Why some buses have one card reader some have two card readers?

When you take bus, you may find that some buses have one card reader some have two card readers. For bus with one reader you just need to tap card once and for bus with two readers, you need to tap twice, tap in and tap off. Why?

The driver tells that this is the station wise charge. Somes routes are relatively long, a bus may need to run more than 1-2 hours for a trip, to charge diffwrent cost is unreasonable. For flat  fare, only need to tap card for one time, the station wise fare get to tap card twice, get on the front door you need to tap card once, when get off the bus from rear door tap card again, the cost between two bus station will be calculated. The bus station wise charge is according to the bus staions a passenger take and get the ticket fare from the background to deducts the corresponding fee. Don't be surprised next time there are two readers the bus, this means the bus fare is is going to be different based on the distance you take. If a passenger does nottap card when get off, he need to bear the price of the whole trip.

How do the two card readers on the bus work

Passengers tap card when getting on the bus, the station start number will be marked, when he tap again when get off, the station number end will be marked. There is a fare table with prices from one bus station to another. If a passenger do not tap card when get off, the price will be made according to the furthest distance from boarding. When the passenger swipes the card or scans the code, the on-board terminal will have an obvious prompt interface to remind the passenger that the transaction has occurred.