The SPUI  is a type of interchange where the arterial and ramp entrances/exits are controlled by a single traffic signal.  This type of interchange can be more efficient than a standard diamond interchange and takes up less space.   A variation of the SPUI that has been used extensively in other countries is to replace the signal with a single roundabout. 

SPUI Video  http://www.improvei70.org/4a2_safety_main.html
Bridge Size and Clearance Time  http://tcd.tamu.edu/Documents/SPUI_Paper.pdf