The side of my tree facing the road is brown and dying — what should I do?

Two different pictures depending on how the salt arrived. From spray: browning worst on the road-facing side and heaviest on branches at plow height, evergreen needles browning from the tip back, buds on that side failing to open, and tufted witches'-broom growth where terminal buds were killed. From the soil: symptoms all the way around the tree — leaves scorched brown along the margins with the center still green, smaller leaves, early fall color, thinning crown, and dieback starting at branch tips. Grass often thin or dead in the same strip. Symptoms appear in spring and worsen through summer drought. Two separate injuries share one name. Spray damage is direct chemical burn: salty slush lands on twigs, buds, and evergreen foliage and desiccates the tissue, killing it outright on the exposed face. Soil damage is systemic: chloride is taken up and accumulates in leaves to toxic levels, while sodium displaces calcium and magnesium on clay particles and collapses soil structure, so the soil holds water the roots can no longer extract. The tree ends up drought-stressed in wet soil and poisoned at the same time. The soil version is the one that kills trees; the spray version disfigures and causes dieback.