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Heat Orders FAQ

What Is a Heat Order?
It is an order given to railroad engineers to reduce their speed over a given section of track. As automobiles are sometimes requested to lower speeds for various road and weather conditions, trains are subject to the same thing.

Why Is a Heat Order Necessary?

The trackage that VRE trains operate on consists of continuous welded rail. Rails come from the welding plant in strings one-quarter mile long. Once the quarter-mile rails are laid in the track, the ends are welded to each other to create strings of rail that are truly continuous. This eliminates the “clickety-clack” of traditional 39-foot rails. Welded rail results in a smoother ride with less maintenance.

Steel rails slowly expand and contract as temperatures rise and fall. In fact, an 1800-foot length of rail will expand almost one foot with an 80-degree change in temperature! Before welded rail, expansion was absorbed by a small gap (joints) between the rails every 39 feet. With welded rail the normal tendency to expand must be constrained internally by securing the rail. Careful engineering measures, including heating the rail, are taken when rail is installed to account for rail expansion and contraction. The ties, rock ballast, and rail anchors, which hold the rail longitudinally, must be strong enough to keep the rail solidly in place instead of expanding or contracting. Under extreme heat, the rail, on rare occasions, wins the expansion battle and a “sun kink” results. A sun kink causes the track to shift laterally causing a curve in what is otherwise a straight pair of rails.

Normally these stresses are contained by the ability of both the railroad spikes, tie plates and cross ties, supported by the ballast (the stone under the rail and cross ties), to resist the side-to-side movement that causes buckling in the rails. A substantial ballast shoulder at the edge of the ties, and a “full crib” between the ties, are extremely important in overcoming the lateral forces. Additionally, railroads apply anchors at most cross ties to grip the rail and hold it in check, and thus keep the entire track structure in line. However, in some cases these measures cannot hold the extreme amount of force that high temperatures can create. A sudden release of these stresses may occur, resulting in the rapid (and often audible) development of a “kink,”or sideways movement in the track.

That is where the heat inspectors come in. To add an extra measure of safety, track inspectors are sent out when the temperature rises quickly from night to day or when the daytime temperatures become extreme and the rail attempts to rapidly expand. These inspectors look for signs the track is under extreme compression and in danger of kinking out to the side. Signs include wrinkles in the track and disturbances of the ballast. If warranted by the inspection, speeds are lowered for trains, whose heavy weight can set the steel molecules in motion. As an added safety measure, passenger train speeds that VRE must follow are lowered as well.

When a “kink” or high tension is found in the track, the track is taken out of service, repaired, and then put back in service. That is why there are times that we are limited to one track during the summer as repairs are made.

Why Can Freight Trains Go Faster Than Passenger Trains during heat restrictions?

Simply, they can't and don't. Freight trains maximum speed limit is 60mph, passenger trains maximum speed limit is 70mph. During heat restrictions passenger trains must travel 20mph lower than the speed limit and freight trains 10mph lower than the posted speed limit. This effectively makes freight trains and passenger trains travel the same speed. However, as passenger trains slow as they stop and start for station stops, the freight trains do not. Hence why they seem to be moving faster.

How Is it Determined If Heat Orders Are Necessary?

The need for Heat Restrictions is determined by our host railroads. See below for their statements on heat orders.

Statements from CSX and Norfolk Southern:

CSX (from CSX)
Heat orders are issued when the forecast is for temperatures to be around 90 degrees. The effect is to reduce speeds of freight trains by 10 mph, but not lower than 30 mph, and to reduce the speed of passenger trains by 20 mph, but not lower than 40 mph. The intent is to increase the measure of safety in hot weather that might cause continuous welded rail to bend or kink as a way of relieving pressure.

Norfolk Southern (from NS)
Norfolk Southern does not issue blanket heat restrictions or heat orders. NS inspects the track with sufficient frequency in hot weather that if problems are detected, NS orders trains to run more slowly through the affected area until the problem is corrected.

Why do Norfolk Southern and CSX have different policies?
The short answer is that each railroad operates efficient and safe. Railroading is an inexact science and many challenges faced are met in different, but equally effective, ways. The approach to track restrictions in hot weather is one of those challenges.

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