If it rolls on wheels, it's 辆

Where the picture shows up in 辆

1. 1

   one at the gate

   门口停着一辆车。

   ménkǒu tíng zhe yí liàng chē

   There's a car parked out front.

   Trains take 列, planes 架, boats 艘. Only wheeled things take 辆.

2. 2

   one you want to buy

   我想买一辆自行车。

   wǒ xiǎng mǎi yí liàng zìxíngchē

   I want to buy a bicycle.

3. 3

   the next one you're waiting for

   下一辆公交车几点来？

   xià yí liàng gōngjiāochē jǐ diǎn lái

   What time does the next bus come?

4. 4

   two coming through

   前面有两辆救护车。

   qiánmiàn yǒu liǎng liàng jiùhùchē

   There are two ambulances up ahead.