Ride sharing is a form of transportation that uses a motor vehicle with more than one single occupant.  Many transportation emissions are due to the high frequency of Single-Occupancy-Vehicle (SOV) trips.  By sharing a ride with even one more person, via carpool or vanpool, the emissions from your trips are cut in half (one vehicle going 15 miles, compared with two vehicles going 15 miles each).  This system is very cost effective, but it is less convenient to the typical campus commuter than driving a personal SOV.  Therefore, campus should encourage ride sharing.