To calculate P¯gl, we first compute w¯gl=wgl/∑glwgl, where wgl is the area weight per intersection. Then calculate the population per intersection: Pgl'=Pgw¯gl. We then use the Pl (LSOA populations) and obtain P¯gl=vglPl, where vgl is the normalised Pgl', ie vgl= Pgl'/∑glPgl'.