To be most effective in removing snow, wedge plows must operate at high speeds sometimes as fast as 50 mph and if a spotter does not know the territory or loses focus disasters and derailments can occur as they must constantly be on the lookout for upcoming obstacles (such as crossings, where the plow must be lifted so as not damage and derail the equipment). Interestingly, sometimes in areas which receive large amounts of snow railroads will place markers at crossings, and other ground obstacles, high enough that even in the deepest snow a crew can know exactly where and when a crossing is located.
When most railfans and historians think of railroad snow plows, one comes to mind among all others, the legendary rotary plows. These behemoth machines were fist developed by J.W. Eliot as early as the 1850s, and improved upon by Orange Jull. However, the rotary was not perfected until Jull sold the rights of the rotary design to John and Edward Leslie in 1883. The initial design by Jull worked by using two large fans that spun in the opposite direction of one another at a desired rpm with the two fans working in tandem; the outer-most set sucked the snow into the blades while the second fan deposited the snow out of a chute located above. The Leslies perfected and simplified this initial design by using a single fan which could trap and scoop the snow, and then depositing it out of the chute.
Overall superior to the initial design the Leslie rotary plow was to manufacturers for production and it became the most successful such rotary ever built (the Leslie name was eventually purchased by the American Locomotive Company, Alco). The main advantage of rotary plows was that they could move tremendous amounts of snow and clear lines that were buried in far deeper snowfall totals (even heavy, wet snow) than wedge plows. Not only could the fan design move more snow than the simple wedge, the fan itself was driven by a steam engine, giving it the power to move all of that snow. A rotary still had to be pushed by a trailing locomotive just like a wedge plow. However, it could do so at much slower speeds, which was much safer for the spotting crew who did not have to feel like they were on a roller coaster ride zipping along down the line.
As railroad snow plows go, rotaries did have an inherent draw back.
Because they were steam driven they required a full crew to keep them
operating, not to mention the spotting crew that was also on board.
Being very expensive to operate, and typically only needed where
extremely large amounts of snow fell during the winter season, they were
mostly relegated to western mountain regions such as on the Southern
Pacific and Denver & Rio Grande Western railroads although a few
rotaries could be found on eastern lines as well. Due to high costs rotary plows were only brought out when
absolutely needed but they could put on quite a show if one was lucky
enough to witness them in action. Today, a few holdouts remain but they
are very rare to see.
Even when some rotaries were updated with diesel
technology which made them cheaper to operate, such as the Southern
Pacific's fleet used on Donner Pass, they have lost appeal for newer
forms of snow removal equipment. Today, railroads rely on a host of cheaper alternatives to keep the rails clear such as snow blowers (which can be equipped to ballast regulators, which can also be equipped with traditional plows) and snow
jets, such as those built by Harco and Essco. Jets and blowers are
ideal for keeping switches and yards clear of snow, or for electrified
lines that use third rail and must keep it clear of snow and ice. Still, when the snow is relentless nothing can quite compare to a rotary or wedge plow, which will still be called upon today in those rare circumstances.
Lastly, for more reading about all types of railroad snow plows (rotaries, Jordans, etc.) you may want to consider the book Railway Maintenance Equipment: The Men and Machines That Keep the Railroads Running
from noted author Brian Solomon. Throughout the book's 128 pages
Solomon covers all types of maintenance equipment from tampers and
undercutters to Jordan Spreaders and rotary snow plows. I own this book
myself and have used it as reference material for this site many times.
It's a great read on an often
little understood area of railroading.