A construction crew is lengthening a road. The road started with a length of 57 miles, and the crew is adding 2 miles to the road each day. Let $L$ represent the total length of the road (in miles), and let $D$ represent the number of days the crew has worked. Write an equation relating $L$ to $D$. Then use this equation to find the total length of the road after the crew has worked 36 days.

Step 1 ：Let $L$ represent the total length of the road (in miles), and let $D$ represent the number of days the crew has worked. Since the crew is adding 2 miles to the road each day, we can say that the total length of the road is equal to the initial length of the road plus 2 times the number of days the crew has worked. This can be written as $L = 57 + 2D$.

Step 2 ：To find the total length of the road after the crew has worked 36 days, we can substitute $D = 36$ into the equation.

Step 3 ：Substituting $D = 36$ into the equation gives $L = 57 + 2 \times 36$

Step 4 ：Solving the equation gives $L = 129$

Step 5 ：The total length of the road after the crew has worked 36 days is \(\boxed{129}\) miles.