The end of human civilization can sometimes come fast, and without warning. There may be a situation where people have no time to react, to pack up, and to attempt to flee the cities. As a result, the roads can go for miles with very little activity and many empty cars.
The Caravan as an option for a Stronghold very much depends on the road conditions in your Outbreak Scenario. Either the players are located in a sparsely populated area where travel is frequent or the roads are ‘relatively’ clear for the most part. If you do manage to get a team and a caravan of vehicles going, these are rules you can use to turn your travelling brigade into a mobile refuge from the Outbreak.