One possible theme could be death and the afterlife. If there were deaths on or near the bridge, the story might revolve around the spirits of the dead not being at peace. Another theme could be isolation. Bridges can be isolated places, and in a horror story, this could be used to create a sense of vulnerability for the characters in the story.
I'm not sure specifically which 'jones bridge horror story' you mean. There could be many local legends or tales associated with a Jones Bridge. It might involve something like a ghostly apparition seen on the bridge at night, or a tragic event that occurred there in the past which now haunts the area.
Another theme might be the supernatural. There could be ghosts or other unearthly entities associated with the bridge. Maybe the bridge is haunted by the spirits of those who met a tragic end there. The idea of a cursed place could also be a theme, with the bridge being a source of misfortune for those who cross it or get too close.
One possible theme could be family. Given Shirley Jones' own family life and her roles often involving family dynamics in her movies.
One possible theme could be family. Christmas is often a time when families come together, and Gary Jones might have written about the importance of family during the holiday in his story.
Another theme could be the magic of Christmas. There might be elements in the story that highlight the special feeling of Christmas, such as the beauty of Christmas lights, the joy of receiving or giving gifts, or the hope that the season brings. If Brian Jones is a child in the story, this theme could be especially prominent as children often experience the magic of Christmas more vividly.
One possible theme could be adventure. Since it involves a wagon train journey, there would surely be elements of exploring new lands.
One possible theme could be hard work. As farmers, they would need to put in a great deal of effort into their land and animals.
The themes in 'across the bridge' as an ironic short story could include the futility of hope. The bridge might represent hope for the characters, but the irony could lie in the fact that this hope is ultimately futile. Also, there could be a theme of misjudgment. The characters misjudge what lies across the bridge, thinking it will be better, when in reality it is not. This shows how our perceptions can be wrong and lead to ironic situations.
Another theme might be community. Even in a tough situation like living under a bridge, people might form a unique community, supporting each other, sharing resources, and having their own social structure. So the idea of community and human connection could be a theme. Also, it could be about redemption. If there are characters who have made mistakes in their past, their time under the bridge could be a journey towards redemption, making amends for what they've done in the context of a true - life - based story.
Tragic accidents can play a big part. For example, a bus full of passengers that crashed off the bridge, and now their spirits are said to roam there. Another possible element could be some sort of curse related to the location of the bridge. It might be that the area was considered sacred or haunted before the bridge was built, and building the bridge disturbed something that led to all these horror - related events.