Bread crumbs does not only apply to intersections as is shown in the video below.   Riders may have to stop for a variety of reasons, and this can happen on any type of road.  When riding, either in a group or solo, you should always be checking your mirrors frequently.

You are Responsible for the rider behind you, and this applies to every rider in the group.  Bread crumbs are all about making sure no rider gets left behind.  In addition to keeping your one/two second spacing with bikes in front of you, you need to keep an eye on the rider that’s behind you.  If you lose sight of the rider behind you, you need to do one of the following:

1. If the group is turning at an intersection, or there is a turn onto a new road and the group is taking that turn, you need to stop and wait for the rider behind you to catch up.
2. If you’re on a curvy road and you’ve lost sight of the rider behind you, slow down until they catch up, and then proceed to rejoin the group.  Do not ride beyond your or the limits of those with you when catching up with the rest of the group.   
3. If the rider behind you doesn’t catchup, you then need to give the signal to the rider in front of you that the group needs to pull over.  This signal will make its way up to the road captain, and he/she will pull the group over at the next safe location.  Once the group has pulled off the road safely, the road captain leading the ride will phone the sweep and then assess the situation from there.

In the video below, courtesy of http://www.sunsethog.com, you will see that the sweep (last rider) gets caught at a red light and is forced to stop.  The rider in front of him notices that the sweep can no longer see him, so he stops before making the next turn, as does the rider in front of him.  Once the group gets back to a straight road, the entire group is able to get back together.