There are 3 feet in a yard and 5280 feet in a mile. By dividing 5280 by 3 you will get the number of yards in 1 mile. 5280/3 = 1760 yards in 1 mile.
To get the answer to your question you need to multiply 1760 by 4 since you have 4 miles, not one. So 1760 x 4 = 7040 yards of highway that they need to pave.