This tunnel is already filled in and the earth sown with salt to prevent another one from growing. The concept was expensive and worthy. Build a pedestrian tunnel under the heavy trafficked highway so that pedestrians and vehicles were not using the same place at the same time. Sadly, it quickly became a place for homeless people to pee and a place for the lazy criminal element to wait for unsuspecting tourists to roll. It was a dark smelly place and no one who knew better would use it.
The linked article goes out of their way to avoid mentioning that is was the urine from homeless people and wandering criminals and instead mentions “lack of use as intended”. They don’t want tourists to crystal city (and the new Amazon HQ) to think their new area is unsuitable for the Yuppy crowd.
So… they filled it in and now everyone crosses the street at the cross walks, taking their chances at occasional hit and run.