P. A. C. E. Project management, tactical and strategic success, personal achievement, and mission accomplishment all require a well thought out plan. In the EP community we recognize the need for a good advance. The advance validates, invalidates or may significantly impact our primary plan. The security team may need to "adjust fire" based on what the advance uncovers prior to the principal's arrival.
To aid your planning process and consider all options, the military community created the PACE acronym, which stands for:
Contingency Plan, and
PACE planning is a risk and failure mitigation planning process. Your Primary plan should always be your best option and your entire team should know the plan, work the plan and believe in the plan. The plan should include input from everyone involved in the operation if possible.
Your Alternate plan is your "Plan B" that would immediately go into operation if "Plan A" fails due to changes in the operation, the venue or perhaps equipment failure. Sometimes the alternate plan may be part of your surveillance avoidance routine.
Contingency plans can be numerous and are the answer to the many "what If" scenarios your team can imagine and plan for. For instance, you may be en route to a venue when the mission comm plan fails and you need to go to secondary comms. You'll still continue on with the primary plan but switch to an alternate comm plan, which was ideally a subset of your primary plan.
Finally you need to have an Exigent/Emergency plan. This may be an immediate evacuation of your principal to avoid a specific risk and threat or it may be because 5 minutes ago your world suddenly crashed down around you due to an earthquake. In 2010 my team was conducting normal operations according to the plan when an earthquake devastated Haiti. There we were with no comms, no power and no way to get information from outside of our compound. All of our primary comms were gone but somehow FB Messenger was still working off of some open WiFi that still worked. We hadn't planned on Messenger being part of our plan but you have to work a solution with whatever you have. We sent our local team members out on scouting missions and told them to go out 10 minutes in all directions then come back to us. This gave us an impression for just how bad things were and some solid route info for planning our return to residence.
After gathering all that facts that we could, we worked out a PACE plan to get our people from work to their compound. PACE planning has proven to be a simple, easily understood and communicated process.