What is a Heat Order?
A heat order is an order given to railroad engineers requiring them to reduce the operating speed over a given section of track. Just as drivers are warned to slow down in inclement weather, trains are subject to the same speed restrictions, in the name of safety.
The operating railroad’s engineering staff imposes a heat-related speed restriction when the temperature of the air reaches a specific point or if it has been excessively hot for consecutive days. The “slow order” requires train operators to limit the maximum operating speed to 30mph within the affected territory. The temperature at which heat related speed restrictions are imposed can vary depending on the track’s characteristics.
These restrictions are police-reviewed and approved by the Federal Railroad Administration (FRA). While this may pose an inconvenience, the safety of our passengers, employees and the public is our top priority.
Why are Heat Orders Necessary?
Some lines are comprised of continuously welded rail (CWR), which is rail welded together in strings and each string being 1/4 -mile long. When installed, the ends of these rail strings are welded together to create a seamless piece of rail and a smooth ride for passengers.
One challenger with steel rail is that when temperatures rise the steel expands and when temperatures fall steel contracts. For example, a 1,450’ section of unrestrained rail can expand nearly 6” when temperatures rise by 50 degrees. To counteract this expansion/contraction of the rail, several safety measures are employed to limit movement in the track. These measures include heating the rail to de-stress it, anchoring the rail with ties and ensuring there is sufficient stone ballast and wood ties present.
With the steel rail firmly secured to the ties, a compressive force builds within the track structure and the rail. With high temperatures, the compressive force in the rail can build to the point that the track bucked under its own pressure, causing the track to shift suddenly. This is referred to as a “heat kink”, which often occurs due to the vibration and dynamics of a passing train. Heat kinks can cause harsh shifts in tracks which can result in derailments. To safeguard against heat kinks, a heat-related speed restriction is applied.