There is an underpass at the intersection of Commonwealth Avenue and the Batasan Road at Sandiganbayan. The underpass is for left turning traffic coming from Batasan to the Elliptical Road-bound side of Commonwealth. I took a few photos of the underpass recently as we were coming from a meeting at the Batasan.
Approach to the left turn underpass – the rightmost lanes of the Batasan Road are for right-turning traffic going in the direction of Fairview.
The underpass has three lanes.
It is well lighted and so motorists are not plunged into darkness unlike some underpasses that are not well-maintained.
Emerging from the underpass, vehicles have enough space to merge with traffic along Commonwealth Avenue.
The underpass emerges as 3 middle lanes along the wide Commonwealth Avenue. There are 4 to 6 lanes to the left and 2 lanes to the right of the underpass lanes. The rightmost lanes are supposed to be for public utility vehicles.
I have not heard of or read anything anywhere about this underpass being flooded during times of heavy rains. These include the particularly heavy rains of Ondoy (Ketsana) in 2009 and the Habagat episodes last year. As such, I believe that the design of the underpass (including its elevation and drainage) is for all weather conditions.