Hi Sri,
It would help to see what the options were (from the drop down menu) for this second question. As is, since the question tells us to assume that the TOTAL traffic over the course of the say is the SAME for each type of vehicle, I would be looking for whichever time has the greatest OVERALL TOTAL for the 4 types of vehicles.
With the two options listed (15 and 16), the "16" has a greater percent...."through trucks" is about the same for both times, "rural cars" AND "urban cars" are higher at "16" and more than offset the drop in "business day trucks" that happen at "16" (relative to "15")
GMAT assassins aren't born, they're made,
Rich