Greetings Jeff!
To provide a buffer from roadside noise, I would recommend one row of dense shrubs and one row of dense conifers. The distance between the shrub row and conifer row should be around 8-12 feet. Forgo the shrub component if you do not have the space to accommodate a two row planting.
More than likely, your soils are probably silty-clay or silty clay loam in texture. With that said, I would recommend white fir, Norway spruce, northern white-cedar, or white pine. Space the conifers 6-10 feet within the row.
For the shrub component, I would recommend red-osier dogwood, silky dogwood, or hazelnut. Space the shrubs every 5 feet within the row.
Depending on the type of planting stock you purchase, spring planting will likely be your best bet for establishing your buffer. The retail cost of trees is quite variable, depending whether you buy potted stock, bareroot seedlings, or balled and burlap trees.
Good luck and happy planting!
