I N F R A R O A D R A I r , t = 100 ∗ e − 3.558 + 1.328 ∗ l n ( G D P P C r , t ∗ 1000 L A N D A R E A r , t ) + 0.239 ∗ l n ( I N F R A R O A D r , t ∗ L A N D A R E A r , t ∗ 1000 P O P r , t ) {\displaystyle INFRAROADRAI_{r,t}=100*e^{-3.558+1.328*ln({\frac {GDPPC_{r,t}*1000}{LANDAREA_{r,t}}})+0.239*ln(INFRAROAD_{r,t}*{\frac {LANDAREA_{r,t}*1000}{POP_{r,t}}})}}
