「電車が空く【すく】」 と「 電車が空く【あく】」


「電車が空く【すく】」と「電車が空く【あく】」はどう違いますか？  
説明が難しい場合は、例文を教えていただけませんか。




I cannot think of any practical uses of 電車が[空]{あ}く.

電車が[空]{す}く means, as passengers get off, the train gets more and more
spacious. Probably it's more commonly used as

> この電車は[空]{す}いている  
>  Not many passengers are on this train.

Note about [空]{あ}く: it is more commonly used for an individual seat, as in

> この席は[空]{あ}いてますか？  
>  Is this seat available?

