For SMRT, I recommend TIB 577 K, TIB 634 D and TIB 847 G,
especially TIB 634 D..
634D is baaaaaaaaaad LOL, after transfer to AM it breaks down like
everyday, so if it doesn't break down means you will strike 4D!

On a side note, I would say most 171 buses are worth a try;
*points to 507M*.