Michael Giberson
Is this an unpriced external effect of shooting off fireworks on July 4?
July 5 tends to have an unusual number of animal-related traffic problems, as pets, spooked by the fireworks on the previous day, have a greater propensity to wander onto freeways.
From Eric Morris at the Freakonomicsblog, “Road Blocks: The Strange Things That Cause Traffic.”
Other non-traffic contributors to traffic congestion mentioned in the article: oil spills, antifreeze, oranges, lemons, livestock, wild animals, abandoned pets, suicides, homicides, discarded Christmas trees, and furniture and appliances including couches, chairs, refrigerators, and stoves.