During the morning rush hour of July 9, 1918, Nashville, Tennessee, became the site of one of the deadliest rail accidents in US history. The head-on collision between two passenger trains killed 101 people and injured 171. Many of the victims were laborers traveling to work at a gunpowder plant outside of Nashville. Both trains were traveling at about 60 mph (96.5 km/h) upon impact, and the sound of the crash could be heard as far as two miles (3.2 km) away. What caused the collision? Discuss