What happens to the grit spread on roads and why more has to be spread?

Grit spread on roads primarily consists of sand or salt used to improve traction and melt ice during winter weather. Over time, this grit gets swept away by traffic, rain, and snowmelt, reducing its effectiveness. As a result, more grit needs to be spread to maintain road safety and ensure adequate traction for vehicles during icy conditions. Additionally, the effectiveness of salt diminishes as it gets diluted or washed away, necessitating further applications.