The largest contributing factor to these high mortality rates was the growing number of trains in service B many of which were running at faster speeds. As the service grew, it extended distribution through more territory and speed became an increasingly important factor. Also, beginning in the 1890s, railway mail trains began to be heavily used at night, with a considerable number of exchanges made from the moving trains.
There were numerous dangers present for railway mail clerks. Items within the mail car itself could rip loose in a wreck, striking or trapping a clerk inside the car. Gallons of scalding water could pour into the railway post office car from a jolted steam driven engine. Inside the mail car itself oil burning lamps and wood burning stoves proved to be extremely hazardous. Tipped over in an accident, or even a sudden stop, there could be very little in a mail-filled wooden mail car which would impede the progress of the flames.
Wooden cars were commonly used in railway service during this period. These cars were especially susceptible to destruction by fire and impact. Even after the railway companies began to purchase metal cars, they found it financially advantageous to continue using the wooden cars for several more years.