The train is supposed to have arrived =The train should have arrived =The train was supposed to arrive =The train was to have arrived.都相等嗎?

1. The train is supposed to have arrived.
=（大家現在認為）火車可能已經到站了。（is表示是現在的狀況；被動態動詞suppose: 大家現在的猜測；不定詞用完成式，表示在主要動詞之前發生）

2. The train should have arrived.
=（我認為）火車應該已經到站了。（should: 我的想法）

3. The train was supposed to arrive.
=（大家原來以為）火車即將要到站了。（不定詞用簡單式，表示時間比主要動詞晚：to arrive的時間在suppose之後；was過去式，表示不是現在的狀況）

4. The train was to have arrived.（be + to arrive是未來式的相等語：= will arrive，所以was to have arrived = would have arrived；不定詞用完成式表示發生的時間點比主要動詞was更「早」）
＝火車原來是應該早就到站的。(was表示不是現在的狀況：大家「先前的」判斷）

這些句子在意思有滿大的出入，不能相等。