Problem:  As locating parking spots becomes more difficult in urban areas, drivers are wasting more time than ever looking for a spot to park their car.  This is time wasted that could be used for other productive tasks.  It also results in cars emitting more carbon emissions and creates even more congestion.

Technology:  Cars that fold up and into each other. With this technology, multiple cars can fit into one parking spot.  The cars would be city owned and would be shared throughout the community.

Stakeholders:  Everyone who drives a car.  Also, city officials who would be tasked with regulating this.  Pedestrians and bikers would also be stakeholders as they would benefit from less congested roads.

Implementation:  This would require a mass adoption of new transportation system that may be slow to implement.  In an ideal scenario, the city would own and operate the shared vehicles.  This would certainly be a substantial infrastructure overhaul and would take multiple years to implement.

Source: http://money.cnn.com/gallery/technology/2014/11/11/innovative-city-tech/5.html