Added a note in "Supply routes", explaining the "spawn on road" HMMWV usage.

Custom-campaigns.md

@@ -333,6 +333,10 @@ The supply route will follow the _waypoints_ of the vehicle group (not the path,
 
 The begin and end waypoints of the path defining the front line route define the origin and destination for convoy routes. Endpoints of the route should be placed on or near roads so that convoys can get moving quickly. If far from a road, units will move from their location off-road to the road one at a time until they have all reached the road.
 
+You may optionally facilitate the spawning of convoys on roads, in order to prevent the potentially long form-up time and to help prevent the convoys getting stuck. This is done by placing a "Scout HMMWV" (a.k.a. M1043 HMMWV Armament) at each end of the supply route. The waypoints of that Scout HMMWV should be put on roads, making sure that the lines between the waypoints are centered on the road. The use of "On road" waypoint type in the Mission Editor may help with this. Also, make that route sufficiently long so that large convoys won’t run out of road to spawn on.
+![image](https://github.com/dcs-retribution/dcs-retribution/assets/89945461/4d301288-4038-40eb-838f-ac44ca029aa3)
+![image](https://github.com/dcs-retribution/dcs-retribution/assets/89945461/51589738-a81e-4bdd-980b-bc0d68d27276)
+
 **Important:** Care should be taken to route the frontline around exclusion zones.  If the center of the frontline location lies in an exclusion zones, frontline units may not spawn correctly. You can view the exclusion zones in the Retribution UI by clicking on the "3 stacked sheets" icon below the ruler icon in the top left corner of the map window. Frontlines can jump smaller exclusion zones but using these can cause frontlines to render on both sides of the gap, or cause the frontline to render far from the intended line.
 
 **Work in Progress**