lane tunnel goes completely under downtown, from the stadiums to the Space Needle. Television ads depict people performing a swooping “under” gesture — for instance, while ordering a chicken sandwich with meat beneath the lettuce. Viewers are encouraged to check www.99tunnel.com. The shape resembles the trademark smile of Amazon, which dominates several blocks near the tunnel’s north...