[Retric]

At high volumes of foot traffic the high cost of sending pedestrians up over a footbridge is greater over the lifetime of a bridge than doing the same to cars.

Consider the physical risks pedestrians takes vs cars over a bridge, the lost time on each journey for cars vs people going over a bridge, fuel costs from additional car trips vs additional fuel cars expend going over a single bridge etc.

Even relatively modest levels of foot traffic pay for a cheap bridge that’s going to last ~50 years.