In case of going by public transport, if there is no time of wearing Ihram by having a halt at Meeqat, you should wear Ihram in Riyaz before you get on board from there and perform two rakah, but you should not make the intention of Ihram until you are reach nearer to Meeqat then you make the intention of Ihram. It is not permissible to cross Meeqat without wearing Ihram. If you go directly to Makkah Mukarramah, you have to return to any Meeqat like Taif or Jeddah etc and wear Ihram; otherwise you will have to offer dum (qurbani).
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband