Complex sentence: The numbers of Indonesians that took "mudik" or "pulang kampung" travel is quite tremendous, the numbers approximately equal with the whole population of Malaysia hit the road altogether, causing massive traffic jams and a sudden rise of demand and volume of intercity transportation.
Split into simpler sentences: The numbers of Indonesians that take "mudik" or "pulang kampung" travel is quite tremendous. This causes massive traffic jams and a sudden rise of demand and volume of intercity transportation.