This piece is a little old but I doubt the information has changed much, nor is it all that surprising. Here is an article from a December 2008 US New and World Report on "Best Careers 2009: Urban Regional Planner" with the subtitle of "A multi-faceted job for a multi-talented person" Here is what they say:
Now, the real work begins. Today, you're reviewing geographic information system maps and other computer-based data to predict how many city services will be needed, from lampposts to libraries to fire hydrants. What mix of parking garages, additional bus service, and other transportation should be required?