Heat Orders FAQ
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.
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.
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.
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.
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:
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.
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.
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.
Back to FAQ Page