From D.C driver's manual:
Entering the Interstate
Interstate and other limited access highways are usually reached by an entrance ramp and acceleration or deceleration lane. The entrance ramp gets you going in the desired direction and the acceleration lane gives you the opportunity to get up to the speed of the traffic. When entering an interstate, the solid painted lines that divide the entrance and the interstate should not be crossed. If there is a short entrance to an interstate, where there is no acceleration lane, you should speed up on the entrance only after you have found a gap in the traffic. In general, you should stop before entering an interstate when waiting for a break in the traffic. If entering an interstate from the left entrance, compare what you see in your mirrors with what you see when looking over your shoulder.
