thanks for bringing this up. early in the year, i had written to them about vertical separation (multilevel), a few weeks later they responded:
me:
On the landside, BIAL has arrival and departure traffic at the same level and and according to information on BIAL website, there is no separation of incoming and outgoing traffic.
Given, the current and projected air traffic levels in Bangalore, this could potentially lead to congestion on the landside and thus lead to customer dissatisfaction regarding facilities and service at BIAL.
While it may be too late to achieve, vertical segregation, are there any plans of horizontal segregation of arrival and departure traffic?
BIAL:
The landside traffic is planned in line with the concept of the passenger movement in the terminal.
There is a segregation of the departure and arrival traffic planned on the landside to ease the travel of the passengers as well as the visitors.
Hope this clarifies your doubt.
basically, road side is planned in accordance to the layout of the terminal. the terminal and the flow itself will have to be altered to fit a multilevel road side.
BIAL I think designed for horizontal separation , like JFK terminal 4, which opened in 2001, and handled more than 6 mill pass in 2004, now that was the initial design estimate of BIAL. BIAL is already doing that number and more. the question is does this scale?
it is possible that it can still be managed, but it will all depend on the flow of traffic in front of the terminal and how it is managed. BIAL front space is much longer than HAL. any how check the first 400 frames of this...
http://bialairport.com/img/flash/video01.htm
6 lanes in front of the terminal, separated by an overhang in the middle. i am guessing 3 are for arrival and three are for departure. apart from this there is a bus bay. i was trying to understand the flow of traffic but i am not able to get details from masterplan because it is a low resolution pdf.

can you make out how the traffic will flow from this image?

blrsri..
Multi level arrival and departure is very much necessary for many reasons..including better management of the vehicular and people movement
what other reasons, can you explain?