Carpooling decreases the amount of cars used to travel to a place.
Carpools and vanpools can save time.
Vanpools decrease the amount of cars used to travel to a place.
What decreases the amount of cars used to travel to a place?

[1] single-driver cars
[2] motorcycles
[3] Riding a bike
[4] gas guzzlers
[5] energy barrier
[6] Temperature
[7] vanpooling
[8] adding heat