For box-out of concrete carriageway, should square box-out or round box-out be adopted?

Isolation joints are introduced where the pavement contains manholes and other structures. The joints allow independent movement of the pavement and roadside structures without any connection which otherwise could result in damage.

Square box-outs are commonly used in pavement and it suffers from the demerit that cracks are observed to appear at the corners of the box-out. Hence, to prevent crack formation at corners, the use of rounded box-outs could eliminate such occurrence. In fact, some form of reinforcement could be introduced to reduce the crack formation in square box-outs. For instance, fillets or reinforcing bars and fabric could be placed at interior corners of square box-outs to hold the cracks together should cracks grow.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.