"Consider this paradox: if everyone is flying, by definition there is no surface traffic, ergo no surface gridlock, so then why is anyone flying?"<p>False dichotomy based on juggling with the meanings of "everyone". Observe a real world example: there is virtually no passenger travel by ship, everyone is flying; so why was the Panama Canal upgraded a few days ago? <i>Cargo.</i> Surface shipping is cheap if the payload doesn't complain - be it on sea or on tarmac.<p>Also, governments tend to spend money on road infrastructure for <i>other reasons</i> than passenger traffic. Observe this traffic sign for one: <a href="http://c8.alamy.com/comp/BD1JNH/military-weight-loading-road-sign-for-vehicle-types-in-germany-europe-BD1JNH.jpg" rel="nofollow">http://c8.alamy.com/comp/BD1JNH/military-weight-loading-road...</a>