When it comes to carpooling, it's not just about the hard cash and fuel prices. 
Let's enumerate all the additional benefits of this mode of transport:
Sharing tolls for highways, entrances, parking lots;
Shorter time of commute, due to lower traffic and so-called high-occupancy vehicle lanes;
Reduction of social exclusion - possibility to travel for people without a car, or elder residents; 
An occasion to meet interesting people and spend your journey time in an interesting way;
Lower CO2 emission, and lower levels of city noise;
Reducing air pollution;  and
Lessening the need for parking lots, contributing to better city planning & bigger green areas.
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