It simply means terrorists will have to wait a few minutes longer. Even though departure times may be changed, in many instances the route traveled cannot, which is the main reason terrorists select the area around the home or office to kidnap or assassinate their victim. If the executive lives in an area with limited access. There may be no routes to change. The farther away from the home or office.
Statistics also indicate the area around the home and office is the most dangerous.
A French businessman was assassinated at his doorstep. A Colombian businessman was kidnapped 200 yards from his office. Within a few blocks of someone's home. If something or someone different enters this environment. This is where the system often fails.