Take your time with this riddle! Take a lucky gift!

My lovely friends - CS08,
I have many riddles for you. Take your time with this first riddle. You will get a lucky gift on the last day of the year 2009 if you are the first student who can post the right answer.
Here's one to start with:

"Bìm Bịp and Châu Chấu, along with several of their school friends, were invited for a swim at the CàoCàos' pool. The CàoCàos' house was far away and the kids wanted to drive together to save gas. They went in two car pools and spent the whole afternoon swimming."

Question:
This riddle contain a compound word - "car pools". To solve the riddle, you have to distinguish the meanings of this compound word from the meanings of their separate parts. So, what is the meaning of "car pools" in the riddle above?

Hurry up! Hurry up!
I'm right here waiting for you...

Uyên Phương xxx

According to my knowledge, I know a term that is ... a little different from "car pool". That is "pool car" which means "xe dùng chung". I wonder if you've got a mistake or not??? Is "pool car" the term that you wanna talk about???

To napparte:
Thank you for your quick answer. Good job!
Firstly, I would like to confirm my words before -"car pools". This compound word is in a riddle that I extracted from an original American English material --> No mistake here.
Secondly, this is an English Club, we are due to speak in English in this forum; thus, please use English only. Could you give me an explanation in English? This means that you should make the term clear without using Vietnamese term "xe dùng chung".
With the aim of practicing English, hopefully, I will have your answer again.

Thanks so much.

Uyên Phương

Car pool: Your friends, A B C, and you have your own cars, but you want to save gas money. So you have a deal. You use A's car on Monday, B's car on Tuesday, C's on Wednesday, etc...^^

According to wikipedia
Carpooling (also known as car-sharing, ride-sharing, lift-sharing and covoiturage), is the shared use of a [You must be registered and logged in to see this link.] by the driver and one or more passengers, usually for [You must be registered and logged in to see this link.].
Carpooling arrangements and schemes involve varying degrees of
formality and regularity. Formal carpool projects have been around in a
structured form since the mid-1970s.
Carpoolers use pool members' private cars, or a jointly hired
vehicle, for private shared journeys. The vehicle is not used in a
general [You must be registered and logged in to see this link.] capacity such as in [You must be registered and logged in to see this link.], [You must be registered and logged in to see this link.] or [You must be registered and logged in to see this link.].
Carpooling is also distinct from the use of a company/government or
private vehicle by several pool members but at different times, for
economic or other reasons, such as in a military motor pool, but might involve single occupancy....