Security is a big deal. Presumably after the hotel bombings in Bombay.*
There's a guard box at the lower left, with metal bars that can be lowered to allow vehicles to pass. When you drive up in a taxi, they ask you to pop the hood and scan the undersides of your vehicle for oddities.
I tried to take a picture of the whole thing; he wasn't very happy with me. They didn't really open the trunk (and I know how big plutonium halves are), so I'm pretty sure this is all security theatre. Also, metal detectors when you enter.
*: I like Bombay better than Mumbai.