Railroad Classifications Yards

The Goal of a Classification Yard

Industry jobs and work trains convey cars into a classification yard.  Cars are given mechanical inspections by the car inspectors.  Air is released from the brake valves and cars are made ready for switching.

The cars are sorted into various classifications tracks according to their destination.  These classes of cars are called blocks.  Each block has a particular outbound manifest train that typically departs within a scheduled window.  When the time draws near for that particular train to depart, the block is assembled with other similar blocks and added to the outbound train in a specific order.

The classification of cars into outbound blocks can be done by flat switching or by humping.

Key Components of a Classification Yard

• Towers
• Yard Office
• Car Repair Shop
• Locomotive Servicing Pad
• Switching Lead
• Crew staging area
• MOW staging area
• Yard Lighting
• Inbound Tracks
• Outbound Tracks
• Yard Air
• Local receiving/departure yard

Flat Switching

Flat switching is performed in a yard where the tracks appear to be flat to the naked eye.  These tracks are generally actually slightly concave in shape.  They create a very elongated bowl.  This bowl reduces the likelihood of cars escaping the tracks on the opposite end of the yard.  It also reduces the need to apply hand brakes to secure the cars within the track.

Crews engaged in flat switching consist of 3 or more members.  The engineer  controls the locomotives, the conductor will work to separate cars high up on the switching lead.  The brakemen works further down the lead on the switching ladder actually opening the switches to direct each car or cut of cars into the particular classification track that is desired.

There are many variations to this standard crew.  Remote control may be used to eliminate the need for an engineer in the cab of the locomotive, reducing the crew by one, while also likely reducing the overall efficiency of that switch job at least marginally.  Also, if the switching ladder is long or complicated, or if there is a desire for a higher output from the crew, they may have one or more utility employees attached to the crew.  These utility employees can operate as additional crew members.  Often times they are added to a crew on a temporary basis to complete a particularly difficult or time consuming job.

Flat switching into a bowl will generally leave a bit of a mess in the classification track.  There are breaks in the resulting block where cars have not coupled properly or are separated by several car lengths.  Before the track may be pulled and added to the outbound train, the crew must "tie-up" the track which can take several minutes.  A good way to differentiate an experienced switch crew, is by how much time it takes to tie up the tracks they have switched.

Separate crews may work opposite from one another in a classic flat switching yard.  They operate on different radio channels and switch cars into the bowl along opposite leads.  Cooperation and occasional communication is required between the crews to ensure the safety of various crew members working in the bowl.

The Hump Yard

Hump Yard operations are very different than flat switching yards however most supporting activities are consistent with both.  Trains are received on inbound tracks, where the carmen inspect and bleed the air from the cars.  The entire train, or some subsection, is pulled to the hump.

2-3 engines, usually remote controlled from the tower, push the train over the hump at 3 mph.  While being pushed up the hill against gravity, the couplers are compressed which allows a conductor standing at the top of the hill to pull the operating level, which separates the cars.  Having separated the cars, each car breasts the hill and gravity takes hold.  The cars accelerate down the hump toward the bottom of the hill.

As the car approaches the first retarder the computer judges the weight and speed of the car.  The applies force against the side of the wheels to slow the car down.  The amount of speed reduction is carefully calculated so that the car will have enough moment to navigate the subsequent turnouts to is resting place in the class bowl.   The class tracks are divided into groups, each group has a secondary retarder, which further reduces the spee
d of the car as it arrives into the class tracks.  Computer systems in the tower monitor weather and wind to adjust retarding forces accordingly.  The yardmaster watching over the entire operation from the tower can further fine-tune the operation.

A switch crew will run a "trim job" on the opposite end of the classification track opposite the hump.  The trim job is responsible for tie up the class track, staging outbound trains, and other support roles such as spotting the RIP or staging the next cut of cars to be humped.

Humps, Bumps, or Flat

So the debate has raged for many years as to which type of operation is the better option for a particular yard.  Both have their advantages and disadvantages.  Humps are certainly more sexy than flat switching operations, but also prohibitively expensive.

Without going into in depth math lessons about efficiency, it can be safely said that there are certain things which are fairly consistent in all hump operations such as gravity, locomotive speed, labor efficacy, etc.  When fully optimized most humps can switch roughly 3,000 cars per day.  This would be roughly equivalent to approximately 25-30 manifest freight trains per day or an entire train every hour.

There are incredible costs associated with the construction and maintenance of a hump yard making them both operationally expensive and capital intensive.  Recent years have seen a decline in the building of hump yards with several being torn down.  Canadian Pacific's current CEO Hunter Harrison is notorious for shutting down humps in favor of flat switching.  While many have derided those decisions they seem to have proven a good strategy.  While with the CN he downgraded several humps along with other changes in operating strategy that culminated in good financial results.  It seems that if a hump falls under a certain threshold of productivity it no longer makes financial sense to keep it in operation, however that math may vary with the cost of capital and operating conditions.

The days of the hump may be numbered for a number of reasons.  First, it requires a sizable major metro area to generate enough single carload volume to justify the economics of a hump yard.  In the past decades the rail industry has lost market share to truck for these business segments.  Single carload shipments are not always what the modern railroader looks for as their ideal freight compliment.  Most railroads prefer large car blocks and entire unit trains, which have relatively small operating costs compared to the more labor intensive single car shipments.  Higher rail prices and slower delivery time, have increasingly caused shippers to turn to trucks as their primary means of distribution.