In Japan, the sky exposure criterion regulation has been introduced in 2003. According to the regulation, the rate computed for the proposed building layout has to be greater than the regulated rate determined by the site shape and the road space. First we derive analytical expressions for two types of building sky exposure rates. Then we demonstrate that the sky exposure rate regulation leads to higher buildings, separate buildings, split sites and central placement positions. We also discuss the justification of the other regulation such as height limit regulation and landscape plan.